Less Wrong is a community blog devoted to refining the art of human rationality. Please visit our About page for more information.

You Be the Jury: Survey on a Current Event

31 Post author: komponisto 09 December 2009 04:25AM

As many of you probably know, in an Italian court early last weekend, two young students, Amanda Knox and Raffaele Sollecito, were convicted of killing another young student, Meredith Kercher, in a horrific way in November of 2007. (A third person, Rudy Guede, was convicted earlier.)

If you aren't familiar with the case, don't go reading about it just yet. Hang on for just a moment.

If you are familiar, that's fine too. This post is addressed to readers of all levels of acquaintance with the story.

What everyone should know right away is that the verdict has been extremely controversial. Strong feelings have emerged, even involving national tensions (Knox is American, Sollecito Italian, and Kercher British, and the crime and trial took place in Italy). The circumstances of the crime involve sex. In short, the potential for serious rationality failures in coming to an opinion on a case like this is enormous.  

Now, as it happens, I myself have an opinion. A rather strong one, in fact. Strong enough that I caught myself thinking that this case -- given all the controversy surrounding it -- might serve as a decent litmus test in judging the rationality skills of other people. Like religion, or evolution -- except less clichéd (and cached) and more down-and-dirty.

Of course, thoughts like that can be dangerous, as I quickly recognized. The danger of in-group affective spirals looms large. So before writing up that Less Wrong post adding my-opinion-on-the-guilt-or-innocence-of-Amanda-Knox-and-Raffaele-Sollecito to the List of Things Every Rational Person Must Believe, I decided it might be useful to find out what conclusion(s) other aspiring rationalists would (or have) come to (without knowing my opinion).

So that's what this post is: a survey/experiment, with fairly specific yet flexible instructions (which differ slightly depending on how much you know about the case already).

For those whose familiarity with the case is low:

I'm going to give you two websites advocating a position, one strongly in favor of the verdict, the other strongly opposed. Your job will be to browse around these sites to learn info about the case, as much as you need to in order to arrive at a judgment. The order, manner, and quantity of browsing will be left up to you -- though I would of course like to know how much you read in your response.

1. Site arguing defendants are guilty. 

2. Site arguing defendants are innocent.

I've chosen these particular sites because they seemed to contain the best combination of fierceness of advocacy and quantity of information on their respective sides that I could find. 

If you find better summaries, or think that these choices reflect a bias or betray my own opinion, by all means let me know. I'm specifically avoiding referring you to media reports, however, for a couple of reasons. First, I've noticed that reports often contain factual inaccuracies (necessarily, because they contradict each other). Secondly, journalists don't usually have much of a stake, and I'd like to see how folks respond to passionate advocacy by people who care about the outcome, as in an actual trial, rather than attempts at neutral summarizing. Of course, it's fine if you want to read media reports linked to by the above sites.

(One potential problem is that the first site is organized like a blog or forum, and thus it is hard to find a quick summary of the case there. [EDIT: Be sure to look at the category links on the right side of the page to find the arguments.] If you think it necessary, refer to the ever-changing Wikipedia article, which at the moment of writing seems a bit more favorable to the prosecution. [EDIT: I'm no longer sure that's true.] [EDIT: Now I think it's true again, the article having apparently changed some more. So there's really no telling. Be warned.])

After you do this reading, I'd like to know:

1. Your probability estimate that Amanda Knox is guilty.
2. Your probability estimate that Raffaele Sollecito is guilty.
3. Your probability estimate that Rudy Guede is guilty.
4. How much you think your opinion will turn out to coincide with mine.

Feel free to elaborate on your reasoning to whatever degree you like.

One request: don't look at others' comments until you've done the experiment yourself!

For those whose familiarity with the case is moderate or high:

I'd like to know, as of right now:

1. Your probability estimate that Amanda Knox is guilty.
2. Your probability estimate that Raffaele Sollecito is guilty.
3. Your probability estimate that Rudy Guede is guilty.
4. How much you think your opinion will turn out to coincide with mine.
5. From what sources you've gotten the info you've used to arrive at these estimates.

Then, if possible, do the experiment described above for those with little familiarity, and report any shifts in your estimates.


Again, everyone should avoid looking at others' responses before giving their own feedback. Also, don't forget to identify your prior level of familiarity!

If the level of participation warrants it, I'll post my own thoughts (and reaction to the feedback here) in a later post. (Edit: That post can be found here.)

Comments (260)

Comment author: Rune 09 December 2009 02:28:14PM 17 points [-]

What is completely sad (besides this horrible murder case), is the inability of either website linked to present a coherent, rational argument. In fact, I haven't been able to find one website that reveals all facts and then explains them with their point of view in a rational (or even semi-rational) way.

I find this situation almost as depressing as the murder. I couldn't come to any conclusion based on the poor quality of reasoning used on most websites. Wikipedia, as usual, presents a decent collection of facts.

From the Wikipedia article I could only ascertain that Rudy Guede is very likely guilty. My probabilities for the other two being guilty are low (but have a lot of uncertainty), certainly not enough for me to feel that the verdict is correct.

Comment author: loqi 10 December 2009 10:35:29PM *  16 points [-]

I began with zero familiarity with the case.

  1. Knox: 8%
  2. Sollecito: 10%
  3. Guede: 95%
  4. Agree with komponisto: 80%

Rationale for considering Sollecito more likely than Knox: They're linked quite closely here, but there's enough confusion surrounding the case that I can't take that completely for granted. That being the case, it's unlikely-but-possible that one of Knox or Sollecito was directly involved while the other wasn't, and my prior for a male committing a violent rape/murder is a lot higher than for a female.

Guede is clearly guilty. He fled town immediately after the murder. His DNA was found in the victim's body, by far the most difficult-to-contaminate piece of DNA evidence in the case, making it extremely likely he's the rapist. Very low prior on a rape/murder being committed by separate parties.

The inconsistencies in Knox and Sollecito's stories are definitely worth paying attention to. But there are several factors diluting their importance:

  • I already had a reasonably high prior on the prevalence of brutality and corruption in Italian police forces. This doesn't leave me with much faith in their competence, especially when it comes to interrogations.
  • It's known that Knox and Sollecito were intoxicated with alcohol and marijuana at the time. I don't know how many of you have ever been thoroughly trashed on this duo (I'm guessing the number is disproportionately low here), but memories formed under such circumstances are very fragile. I've personally experienced disagreements provoked by divergent recollections of events that had transpired an hour previously. Given that sort of influence, I know I would have a damn hard time reconstructing a coherent narrative of the night's events after the brutal murder of my roommate and several days of interrogation by Italian police.

The DNA evidence against Knox and Sollecito is also worth paying attention to, and is in fact the primary reason my estimate on their guilt is as high as it is. However, this is partially mitigated by a glaring problem with the case: Most of the evidence was collected before Guede was a suspect. If Guede had been identified from the start, the Knox-Sollecito hypothesis may not have been quite so "privileged". IIRC, the DNA of four unidentified individuals was also found on the knife. Plus the doubt wrt the knife matching the wounds. Plus the odds that Sollecito would take a murder weapon back to his apartment and put it away. My generally unfavorable prior wrt Italy's justice system also adds a fair amount of room for uncertainty here.

The fact that Guede wasn't initially identified also provides the police with a mild motive for contaminating the evidence. It's unlikely that such an action would be detected. That said, my prior for this sort of action is pretty low.

Finally, we come to the elephant in the case: The hypothesis that the murder was committed by three people working together, as the result of a sex game gone bad. This reads like a parody of a flailing prosecutor. Contrast prior with that for a "normal" rape/murder... ouch. And it just so happens that the one party implicated by actual, solid evidence is the one party who fled after the crime.

The rationale for my 80% chance of agreement with komponisto is mostly based on "metagaming" his position. He admits to having a "rather strong" opinion on the case, and it seems much, much harder to form a strong opinion in favor of guilt as opposed to innocence in this case. My estimate would be higher, but given how asymmetrical this case appears to me, I can't rule out "initial counterintuitiveness" and/or extra evidence as a possible motivation for posting this in the first place.

I'll read the other comments and post my update later today.

Comment author: loqi 12 December 2009 10:19:20PM 6 points [-]

I've read the other comments, and for the most part, my estimates haven't moved. However, this remark by Psychohistorian jumped out at me:

The fact that the prosecutor is under investigation for previously using crazy psychotic hypersexual homicidal maniac theories without basis does a lot to explain how the prosecutors ended up with such a crazy theory.

Wow, I definitely missed this when I read about the case. The prosecution's theory was already setting off alarm bells. If this is true, that shaves another percentage point or two off of my estimate of guilt for K+S.

In general, I'm a bit surprised how much faith some commenters have in their causal understanding of human behavior and psychology, when that understanding seems to be derived from a process of imagining what they would do in those circumstances. I know that I would certainly try like hell to maintain a coherent account of the night's events, but taking this kind of interpersonal analogy for granted when assessing such a delicate situation strikes me as willingly throwing oneself into the arms of the typical mind fallacy.

Some commenters seem particularly focused on some of the more arcane details of the case, e.g., the toilet. How much can you really infer from this sort of thing? I get the distinct impression that people are falling back on intuitions gleaned from detective shows and mystery novels, which by construction tend to involve cases that hinge on the little things.

Comment author: JamesAndrix 10 December 2009 10:43:40PM 1 point [-]

The estimates I came up with were a lot less confident than yours, but on reading yours they seem more like my intuition. I think I got burned on the calibration test and now I'm avoiding extremes.

Comment author: Psychohistorian 09 December 2009 07:28:40PM *  14 points [-]

5% for the couple, 99% for the first convict. 90% that my probability estimate is close to yours in the sense that you think the two are innocent and the one is guilty.

I'd read a bit about this in the news, and I checked out those sites and wikipedia.

Given the fact that there is no evidence of prior acquaintance of the couple and the man, combined with the fact that the man did not attempt to implicate the couple despite the overwhelming evidence against him, make it very unlikely that they were involved. That, and one person being crazy/desperate/disturbed enough to commit a brutal rape-homicide is much, much more likely than one person and a completely unrelated couple he's never met before being disturbed enough to commit a rape homicide. The defense's response to forensic evidence appeared pretty strong, and the pro-guilt group did not seem like they tried to seriously rebut this (they mentioned that one defendan't DNA was on the bra strap, but failed to mention three other unidentified people's DNA on it as well).

The fact that the prosecutor is under investigation for previously using crazy psychotic hypersexual homicidal maniac theories without basis does a lot to explain how the prosecutors ended up with such a crazy theory.

My estimate of your position was (as I perceived it) largely independent of my own analysis. You mention a number of confounding factors as to why people are likely to be wrong about these things, with no mention of why they might be right, and you posted this in response to their conviction. It would be very surprising to choose a decision you agree with as an example of problems with human rationality.

Comment author: cousin_it 10 December 2009 12:23:14PM 5 points [-]

Thanks, your comment has changed my mind about Knox and Sollecito's guilt.

Comment author: komponisto 10 December 2009 12:48:57AM 3 points [-]

It would be very surprising to choose a decision you agree with as an example of problems with human rationality.

While it may indeed be legitimate to wonder if my having posted this implies anything about my opinion, I'll note that I didn't in this post cite the jury's decision itself as an example of rationality failure, but merely indicated -- in the context of an erupting international controversy and ongoing Internet flamewars --that the whole topic is by nature fraught with obstacles to rationality.

Comment author: Morendil 10 December 2009 08:14:29PM 13 points [-]

Perhaps this is after all a litmus test for rationality, in a different sense than (I suspect) komponisto intended.

I mean, here I am looking at a 100+ comments thread, discussing a highly charged issue, and everyone is thoughtful, respectful, and willing to take others' points into account.

That is... extremely unusual.

Comment author: gwern 10 December 2009 10:30:39PM 6 points [-]

Few of us have had much investment or interest in the case before, I'm thinking. Presented as an abstract almost-philosophical problem, with a common framework of epistemology, it's much easier to discuss well.

Comment author: dhoe 10 December 2009 12:45:38PM 13 points [-]

Having lived for 14 years in Italy, my impression is that several commenters severely overestimate the rationality and fairness of the italian police force.

Comment author: gelisam 10 December 2009 01:10:46AM *  9 points [-]

priors


Amanda Knox is guilty: 75%, Raffaele Sollecito: 75%, Rudy Guede: 25%. I shall abbreviate future percentage triples as 75/75/25.

No knowledge of the case before reading this post. My prior is due to my assumption that trial people know what they are doing, and on the fact that I imagined that the trial was trying to show that the guilty were K+S instead of G.

acquiring information


Reading about G's DNA, which should be rather good evidence: switching to 50/50/75. I contemplated switching all the way to 25/25/75, but I figured there had to be some reason for the new trial.

Reading about the police's claim that the murder was linked to a group sex game; thinking that this would be a ridiculous motive. This made me think that maybe the trial people didn't knew what they were doing after all. Switching to 25/25/80.

Finally realized that the trial was in fact trying to show that the guilty were K+S+G instead of just G, not K+S instead of G. Stopped keeping track of percentages for some reason.

Reading about the police switching from K+S+L to K+S+G, which lowered my esteem of the police even more.

Reading about the DNA of K+S, figured it was natural for a woman and her boyfriend to have DNA all over the woman's own house.

Still trying to understand who was G relative to the others. I think he's a robber now. Definitely not part of the group sex thing. Even worse feelings toward the police.

Over all, the truejustice website seems more emotional than the friends of K website, which surprises me. I would have expected the family of the victim to have calmed down after the original G trial, yet truejustice still seemed angry; and doesn't even seem to be ran by the victim's family at all. They should be a lot less emotional about this than K's friend, which seem to be a lot more clearheaded than truejustice is.

I'm now quite convinced of the innocence of K+S, although I'm too shy to give an actual percentage. 5/5/95, if not more extreme.

Comment author: gwern 10 December 2009 10:48:57PM 1 point [-]

I think he's a robber now. Definitely not part of the group sex thing. Even worse feelings toward the police.

I like the rapist theory. It's not like Amanda was the only promiscuous American collegian around - birds of a feather... And who would rob an exchange student? No, a consensual meeting gone bad sounds like a far more common scenario to me.

Comment author: Mononofu 12 December 2009 11:55:46PM *  1 point [-]

Why would you murder someone just because she didn't wanted to have group sex?

And even if you did, why the hell would you call the police yourself?

Furthermore, this case was decided by a jury. A group of average people with no real juristic knowledge at all. Just some random dumbasses who couldn't care less and just want to get home (no, I'm not narcist. Just consider: 50% of all people are by definition dumber than the average, and a jury is randomly selected. ie the average jury ranges from IQ 80 to 120, while a professional judge should start at about 125.) Do you really believe they would come to the correct decision?

And just think of the charges against the prosecutor (about inventing crazy conspiracy theories) . .

I guess for me its 5/5/90 for K/S/G.

Comment author: gwern 13 December 2009 12:16:07AM 0 points [-]

Why would you murder someone just because she didn't wanted to have group sex?

Not sure what you are thinking, but to clarify: I meant an encounter between just Meredith and Guede, nothing to do with Knox or Sollecito. I could see a single guy (Guede) expecting sex and then resorting to rape and then murder to cover it.

(And I suspect the jury is on average better than the populace, since just about every country gives into the temptation to lard on extra conditions like 'if you're a felon you forfeit forever rights such as being on a jury or voting', which would disparately affect the lower percentiles.)

Comment author: Mononofu 13 December 2009 01:36:17PM 0 points [-]

Ah, I thought you referred to an encounter between all of them. In this case, I agree with you - that's also what I think happened.

Regarding the juries: I've read to many reports about bad juries than to believe in them, and the fact that they are almost certainly less educated than a judge still remains.

Comment author: Jack 13 December 2009 01:41:00PM 0 points [-]

The Italian system is different from ours. This particular jury included two judges.

Comment author: wedrifid 13 December 2009 01:54:26PM *  2 points [-]

The Italian system is different from ours. This particular jury included two judges.

That's an interesting variant. There may well be advantages to such a system to counterbalance the disadvantages. I know, for example, that I just felt my 'confidence of innocence' adjust itself downwards. (I would expect a judge to be more likely to be corrupt than a random citizen but also to have less naive vulnerability to obvious manipulations. The latter is relevant here.)

Comment author: TraderJoe 09 October 2012 07:04:57AM *  0 points [-]

[comment deleted]

Comment author: erica 16 December 2009 09:08:41AM 7 points [-]

Familiarity pretty good - I've read the Wiki page, revisited several articles from when the murder was first discovered and I watched Sky news the day of the verdict and saw/heard Prof of Criminology, feminist journalist, UK barrister and two Italian barristers. I frequently search the web, hence I found this site.

(I don't understand the up/down system.)

I find the logic of the murder disturbing - if the murder was a game gone wrong, then it was not premeditated, so unlikely gloves were worn. If bleach was used to clean, then why was Guede's DNA all over the body and room? The only DNA evidence for Raffaelle is highly suspect and a physical impossibility to leave DNA only in that one place I would think. That really is the beginning and the end of it.

The Prof of Criminology's view I have to take seriously. But, in saying that Amanda's diary reads like a gap-year Rosemary West he failed to draw contrasts as well as comparisons. Rosemary West was severely abused from early chidlhood, she did not study languages or develop an interest in creative writing.

I have an alternative scenario - a young woman from a comfortable secure All-American upbringing, who has no idea of the level of corruption and politicking in the world, visits Italy and discovers the magic of old Europe and the unexpected appeal of herself to Italian men - the intoxicating culture of Italy, the constant calls of 'Ciao Bella' from men lounging in doorways - and, being naive and unwordly, behaves carelessly and without circumspection not realising that beneath the relaxed veneer of Italian culture lies a strict code of conduct, especially for women. Amanda has behaved exactly as you would expect of an innocent girl with that background - she simply could not comprehend that she could be convicted for a crime that she did not commit and didn't take her interview with the police seriously.

Given the above scenario, when asked to imagine what might have happened that night, Amanda may well have enjoyed being able to apply her obvious interest in macarbre story telling. I myself wonder at the violence depicted in much fiction but being able to express the human condition in fiction is important and we should not rush to criminalise the use of the macarbre in fiction.

I don't want to cast aspersions but I found it very strange that Meredith's parents did not talk at the press conference and I started to find their silence spooky rather than dignified. I also think that Meredith had made it clear to her family that she did not at all like her flatmate's arrogant American 'no one can touch me' attitude. Supposing the Italian barrister dangled the potential for millions in compensation in front of them? How would they feel?

And why does Meredith's mother now say that querying the verdict is making her unhappy? Would she not care if an innocent went to jail? And surely the pain of her daughter's death is not going to disappear from her mind even when the story disappears from the media? It starts to sound more like a desire for revenge than for justice.

Finally, I've worked with about a dozen Italian professionals and was astounded by their anti-American feeling. There have been US bases in Italy since WWII and Italy led the anti-Iraq war movement with their colourful Pace flags.

I don't know what Amanda and Raffaelle were up to that night. I think they were in the first bloom of attraction to each other, on drugs (perhaps more than just cannabis), and not being particularly sensible. But the case is not beyond reasonable doubt, neither is accusing the other, and they have served 2 years in jail already.

PS. this site is a very welcome find - it seems that many, many people these days prefer 'opinion' to logic or standards - I call it the Strictly Syndrome - a cult of personality combined with sectarian affiliations - it's really quite scary to hear how little people care about evidence, universal standards or intelligent debate nowadays. Bring back the Enlightenment, I've had enough of postmodernism!

Comment author: RichardKennaway 16 December 2009 10:46:47AM *  7 points [-]

And why does Meredith's mother now say that querying the verdict is making her unhappy? Would she not care if an innocent went to jail?

I've often seen that pattern. When someone is murdered and someone is convicted for it, the bereaved insist, no matter how controversial the trial, that justice has been done and that any querying of the verdict is an insult to the memory of their loved one.

It's completely barking mad, but then, people are crazy.

(Edit:) And welcome, erica.

Comment author: DanArmak 16 December 2009 11:02:05AM 2 points [-]

In fact, the bereaved normally do this before and throughout the trial, and sometimes continue afterwards even if the accused are not convicted. The media loves displaying them during the trial.

Comment author: erica 18 December 2009 11:07:43AM 0 points [-]

Thanks for the Welcome. I laughed at the illustration.

  • I'm in the UK, are most other people in the US?
Comment author: erica 18 December 2009 12:21:24PM 1 point [-]

Thanks for your replies. Orientation increased to 37% :)

Comment author: whpearson 18 December 2009 12:02:20PM 0 points [-]

Most but not all. There is a small contingent of UK people, myself included. There were meet ups for a bit in London, but those have fallen by the wayside recently.

Comment author: wedrifid 18 December 2009 12:01:00PM 0 points [-]

I'm in the UK, are most other people in the US?

Somebody posted a breakdown by country a while back. You can probably find it in the search. I think the US was the largest group by raw count.

I'm from Australia by the way. Also, welcome.

Comment author: Yvain 11 December 2009 04:58:00AM *  7 points [-]

I averaged up the answers given so far in this thread for Knox and got 35% mean, 20% median.

Comment author: Cecil 11 December 2009 05:57:11PM 3 points [-]

Is this an arithmetic mean or a geometric mean?

Which is the correct mean to use for averaging probabilities, anyway?

Comment author: Douglas_Knight 11 December 2009 08:44:16PM *  3 points [-]

Is this an arithmetic mean or a geometric mean?

Which is the correct mean to use for averaging probabilities, anyway?

The arithmetic mean of the log odds is pretty natural. It is 27%, but the median looks like 30% to me.

Comment author: jimmy 11 December 2009 07:00:01PM 1 point [-]

Neither really, but there's no easy way to do it.

The mean has the problem that if a lot of people claim near ignorance (like I did), then that counts against Knox, when really, it doesn't mean anything.

The problem with the geometric mean is that it is biased towards the low end of the spectrum, so it depends on if the statement is negated or not. (GM(.001,.999)<4%)

The median is probably better than both, but it's still not the right way to do it.

Ideally you'd try to count up how much evidence each person saw and add those, but it is no easy task to estimate how correlated the evidence is (though it's probably a worthwhile subject to put thought into, since thats how you determine how much an additional persons belief is worth)

Even with a large degree of overlap, this is probably one of the cases where sharing beliefs should make everyones beliefs more extreme.

I'd sorta like to see what it'd look like on round two.

Comment author: TraderJoe 09 October 2012 07:03:32AM *  0 points [-]

[comment deleted]

Comment author: Sinai 09 October 2010 03:58:14AM *  6 points [-]

I arrived at the site from the HP fanfiction after reading the author's notes concerning the case.

Probability estimate that Amanda Knox is guilty -- <1% Probability estimate that Raffaele Sollecito is guilty -- <1% Probability estimate that Rudy Guede is guilty >99%

Knox and Sollecito's alibis are contingent on the other. However, I recognize that there is a probability that one may lie to cover the other, so it is not implausible that one may be guilty without the other being so. While they certainly had the opportunity to murder, there appears to be neither motive nor weapon. The only credible evidence against Sollecito is his DNA being on the bra hook material, and there's a great deal of controversy regarding that specimen. The knife thing is just stupid. I have had roommates, and I can guarantee you there are DNA traces of both me and my roommate on pretty much every knife we've ever had. Frankly, the only reason I'm judging Knox's probability of being a murderer being so high is that they're two girls who shared a bathroom, so she automatically has motive.

I recognize that having read the author's notes, I am biased to believe that Amanda Knox is innocent. That being said, I am completely unfamiliar with the case. I went to the pro-guilty site first, where I had a great deal of difficulty discerning relevant information. I spent approximately 20 minutes navigating the site, growing more and more convinced that Amanda Knox and Rafaele Solecito were not guilty because of the near-impossibility of finding relevant facts that pointed out to their guilt. I then went to the pro-innocent site, and spent about 5 minutes there, which confirmed what I suspected; that the evidence against said defendants was completely circumstantial. I then proceeded to read approximately 1/2 of the Massei report, which struck me as rather biased, which made me very sad when I realized he was the presiding judge in the case. Regardless, by that point I was convinced the prosecution had no case, and was largely built on inconsistencies in Amanda Knox's testimony. I was then annoyed to realize that much of the case had to do with Pretty White Girl Syndrome, because however little evidence there was against Amanda Knox, there was even less against her boyfriend Sollecito. I the proceeded to the Wikipedia article, because let's face it, there's really no better place for an overview of the whole shebang . At this point, I'm pretty much offended at this travesty of justice. The evidence against these two defendants seems to be, "they did not have completely time-consistent alibis" and some bum says he saw them together near the murder scene.

edit: I am basing my probabilities on two primary factors: 1) I saw no evidence that Knox or Sollecito were at the crime scene and their alibi seems eminently plausible to me and 2) The pro-guilty site seems batshit crazy.

Comment author: rmjohnston 09 October 2010 08:39:15PM *  3 points [-]

I'm here similarly after reading the aforementioned author note.

There's no legitimate controversy regarding the bra clasp. The clasp was cataloged six weeks after the murder and after being handled by multiple investigators. Sollecito had, of course, visited the apartment multiple times in the two weeks prior to the murder investigation beginning, so his DNA was present in the apartment. The DNA found on the bra clasp was entirely consistent with contamination, and the circumstances under which the clasp was cataloged make contamination inevitable. No reputable judge would ever allow the jury to consider the bra clasp as evidence.

Given the lack of any other evidence against Sollecito and the compelling evidence against Guede, no rational person would attribute any weight to the bra clasp.

Anyway, I'd heard about the case before, but hadn't followed it.

There's no physical evidence against either Knox or Sollecito, the inconsistencies in their statements are classical examples of the inconsistencies brought about by sleep deprived intimidation and interrogation by the police, and all the "theories" about how they participated in the murder and covered up the physical evidence of their participation are tin-foil hat material. And there's an absolutely compelling suspect who isn't them.

Probability that AK is guilty: indistinguishable from 0%. Probability that Sollecito is guilty: indistinguishable from 0%.

Given that Guede was in the apartment at the time of the murder (admitted by him), his DNA was found inside the victim, he initially offered a ridiculously implausible story about how the murder happened ("Guede claimed he suddenly needed to use the bathroom, and while he was sitting on the toilet listening to his iPod, a stranger entered the cottage and attacked Meredith. Guede said he emerged from the bathroom and grappled with the stranger, who ran off into the night after shouting "a black man found is a black man condemned.") and changed his story to name Sollecito once he knew the police and prosecutor's "theory," and the supporting DNA evidence against him that can't be explained by visits to the apartment prior to the murder:

Probability that Guede is guilty: > 99%, with some distinguishably greater than 0% but not significant chance that his initial implausible story was true.

Comment author: lackofcheese 09 October 2010 12:45:07PM *  1 point [-]

I had much the same experience as Sinai. Personally, though, I didn't bother to try this test after having already been biased by Eliezer's opinion on the matter.

Also, I feel that the uselessness of the linked pro-guilt site hurts the overall experiment too much. I know it wasn't translated at the time, but using the Massei report as Sinai did makes the test much more effective.

Comment author: komponisto 11 October 2010 07:20:08PM *  0 points [-]

I know it wasn't translated at the time, but using the Massei report as Sinai did makes the test much more effective.

It's not just that it hadn't been translated; it hadn't even been written!

It came out in March, around the same time as Bruce Fisher's excellent Injustice in Perugia site went up. If I were proposing this experiment today, those would be the sources I would use (i.e. the Massei-Cristiani report for pro-guilt, and IIP, including the appeal summaries, for pro-innocence).

Believe it or not, True Justice for Meredith Kercher represented about the highest quality pro-guilt advocacy available at the time of this post.

Comment author: PlaidX 09 December 2009 06:38:48AM *  6 points [-]

Never heard of the case before, after reading the wikipedia page on the crime and its associated discussion page I think it's very unlikely that knox and sollecito are guilty. Certainly the evidence does not seem at all sufficient to convict them, and interrogating someone for 14 to 30 hours without recording the interrogation is downright idiotic.

I expect you agree.

I'd like to see more posts of this nature. This site has too much theory and not enough practice.

I guess we were all guilty, in a way. We all shot him, we all skinned him, and we all got a complimentary bumper sticker that said "I helped skin Bob".

Comment author: Eliezer_Yudkowsky 09 December 2009 08:04:30PM *  16 points [-]

On a cursory reading of Wikipedia the obvious interpretation is that Knox and Sollecito are innocent and Guede is guilty. I didn't go through all the sites so I don't know if this would qualify as a litmus test, and assigning probabilities in this state of knowledge would be extra work.

EDIT: Read comments and am surprised at how many estimates of "Knox and Sollecito probably didn't do it" have probabilities in the range of 40% attached that they did. If it were a binary judgment or a confidence interval, then yes we should avoid extreme probabilities and widen intervals to compensate for known overconfidence biases. But in this case the hypothesis space of equally plausible possibilities is large, and some low-probability symbols were used to write the message (multi-person rape-murder vs. single-person rape-murder, female rape-murder vs. male rape-murder). It may not always be easy to unravel crime scenes (though this one sounds pretty straightforward) but to focus on Knox or Sollecito seems like privileging the hypothesis.

Unless there's major prosecutorial evidence not in Wikipedia, then this seems like a case of paying too much attention to other people's opinions (the jury, in a case where we have further information that the verdict gained media attention as possibly inaccurate), and I would suggest that anyone who gave a probability higher than .15 be more arrogant in the future.

If, of course, I just haven't done enough reading, then ignore the above.

Comment author: Eliezer_Yudkowsky 20 October 2011 07:42:09PM 8 points [-]

I would suggest that anyone who gave a probability higher than .15 be more arrogant in the future.

This does not mean my assigned probability was 15%. It means, "Even after accounting for fudge factors and people using different numbers to express similar emotional degrees of certainty, if you gave a number higher than FIFTEEN PERCENT it means you've got a MAJOR problem with paying WAY too much attention to really lousy evidence, what other people think, and the authority of idiots."

Comment author: lessdazed 21 October 2011 03:05:10AM 1 point [-]

The most important lesson here has nothing to do with innocence and guilt, but with people's confidently paraphrasing the opinions of others.

How much the more so when those opinions aren't saved as text, both to give the interpreters another chance to parse properly and to introduce the possibility that they could be embarrassed if later shown wrong.

Comment author: imaxwell 10 December 2009 07:32:11PM *  2 points [-]

The main reason my estimate is so high is because

  • I know my information came from two heavily biased sites, and

  • I found the "innocent" site a lot easier to follow and therefore paid more attention to it, so I know my information is particularly biased in that direction.

That said, I did consider a more-arrogant probability of 0.25 or so. My caution in this case isn't on general principle, but because I have something of an old history of embracing cause celebre cases like this only to decide on further reading that the person I'm defending is guilty as hell.

Comment author: saliency 10 December 2009 08:40:06PM 1 point [-]

I agree with Eliezer but like Maxwell's point about assigning extra probability to Knox and Sollecito because the guilty argument was so poorly formated. "She was convicted but I don't get why, perhaps I don't understand this."

That said I think 15% or less more then accounts for this uncertainty. I gave Knox a 6% probability.

Side note, I am surprised that more people are not assigning probability to the chance that none of them did it.

Comment author: AnlamK 10 December 2009 09:53:16PM *  4 points [-]

Would anyone actually be up for discussing the specifics of the case? (I don't know why but I find myself oddly interested in this case.)

As far as I can tell, the biggest pro-defendant evidence is that there is no major DNA evidence of Sollecito and Knox in the room where murder took place. We are told that there is a bra clasp with Sollecito's DNA and a knife that has both Amanda's and Kercher's DNA - both of these DNA traces are 'weak' in the sense that they are not that obvious, require a hefty search and are hard to see in lab. On the other hand, there are 'strong' traces of Guede's DNA in the victim's blood and in the room.

So, the first thing that worries me is that if it were a crime committed by three people, why would you have one person's DNA everywhere in the room and yet two others' only faintly there?

Again, this is the strongest pro-innocent (for Knox and Sollecito) argument that I have - and the one that convinces me most likely that Sollecito and Knox haven't done it.

I don't know - can anyone else site cases in which there was a group murder and yet only a single person left behind 'strong' traces of DNA? Maybe this isn't so unusual after all.

On the pro-guilty side, I must admit that I find Knox's and Sollecito's behavior the morning after the murder and during the investigation a bit strange. If 'Meredith was [her] friend', as Amanda Knox says in her trial, why were she doing cart-wheels during the investigation the morning after the murder? Shouldn't she be distraught and upset like all of other Meredith Kercher's friends? Accuse me of the mind projection fallacy but I feel like I would be distraught (and in a bad mood) even if the victim wasn't someone I knew.

But again, strange behavior isn't really an evidence. It's just something that makes one suspicious and raises uncertainty.

I can't find that many pro-guilty arguments. There are some tidbits that have a lot of uncertainty in them: i.e. Sollecito (allegedly) bought cleaning supplies the night of the murder allegedly again to clean up the murder mess, Sollecito claimed to be using the Internet at the time of the murder but his ISP records indicate otherwise, a woman claims to have heard three people running down that street that night.. etc. None of them as strong to make a case.

Besides these, a few other thoughts:

I really don't know how Sollecito and Knox got linked to this murder. How did they get dragged into this in the first place? Is there really evidence for the fact that it was a satanic sex-orgy gone wrong as the prosecutor claims it is? I mean, this satanic sex-orgy idea seems to be the prosecutor's imagination - there is no evidence for it.

Also, supposing Guede did it alone, would there be additional penalty or a reduction in penalty for him if he were to simply confess?

This whole thing seems to be like a backlash of conservative Italians' against whom they deem the immoral, selfish and arrogant youth. I have a hunch that the Italian prosecutor wants to punish Sollecito and Knox for a lifestyle he considers wrong.

I don't know what anyone else feels but the uncertainty of the case is somewhat disturbing. I wish there was a knockdown evidence and I could know the truth and be done with it instead of this restless search. Any else feeling that way?

Comment author: jenmarie 11 December 2009 02:18:06AM 9 points [-]

I, too, find myself oddly fascinated by the case. I assumed Sollecito and Knox were guilty until just before the verdict came in, when the story was gaining more traction here in the U.S. I can't recall what it was that I read that made me question their guilt, but it set me off on a quest to learn as much as I could about it. I've basically taken details reported in the media, blogs, etc., that disturbed me and looked for the defense's OR prosecution's take on that detail. Here are the main points, and what I understand to be the truth behind the "evidence" - listed in no particular order: I wish I could provide sources, but I haven't kept track.

  • One of the main things that I keep in mind as I read about the case is that the prosecution leaked many details to the public which have since been proven false and public opinion was turned against Knox & Sollecito very early on based on a lot of incorrect information. The same incorrect information still abounds on the internet and in many minds.

  • Bleach. I had read a number of times that Knox and/or Sollecito had purchased bleach around 7 AM of the morning following the murder. I'd even read that there were receipts confirming this. However, upon further investigation, I've read a few things refuting this. Most importantly, there was no mention of bleach in the prosecution's case. Supposedly there IS a receipt, but it's dated a month before the the murder.

  • DNA. I tend to believe the defense on this. The miniscule amount of DNA on the victim's bra clasp and the miniscule amount of victim's DNA on the knife blade cannot be discounted as contamination in the lab. Also, if there was really a sex game gone awry as the prosecution claims, you'd think there'd be a whole mess of DNA from all parties involved. And as to the presence of Knox' DNA mixed with the victim's DNA in the bathroom, well any rational observer could explain that as a normal consequence of cohabitation. On the other hand, there appear to be abundant examples of Guede's DNA throughout the crime scene.

  • Guede's confession. I'd read that he did NOT implicate Knox or Sollecito in his original confession. But later (presumably after he had been made aware of their status as suspects) he changed his story to include them. Naturally - as their involvement would be very useful for scapegoating the actual murder.

  • Knox' "confession" and implication of the innocent Lumumba, her boss, which many take as a sign of her guilt. I'd read that the police used a text message she'd sent earlier in the evening to Lumumba, after he'd given her the night off, which said "see you later." Apparently, the Italian police took this to mean they had an actual appointment to see each other later, instead of as a generic farewell. I'm assuming the police were considering Lumumba as a potential suspect, and I wouldn't be surprised if their line of questioning when interrogating Amanda led to this suggestion in her mind as well.

  • Knox' behavior. This is where the trial strikes me as most ridiculous. The fact that she turned cartwheels after police questioning doesn't really surprise me all that much. Perhaps this is how she alleviates stress. Who knows. I'd probably think it was a little weird, but certainly not evidence of guilt. She was seen buying "lingerie" (underwear) a few days after the murder, and she was with Sollecito. Well, as it turns out, she was shut out of her apartment and had nothing but the clothes on her back. I'd probably run out to buy underwear right away too. And as to the suggestive remark Sollecito was overheard making, well, so what. He claims it was in jest, and that wouldn't surprise me at all ... again, like the cartwheels, maybe a little humor alleviates their stress.

  • Knox' sex life. I'm shocked at how irrelevant it is to this murder case. She was (falsely) told she was HIV positive while in jail so that she'd give up the names of her sex partners, which totaled 7. 7 partners In her entire life, not in the weeks she'd been in Italy. Again, it's irrelevant, but many minds were poisoned against her by little tidbits like this.

  • Knox' character. You'd think that there'd be signs of something not quite right in a person who could do as the prosecution alleges. Yet in interview after interview, Amanda's friends, family and others who knew her could not point to anything that might reveal a side to her character capable of such horrific acts. I recommend reading this article, http://www.friendsofamanda.org/files/Radar_Knox.pdf, - linked from the FOA site - especially for the quotes from Lisa Pasko, a criminology professor at the University of Denver who specializes in young women who commit violent crimes. "If Amanda Knox is guilty, says Pasko, “this crime goes against everything we know about criminology.”

Based on all of the above, I believe the probability that Knox and Sollecito are guilty of Kercher's murder is extremely low.

Comment author: AnlamK 11 December 2009 06:21:31AM 2 points [-]

Thanks for your summary.

The only place I differ from you is the cartwheel part. This behavior strikes me as genuinely insensitive and disrespectful but being disrespectful and insensitive doesn't make one a murderer.

I'd like to believe that the prosecution has a case but for the life of me, I can't see one.

One thing that struck me as weird is that Kercher's family was 'pleased' with the verdict - do they really think that Knox and Sollecito took part in the murder? Why do they think that way? I'd like to know. Surely, the Kercher family must be reasonable people - so why are they pleased with the verdict?

The horrifying prospect is: do they know something I don't? If so, I must search for it and learn it... :-(

Comment author: Cecil 11 December 2009 06:11:12PM 4 points [-]

In response to the cartwheel part - here's a possible explanation. It's from a pretty clearly biased source, but it does sound reasonable. http://perugia-shock.blogspot.com/2009/03/amanda-knox-finally-admits.html

At the very least I doubt she was leaping around exuberantly and spontaenously.

Comment author: AnlamK 11 December 2009 07:31:44PM *  2 points [-]

From the link you give:

She told him she could go even more and showed him. He asked why she was so good at stretching and she explained she had been doing gymnastic when she was younger. So he asked her if she could do the other things, the cartwheel, the split, the bridge and she showed him.

Thanks for this - one more mystery solved.

Comment author: Jonathan_Graehl 11 December 2009 11:38:08PM 3 points [-]

Why look for rationality in the desires of a typical bereaved family? Surely if they had their way, anyone associated with the event at all would be punished, so great is their loss.

Comment author: Sebastian_Hagen 12 December 2009 08:46:42PM 4 points [-]

I don't know what anyone else feels but the uncertainty of the case is somewhat disturbing. I wish there was a knockdown evidence and I could know the truth and be done with it instead of this restless search. Any else feeling that way?

Oh, definitely. This is a known bias; fight it.

Comment author: michellesings 26 April 2010 07:27:27AM 0 points [-]

injusticeinperugia.com has some current stuff

Comment author: AnlamK 13 December 2009 09:53:33PM 0 points [-]

Thanks for the link! I will try to fight it :-).

Comment author: ChristianKl 12 December 2009 08:39:58PM 2 points [-]

People can behave strangly under pressure when they don't want to except reality. If you were never in a situation which such pressure it's hard to estimate your own reactions to it.

Comment author: michellesings 26 April 2010 07:26:34AM 0 points [-]

Actually she was doing Yoga to calm herself. No lie.

Comment author: GreenRoot 10 December 2009 02:09:21AM 4 points [-]
  1. Knox guilt: 80%
  2. Sollecito guilt: 80%
  3. Guede guilt: 99%
  4. prob of agreement: 0.8

  5. I was unfamiliar with the case before hearing about the verdicts on the news. I spent about 10 minutes on the Wikipedia article, then20 minutes on each of the sites you linked, and made these judgments before reading others' comments.

Guede's guilt seems almost beyond doubt, given the DNA evidence, his implausible story, and his flight without calling police. Regarding Knox & Sollecito, I'm convinced of the prosecution's version of events mainly by the cell-phone record evidence and the many conflicting statements given by Knox and Sollecito over time, with variation that goes beyond my (only moderately informed) expectations for bad memory or coercive interrogation.

Meta-evidence judgments: in the pro-guilt site you linked, it took a while to find concrete info, but when I found the Prosecution's case->Facts Presented section, I found a lot of very specific detail regarding the exact times cell phones were turned on and off and the times and durations of calls made, as well as detail regarding the forensic evidence and the credentials of the experts who testified about it. The pro-innocent site lacked such specifics and didn't seem to account for all the damning details. Both sites seemed very distorted by affection for Kercher (pro-guilt) and Knox (pro-innocence) and their nationalities.

I read the pro-guilt site before the pro-innocent site, and I noticed this causing bias: as I read the pro-innocence site, I felt myself internally "rooting" against them, expecting that they couldn't answer all the evidence and (maybe not surprising) finding that this was so. I tried to adjust for this in my judgments.

I have a low prior for this mix of murderers committing the crime together, and a high prior for a guilty verdict given by a jury, and feel like these two facts approximately cancel out.

After reading others' comments, I was surprised that most others leaned toward Knox's and Sollecito's innocence. I would update my judgments only marginally because of this, because I read the linked sites more closely than others' claimed to. I do however revise my estimate of agreement with komponisto down a bit to 0.6.

p.s. This is a very interesting exercise, which led me to register and comment for the first time after lurking for several months. I am very curious about your (komponisto's) judgment and reasoning.

Comment author: GreenRoot 10 December 2009 07:59:49PM 3 points [-]

After reading more comments, I've updated my probabilities significantly. Here's what influences me:

  1. Different commenters focus on different subsets of evidence. This makes me suspect that my own focal subset was incidental and probably depended on what order I encountered various claims.

  2. Many items of evidence presented as fact (and which I relied on), such as cleaning supply shopping and the contents of the washing machine, are said by others to be rumors and were never presented at trial. This undermined a lot of what I based my judgment on.

  3. The judgment of people who have followed the case very closely (e.g. jenmarle) is that Knox and Sollecito are innocent.

Together, these things make me throw my hands up in the air. I don't think I can clear things up without spending much more time on it, definitely not without seeking out new sources, and I don't know where to look. I now believe: Knox: 50%, Sollecito: 50%, Guede: 99%.

Comment author: Jack 10 December 2009 04:09:21AM 1 point [-]

The cell phone evidence and the changing stories are what gives me reason to a probability of guilty to S and K above .05. (See my comment for my probabilities). The effect of this evidence was mitigated for me by:

  1. Their likely intoxication during this period.
  2. Police coercion leading to confusion about the events.
  3. It looks like a lot of what the pro-guilty site claims ended up being unproven rumors not produced in trial, this makes it very unclear to me what story S and K actually ended up giving in trial. Since the site exaggerates other claims their claims about the cell phones and the stories can't be fully trusted.

You weren't troubled by the lack of motive and the fact that after covering up her involvement in a crime but intentionally leaving evidence of Guede's presence Knox went on to point the finger at someone who couldn't have been involved after being coerced by the police? Shoot, I can't figure out why Knox, if she was guilty, wouldn't have just stayed at Sollecito's until someone else discovered the body.

Comment author: Psychohistorian 10 December 2009 06:31:04PM *  5 points [-]

What I can't understand is, if all three were in it together, given the evidence against Guede, why he didn't rat out the other two in exchange for a reduced sentence. I'd be amazed if the Italian legal system doesn't cut such deals, and I'd be amazed if the prosecutors didn't try to get him to rat out the other two. If they were actually involved, the odds that he'd turn on them in that situation seem well over .9.

Comment author: GreenRoot 10 December 2009 07:40:28PM 0 points [-]

You weren't troubled by the lack of motive...

Hmm, thinking back, I didn't consider motive too closely. I rather got caught up in the evidence of Amanda's evasion. In retrospect, this would lower my probabilities.

...and the fact that after covering up her involvement in a crime but intentionally leaving evidence of Guede's presence Knox went on to point the finger at someone who couldn't have been involved after being coerced by the police?

I didn't judge that evidence against Guede was left intentionally; I could easily have missed details indicating this. Knox's fingering of Lumumba seemed to me to be a natural part of a collection of inconsistent attempts to establish an alibi and deflect suspicion.

Comment author: Jack 10 December 2009 08:54:17PM 1 point [-]

FYI, I've updated in your direction since my first response. Those phone call lengths are driving me nuts.

Part of the suspicious behavior was that Knox didn't flush the toilet (where Guede had used it) the morning she returned. Also, Knox and Sollectio's 'bloody' foot prints had to be luminaled when right next to them were Guede's visible foot prints. And over all, the shear amount of physical evidence against Guede compared to the near total lack of physical evidence against the other two suggests that if there was a clean up they really cared not at all about Guede getting caught. Which is believable, but they did too good of a job. They're intoxicated the night of, come back a few hours later and can distinguish all of their prints from all of Guede's? And they didn't think he had left enough physical evidence (on the victim) that they thought they should leave the toilet unflushed? They appear to have done a really good job cleaning up and a really bad job getting their story straight- which seems inconsistent to me.

Though come to think of it I'm not really sure why the toilet wasn't flushed at all. If Guede used the bathroom before joining Knox and Sallecito killing Kercher, why wouldn't he flush it? Hearing the screaming is actually a plausible explanation for this. Not flushing would make sense if Guede was trying to provide evidence for the story he was planning on telling but that seems way to smart for him. I also don't know why that would be his planned explanation if he was working with Knox and Sallecito.

Part of the problem is that the details of what happened in the room were never released in English (and that might be a good thing) so there may be good reason to think the evidence indicated three people were involved, etc.

Comment author: Psychohistorian 13 December 2009 06:17:49AM 1 point [-]

there may be good reason to think the evidence indicated three people were involved, etc.

This seems to be a major focus of the pro-guilt site, though it isn't really backed up at any level of detail. Were it true, it would increase the probability that K and S were involved, but still far short of beyond a reasonable doubt, I would think.

Comment author: Shalmanese 10 December 2009 12:38:05AM 4 points [-]

my somewhat admittedly sketchy reasoning:

I go to the University of Washington where there is considerable interest in the case. Of the people who have only been marginally involved in the case, most believe that Amanda Knox is innocent. Of the people who are interested in the case, many believe she is guilty. There's an obvious hometown effect here which biases towards innocence so I'm assuming those who look into the case are taking that into account when and still reach a guilty verdict.

Therefore, I assign a 70% probability to Amanda Knox being guilty (+ or - 30%).

Comment author: imaxwell 10 December 2009 07:21:54PM 3 points [-]

Given the information you're going on, that's not a bad estimate. Actually reading on the case may change your opinion dramatically, though; why not try it?

Comment author: jpet 09 December 2009 09:34:43PM *  10 points [-]

I was unfamiliar with the case. I came up with: 1 - 20% 2 - 20% 3 - 96% 4 - probably in the same direction, but no idea how confident you were.

From reading other comments, it seems like I put a different interpretation on the numbers than most people. Mine were based on times in the past that I've formed an opinion from secondhand sources (blogs etc.) on a controversial issue like this, and then later reversed that opinion after learning many more facts.

Thus, about 1 time in 5 when I'm convinced by a similar story of how some innocent person was falsely convicted, then later get more facts, I change my mind about their innocence. Hence the 20%.

I don't think it's correct to put any evidential weight on the jury's ruling. Conditioning on the simple fact that thier ruling is controversial screens off most of its value.

Comment author: Cyan 10 December 2009 01:16:42AM *  4 points [-]

This is a very interesting analysis -- I like your choice of reference set and your Outside View approach.

Comment author: k3nt 15 December 2009 09:23:44PM 3 points [-]

No prior familiarity; thus I started with no information and no particular beliefs about their guilt or innocence either way.

The first thing I saw was that Ann Coulter is convinced that Amanda and Raffaele are guilty. I immediately moved my belief in their guilt way down. When Ann Coulter takes a strong position on a controversial issue, she is almost always wrong.

From there it was mostly downhill for the prosecution, as far as I could tell.

"Later, when a airtight alibi forced the authorities to release Lumumba, they substituted Guede as the third participant in the alleged sex game, even though he had no known connection to either Amanda or Raffaele." That's just stupid. I don't trust the Italian police, or any police, when it comes to high-profile cases. The political pressure to get a guilty verdict is strong. Then, clear evidence that their original theory of the case was wrong came in, and they didn't significantly revise the theory. Not good.

The pro-guilt side keeps promising links to the "evidence," but I'm not finding it. Very irritating.

I don't care at all that their statements were confused. "She was kept up all night, claims to have been hit, and was denied a lawyer and professional translator" -- or so says the pro-innocence site. Sounds like standard operating procedure when you want to get someone convicted, regardless of the truth.

The physical evidence is confusing. I would need to know a lot more about DNA and luminol and so on to evaluate the claims and counter-claims here.

Total time spent, 45 minutes. My conclusion is maybe 10% guilty for these two, but it's a very tentative conclusion and I know that much of it is based on my belief in Ann Coulter's wrongness ... which is the sort of appeal that shouldn't be reliable -- although based on experience it appears to be.

Comment author: DanArmak 15 December 2009 10:43:40PM *  5 points [-]

Sounds like standard operating procedure when you want to get someone convicted, regardless of the truth.

That's what the police always want. Their role in the game of law is being conviction-maximizers. Given leave they'd tile the universe with convicts.

That's why courts have judges who are supposed to be independent of the police. (At least, in the better class of country.)

Comment author: bgrah449 15 December 2009 10:30:18PM *  1 point [-]

The first thing I saw was that Ann Coulter is convinced that Amanda and Raffaele are guilty. I immediately moved my belief in their guilt way down. When Ann Coulter takes a strong position on a controversial issue, she is almost always wrong.

Okay, I'll bite. Could you name a few examples of this, especially the ones that cemented this belief?

Comment author: DanArmak 15 December 2009 10:39:15PM 1 point [-]

For a claim that she is almost always wrong 'a few' examples won't be substantial evidence - assuming she has more than a few opinions. We'd need either an almost exhaustive catalog of her opinions, or a way to sample them in a sufficiently random fashion.

Comment author: k3nt 18 December 2009 05:20:45AM 3 points [-]

Agreed. All that I have is a highly unscientific impression based on my own personal experiences with her. So far she's batting pretty close to 1.000 though.

The fact that the consensus of this community is contrary to Coulter's conclusion I'm counting as one more data point.

Comment author: k3nt 18 December 2009 05:19:14AM 0 points [-]

Oh jeez you're asking a lot. Too many to count. Google her if you feel up to it.

And honestly, I don't really believe this is a serious guide to truth and falsehood. Every time I test it, it comes out right. But I can't run enough tests to know for certain.

Comment author: k3nt 18 December 2009 05:46:31AM 3 points [-]

Actually, I want to thank you (and Dan, below) for making me think a little more carefully about this.

I now think that the constant wrongness of Ann Coulter isn't an accident. She is an almost perfect example of a pure anti-rationalist: someone who will always and only believe things that accord with her ideology. You can predict what she will say about many issues via a simple process.

For instance, take the sentence "Muslims are bad," and apply it simplemindedly to any issue involving Muslims, and you will be able to predict her beliefs. She insists that Muslims had nothing to do with the advance of knowledge; that Islam has never been a religion of peace or tolerance; that Sirhan Sirhan was a Muslim (he wasn't). She writes: "Muslims ought to start claiming the Quran also prohibits indoor plumbing, to explain their lack of it." And on, and on.

Similarly with "liberals are bad." She believes that liberals are always wrong. Among the conclusions she draws: liberals believe in evolution, therefore evolution is false.

I don't know, it's a pretty impressive record she's got going. She will, no doubt, be right about things on occasion, by accident. But I'm starting to feel better about the reliability of my "shortcut to truth." :)

Comment author: Blueberry 18 December 2009 07:13:58AM 1 point [-]

I now think that the constant wrongness of Ann Coulter isn't an accident. She is an almost perfect example of a pure anti-rationalist: someone who will always and only believe things that accord with her ideology.

I'm very opposed to this kind of statement, because one of my core beliefs is that reasonable people can and will disagree on politics. This sounds too much like people calling Bush or Obama stupid when they disagree.

I suspect that you have a strongly opposing political ideology to Coulter's, and this is biasing you against her. I am aware of factual errors in some of her books, especially the ones about evolution, obviously. But assuming that you don't like Coulter and that you disagree with her values, I don't think you can objectively comment on her rationality.

Comment author: wedrifid 18 December 2009 07:20:37AM 7 points [-]

But assuming that you don't like Coulter and that you disagree with her values, I don't think you can objectively comment on her rationality.

That would seem to make being politically polarized a bulletproof protection against people noticing that you are completely irrational. I don't buy that.

Comment author: k3nt 18 December 2009 03:08:59PM 3 points [-]

Do you extend this distrust of statements made about people who disagree with you on politics, to the field of religion as well? Do you expect creationist Christians to be as rational as scientific atheists who accept evolution?

Coulter is not only "conservative," she's also a creationist.

My problem with Coulter is not that she's conservative. It's that she doesn't think about issues independent of her ideology. There are those on the left who are similar.

Comment author: Blueberry 18 December 2009 08:13:38PM 2 points [-]

Do you expect creationist Christians to be as rational as scientific atheists who accept evolution?

Of course not, because that's not a two-sided debate. Politics is.

My problem with Coulter is not that she's conservative. It's that she doesn't think about issues independent of her ideology. There are those on the left who are similar.

But in that case, you could equally well say, "The first thing I saw was that X is convinced that Amanda and Raffaele are innocent. I immediately moved my belief in their innocence way down. When X takes a strong position on a controversial issue, she is almost always wrong," where X is Coulter's left-wing opposite.

If Coulter and X always write rhetoric from one ideological position, I can agree that you could say they were equally irrational, in the sense that they can't think outside their ideology. But I don't see how you could come up with a useful truth-heuristic from that. Ideological does not imply incorrect. Your truth-heuristic of always opposing Coulter seems to be another way of saying "Coulter's ideology is always wrong."

Comment author: mattnewport 18 December 2009 08:56:49PM 0 points [-]

Of course not, because that's not a two-sided debate. Politics is.

I'm curious what you mean by this exactly. Do you mean that politics is something on which rational people can agree to disagree whereas the truth of evolution is not?

Comment author: Blueberry 18 December 2009 09:58:46PM 3 points [-]

Politics, unlike evolution, isn't really a factual matter. Take abortion, for instance: some people have the goal of reducing abortions, some people have the goal of reducing the population, some people have the goal of maximizing women's reproductive choices, and some people have the goal of maximizing fathers' control over whether or not they have kids. Which goal you have depends on your personal preferences and values, though you may have to bite the appropriate bullet for whichever goal you accept.

And even if two people or groups agree on the goal, there isn't enough information for us to know what the most efficient way of getting to that goal. We might have different ethical or pragmatic constraints as we work towards that goal (for instance, not wanting to give the government too much power on our way there). Even if we agree on the probabilities of success for each legislative choice, say, we may have different tolerances for the risk we as a society assume in getting there. The world of politics and legislation is vague enough that there's not always only one right answer (though there may be definite wrong ones).

Comment author: mattnewport 18 December 2009 10:27:27PM 1 point [-]

I think it's probably true that some political disagreements come down to differing preferences and values. It doesn't strike me that the majority of policy debates which account for much of the noise that passes for 'political discourse' can be seen as debates over fundamental values and preferences however.

A significant amount of political debate seems to revolve around what at least appear to be questions of fact about how to best achieve certain broadly agreed upon aims. I tend to think that a lot of politics and political debate is best understood not as a search for truth but as serving other goals not related to the surface appearance but the more thoughtful and better intentioned participants in the debate do generally seem to believe that they are to some extent debating a factual matter, albeit one that is not as clearly settled by the available evidence as the question of evolution.

Comment author: DanArmak 18 December 2009 10:05:27AM 1 point [-]

I'm very opposed to this kind of statement, because one of my core beliefs is that reasonable people can and will disagree on politics. This sounds too much like people calling Bush or Obama stupid when they disagree.

You can doubt k3nt's ability to recognize such cases correctly, but there's no internal inconsistency in his description.

I know that many people - certainly public media or political personas - are, in fact, ideologists of this kind. I can't say about Coulter because I'm not from the USA and know nothing about her...

Comment author: DanArmak 18 December 2009 10:08:31AM 1 point [-]

She will, no doubt, be right about things on occasion, by accident. But I'm starting to feel better about the reliability of my "shortcut to truth." :)

Most real-life issues admit of more than two answers. It's just the political and media approach to paint things as black and white.

In other words: reversed falsehood is not truth. You can't get at the truth by taking the opposite position from Ann Coulter. Because the vast majority of statements don't have a single opposite position.

So while you can judge her always wrong, it will only help you to be right by dismissing her opinions, not by suggesting the right ones.

Comment author: k3nt 18 December 2009 03:08:47PM 0 points [-]

Of course. It's an exceedingly limited heuristic and valuable only in rare circumstances.

Comment author: wedrifid 15 December 2009 10:16:16PM 1 point [-]

I don't care at all that their statements were confused. "She was kept up all night, claims to have been hit, and was denied a lawyer and professional translator"

They can do that?

Comment author: Yvain 09 December 2009 11:37:21PM *  3 points [-]

For Knox, Sollecito, and Guede in order: 30, 30, 95, but didn't find either website or Wikipedia enough to feel like I had sufficient information. I think you probably thought the same.

EDIT: After looking at everyone's comments, I'm revisiting to 20, 20, 95. Anyone else want to edit their comments to say how they updated in light of everyone else's opinions?

Comment author: Mario 09 December 2009 11:02:30PM 3 points [-]

I was unfamiliar with the case. After checking out both links for quite some time, but prior to reading the comments, I estimated:

  1. 80% (Knox)
  2. 60% (Sollecito)
  3. 95% (Guede)
  4. 90% (confidence in coincidence)

After reading the comments, I was a little surprised that the consensus seems to be decidedly against Knox's guilt. The simplest explanation is that I'm just not a very good rationalist, but I don't find that very satisfying. The four parts of the story that I felt were inconsistent with Knox being innocent were:

  1. Knox's initial account of the night. I tend to believe confessions; it's a weakness of mine. With the exception of the wrong black man being implicated, I think the major thrust of it was true. Complete innocence would mean that the entire account was made up, which seems hard to believe, even if under heavy police questioning.
  2. The bra was removed after Kercher's death. Would Guede have done that? I think that evidence is much more consistent with someone cleaning up after the fact.
  3. The body was covered. This is inconsistent with the actions of a rapist/murderer, but very much what you would expect of someone who had a close relationship with the deceased.
  4. Knox did not flush the toilet. She says that she noticed that the toilet contained a deposit, yet she walked away without flushing. Why?

I'm not sure what role Knox had in Kurcher's murder, but I feel very confident that she (and likely, but not necessarily, Sollecito) knew about the murder long before the police were called, and moved to cover it up. I can't see that as anything other than a sign of guilt, unless my understanding of the evidence itself is wrong (which is certainly possible). I can understand if some feel the need for the motive to make sense to find in favor of guilt, but according to Knox's initial account, she was stoned at the time -- which lowers my personal threshold for the expectation of rational action.

Comment author: Jonathan_Graehl 10 December 2009 02:46:13AM 8 points [-]

The body was covered. This is inconsistent with the actions of a rapist/murderer, but very much what you would expect of someone who had a close relationship with the deceased.

I find the above incredible. I'd give it almost no weight.

Comment author: Jack 10 December 2009 03:40:37AM 3 points [-]

1.What I gathered was that the police saw Knox's text message to the bartender and then coerced a confession involving him. The fact that they got this confession when there is no way it could have been him suggests to me that much of the confession could be totally fabricated. For that matter, why would Knox name the wrong accomplice if they knew they didn't cover up Guede's presence at the crime scene?

  1. One of my problems with the supposed cover-up is that if S and K were intoxicated during the crime and likely during the cover-up they A) wouldn't have been able to distinguish between evidence implicating them and evidence implicating Guede and B) wouldn't have been nearly as successful covering up physical evidence as they apparently were.

  2. Perhaps Guede liked her and felt guilty. Part of the suspicion re: Knox was that she was insensitive after the fact. But this would be inconsistent with her covering up the body.

  3. Knox was almost certainly seriously hung-over and not in the mood to go near fecal matter. Also, her roommates testified that she didn't do a lot to keep the place clean in general. I'm also not sure how not flushing suggests guilt.

Marijuana does not undermine rationality to that extent. Reefer madness PSAs considerably overstated that :-)

Comment author: CAS 10 December 2009 03:58:00AM 2 points [-]

I have to generally agree with you (and I'm also surprised that the majority here seems to believe in K+S's innocence.

The other piece that seems strange is why Kurcher's clothing was in the wash that morning. Just seems like something strange to do... a generally messy person doesn't wash someone else's clothing the morning after partying. Who else might have run the washer otherwise?

It's questionable exactly how involved Knox and Sollecito were, but I don't believe that they are completely innocent.

I was unfamiliar with the case but spend about 2 hours reading the two provided links.

Comment author: Jack 10 December 2009 04:48:06AM 3 points [-]

My understanding was that the clothes washing was a rumor and never used as evidence. That said I find the amount of misinformation surrounding the case incredible problematic.

Comment author: Matt_Simpson 09 December 2009 05:57:28PM *  3 points [-]

Just skimmed the two sites. First:

  1. Your probability estimate that Amanda Knox is guilty.
  2. Your probability estimate that Raffaele Sollecito is guilty.
  3. Your probability estimate that Rudy Guede is guilty.
  4. How much you think your opinion will turn out to coincide with mine
  1. p = .45
  2. p = .45
  3. p = .60
  4. We probably agree on which side of .5 these numbers should be, i suspect you are far more confident, which is perhaps understandable if you have a better understanding of the evidence

It's hard to be very confident after skimming for 30-40min. I don't have the expertise or the time to verify many of the statements made by either side, especially DNA evidence and the like, but the prosecution looks pretty weak. The DNA evidence against the defense doesn't seem to hold up, and the fact that the defendant's stories are inconsistent over time show that they have the memory of, well, humans.

I should also mention that I probably have a bias for the defense in cases like this.

Comment author: komponisto 09 December 2009 06:38:31PM *  1 point [-]

I should also mention that I probably have a bias for the defense in cases like this.

Any thoughts on why that might be the case?

Comment author: Matt_Simpson 09 December 2009 07:45:26PM 1 point [-]

I'm more or less a libertarian.

Comment author: rhollerith_dot_com 09 December 2009 07:49:18AM *  6 points [-]

Page one of the site arguing defendants are guilty has nothing that would count as evidence for guilt. When I got to the bottom of the page and saw that there were 24 more pages, I lost patience for the exercise because the low quality of the argumentation on page one (most saliently, the picture of the vicitim when she was five, which if course is not evidence at all, but which will tend to evoke biased thinking in the reader) was a sign that the other 24 pages would be very sparse in actual evidence.

Aren't there enough opportunities for us to practice rationality such that we can check our answers to make it mostly a waste of time to assign probabilities to an event for which it will probably forever be impossible to know "the answer"?

Your job will be to browse around these sites to learn info about the case, as much as you need to in order to arrive at a judgment. The order, manner, and quantity of browsing will be left up to you

If you are going to leave it up to the reader, you should at least tell us where on the 25 pages the strongest evidence is on the site arguing defendants are guilty.

Comment author: komponisto 09 December 2009 08:06:54AM 3 points [-]

If you are going to leave it up to the reader, you should at least tell us where on the 25 pages the strongest evidence is on the site arguing defendants are guilty.

Sorry about that; it's scattered accross the site, which as I said is basically a blog. Try the category links on the right side of the page; such as this.

Aren't there enough opportunities for us to practice rationality such that we can check our answers to make it mostly a waste of time to assign probabilities to an event for which it will probably forever be impossible to know "the answer"?

I believe I know "the answer" with high probability, and want to see what others think.

Obviously, anyone else is welcome to post whatever rationality exercise they wish.

Comment author: AngryParsley 09 December 2009 08:08:30AM 2 points [-]

Page one of the site arguing defendants are guilty has nothing that would count as evidence for guilt.

I agree. A lot of the stuff on that site was just silly. It was mostly appeals to emotion and random stuff like (I'm paraphrasing), "A witness heard people running on some metal stairs, therefore the defendants are guilty!"

Aren't there enough opportunities for us to practice rationality such that we can check our answers to make it mostly a waste of time to assign probabilities to an event for which it will probably forever be impossible to know "the answer"?

I think this is a test to see if we all come to the same conclusion in a case that stirs up a lot of emotions. If komponisto is Italian, he might have vastly different probability estimates than some of us Americans.

Comment author: BlackHumor 05 April 2011 04:05:21AM *  2 points [-]

1.False 2. False 3. True 4. True

Why am I giving (most of) these in boolean terms rather than probabilities? Bayesian probabilities aren't useful in cases where the most probable scenario for (AK guilty) is something like "Two of the perpetrators were secretly ninjas". There really is no rational way to convict someone for leaving no forensic evidence in a room whatsoever.

I have to admit here though that I peeked at your article before posting this. And incidentally, predicted what it would say pretty damn well. (AK not guilty with a probability that reduces to 0, with the other two probabilities also expressible in boolean terms, and on the whole contradictory of the opinion of the jury)

I also have to admit I skipped straight to Wikipedia after reading your article, and found mostly that the facts you gave were correct and thus your argument was sound. My prior probability for any of them being guilty was very low however; around 10%ish. Jury decisions are pretty worthless before an appeal.

Comment author: wedrifid 05 April 2011 04:29:46AM 3 points [-]

Jury decisions are pretty worthless before an appeal.

Jury decisions that prompt public scrutiny certainly seem to be!

Comment author: jenmarie 10 December 2009 07:33:57PM *  2 points [-]

Amanda Knox guilty: .01

Raffaele Sollecito guilty: .01

Rudy Guede guilty: .99

I've become highly familiar with this case since the verdict came down. Over the last 2 years, I've heard bits and pieces about it and all along had assumed Amanda and Raffaele were guilty. I'm a little embarrassed to admit how much time I've spent reading up on the case recently - I think I'm motivated to learn more because I'm perfectly appalled at the amount of misogyny (not necessarily anti-Americanism) I see from the prosecution and the European media with regards to Amanda Knox. I'm also appalled at how much rumor is reported as fact.

I consider myself to be highly familiar with both sides' arguments, but did as you suggested and also spent some time looking over both sites you recommended - my opinion did not change.

I'm pretty confident our opinions are shared.

Looking forward to your thoughts on this experiment of yours.

Comment author: Jack 10 December 2009 03:00:44AM *  2 points [-]

Great idea. I had heard the name Amanda Knox and knew that she was suspected in a murder of another exchange student in Italy. Thats it. I looked at both sites and much of the evidence. I glanced at the wikipedia page briefly and did a limited google search to try and find information about one more fact that I was hoping to find in the pro-Amanda page, but didn't.

My answers:

  1. 13% she was in the room and assisted in the murder. 9% She was involved in some other way, had prior knowledge etc..

  2. 15% in the room, 9% other involvement.

  3. 97%

  4. I'd say there is a 60% chance all your estimations are within 15 percentiles of mine.

A couple notes: The thing keeping 1 and 2 up there for me are the times on Knox's phone calls to Kercher. 3 and 4 seconds is way to short. But so much of the Kercher site appears to be unsubstantiated rumor I can't figure out if this was actually evidence or made up and unproven. I also can't figure out what Sollecito and Knox claimed to be doing during the time frame of the murder. They were obviously on drugs and then coerced into false statements so it is plausible they would be confused and have inconsistent stories but I don't know what they ended up claiming in court so I'm left with their statements to the police.

Also, I found that seeing the faces of the girls immediately undermined my objectivity. Not one way or another necessarily, but I felt emotional attachments to the case coming on at a disturbing rate. I would feel a lot better about my estimations if I hadn't seen their photos.

Finally, making this comment without seeing anyone else's estimations is definitely a little scary.

Update: I've gone over the timelines. Incredibly frustrating since I can't seem to find an objective account anywhere. But it doesn't look good for Knox and Sollecito. The short phone calls are really bothering me. I'm bumping up the probabilities they were involve by 25% each. Since I'm now in the middle I imagine I'm not that close komponisto's view. I'm gonna take a break since reading this stuff is making me really sick. But does anyone have an explanation for the phone calls?

Comment author: saliency 09 December 2009 10:40:36PM 2 points [-]

This was my first contact with this story. I still don't feel informed.

Wikipedia was the best of the resources. The site arguing defendants are guilty was the worst. My probabilities on Konx and Sollecito are "high" because I feel I still have not found an argument against them that was properly constructed. Before lowering my probability to 1% I would like to hear a better explanation of why the court found them guilty.

  1. Your probability estimate that Amanda Knox is guilty. p = 6%
  2. Your probability estimate that Raffaele Sollecito is guilty. p= 6%
  3. Your probability estimate that Rudy Guede is guilty. p = 70%
  4. How much you think your opinion will turn out to coincide with mine. p = 90% (That we both agree in direction; that RG is probably guilty. I expect your probabilities are higher though)

** Note that I leave plenty of probability for the possibility that none of the three are guilty.

Comment author: LauraABJ 09 December 2009 09:18:19PM 2 points [-]

1) Knox guilty = 0.2, however 0.35 that she discussed something seriously or not with Guede before the murder. 2) Sollecito = 0.05 3) Guede = .98 4) Your opinion is probably similar to mine. 5) The wikipedia article.

Comment author: Cyan 09 December 2009 06:53:07PM 2 points [-]

I was totally unfamiliar with the case. My assessment is based on ~30 minutes of reading the pro-prosecution site and ~5 minutes of reading the pro-defense site.

  1. My probability estimate that Amanda Knox is guilty: 33%.
  2. My probability estimate that Raffaele Sollecito is guilty: 33%.
  3. My probability estimate that Rudy Guédé is guilty: 90%.
  4. How much I think my opinion will turn out to coincide with yours: same direction, mine less extreme.

For me, the red flag was the way Guédé replaced Lumumba in the prosecution's theory of the crime. An investigation in which suspects are hot-swappable does not inspire confidence.

The reasoning on the pro-prosecution site did not impress, e.g., the fact that Knox did not participate in a program for exchange students at the University of Washington is taken as evidence speaking to her character, specifically, of her desire to be free of social constraints.

Comment author: tut 09 December 2009 08:59:51AM *  2 points [-]
  1. Your probability estimate that Amanda Knox is guilty.

5%. She was near the crime scene and doesn't have a coherent story about what she did that day. She might have bought bleach. Other than that they don't appear to have any evidence against her.

  1. Your probability estimate that Raffaele Sollecito is guilty.

5%

  1. Your probability estimate that Rudy Guede is guilty.

95%. Handprints in blood. His blood mixed with the victims. His "DNA" "inside" the victim. If he is not guilty then he was framed in a quite advanced manner. And in that case I'd expect him to have something to say about how they got his blood and handprints.

  1. How much you think your opinion will turn out to coincide with mine.

Probably quite similar.

Comment author: Daniel_Burfoot 09 December 2009 03:18:51PM *  3 points [-]
  • P(AK=guilty) = .01
  • P(RS=guilty) = .01
  • P(RG=guilty) = .995

Do I think my assessment will coincide with yours? Of course I do, we're supposed to be rationalists!

I had zero familiarity with the case before reading the links provided, and did not read any of the comments in reaching my estimate.

I admit to having non-trivially updated based on my perception of the lack of seriousness of the pro-conviction site's domain name (what is this, Marvel Comics?)

Comment author: ciphergoth 09 December 2009 08:05:06PM 3 points [-]

Those are very high confidences, could you say a little about that?

Comment author: Daniel_Burfoot 10 December 2009 03:41:50PM 7 points [-]

The prior probability of a three-way conspiracy to commit rape and murder is way, way lower than the prior probability of it being a one man job.

I didn't see any evidence that would move much probability mass away from the prior probabilities, but this could just be due to the slice of the evidence I saw given my 30 minutes or so of reviewing it.

Comment author: komponisto 09 December 2009 06:36:52PM 1 point [-]

I admit to having non-trivially updated based on my perception of the lack of seriousness of the pro-conviction site's domain name

How much of a shift do you think this accounted for? What would your estimates have been if the same site had been called something different?

Comment author: Daniel_Burfoot 10 December 2009 03:52:34PM 1 point [-]

How much of a shift do you think this accounted for? What would your estimates have been if the same site had been called something different?

The name is just one piece of evidence. Overall the pro-conviction site did not impress me at all. It seemed to be full of irrelevant statements, and things like site usage statistics.

Comment author: lordweiner27 10 December 2009 02:04:32AM *  2 points [-]

Amanda Knox being Guilty: 90%

Raffaele Sollecito being Guilty 90%

Rudy Guede being guilty: 90%

I hope you agree with me because no one else in the comments seem too. I'm gonna give the probability of you agreeing with me 75% based on my own arrogance and belief that I'm right and based and little else really.

Most people seem to believe Rudy Guede is guilty so lets skip that and look at the other two. They've changed their stories and have been proven to have lied quite a few times. For example Rudy at one point said he was at home surfing the internet but his alibi is not substantiated by records of his internet service provider.
Amanda at one point said she was round Rudy's house till 10am (later changing her story) but according to a witness she was at the store as soon as it opened to buy cleaning products.

That alone is some strong evidence that they are both guilty.

If they were innocent there would be no need to lie.

Probably the most damning piece of evidence is this:

When Sollecito's home was searched, a knife was found in a kitchen drawer that contained small traces of Kercher's DNA on the blade, and Knox's on the handle.

There really is no other explanation for that. Unless she was round Sollecito's home at some earlier date and cut herself on his knife.

Here's another nail in the coffin:

Sollecito's footprint was found in blood in Kercher's room.
Don't forget this was behind a locked door!

Add all that evidence to the cleaning up afterwards, the body being covered, the rape fantasies Knox had, Sollecito's DNA on her bra etc. etc. All three of them clearly killed her. The jury clearly believed so as well which strengthens my argument. They spent months examining the case, so the idea that a few minutes of internet research makes you certain they're wrong seems laughable.

Comment author: imaxwell 10 December 2009 06:18:52PM 7 points [-]

Do you really find it equally likely that Knox/Sollecito are guilty as you do that Guede is guilty? It seems like most of the weight should be given to Knox-Sollecito-Guede and Guede as possibilities, so unless you think the probability of Guede acting alone is very close to zero, this is sort of bizarre. In particular, it indicates that your P(KSG | G) is very close to 100%.

Comment author: Blueberry 11 December 2009 08:07:09AM 0 points [-]

Downvoted for poor spelling.

Comment author: Jack 10 December 2009 04:18:38AM *  1 point [-]
  1. The statements were obviously coerced and Knox and Sollecito were intoxicated during the period in question, it isn't surprising they have given inconsistent and contradictory stories.The fact that no recording of the interrogations was ever released is incredibly damning.

  2. My understanding from what I saw was that no evidence re: purchasing cleaning products was ever introduced.

  3. Did you read the arguments countering the DNA evidence?

Sollecito's footprint was found in blood in Kercher's room. Don't forget this was behind a locked door!

Was this luminaled or visible? I might have missed this piece of evidence. Also, I wasn't at all convinced there was any clean-up afterward.

Comment author: lordweiner27 10 December 2009 09:51:52AM 0 points [-]
  1. Just because they were intoxicated doesn't mean they shouldn't be able to tell us where they were. I have never been drunk enough in my entire life to not remember what house I slept at. Have you?

The fact that no recording of the interrogations was ever released is incredibly damning.

So because the police were idiots and didn't record the interrogations that means they faked the evidence? What would be the police's motivation for faking the evidence?

My understanding from what I saw was that no evidence re: purchasing cleaning products was ever introduced.

Evidence is held back for lots of reasons, doesn't didn't happen. It was on the wikipedia page so I'm taking it as fact.

  1. No. I'd love a link to them. However I can't invision reasonable argument against DNA evidence, unless there's evidence of a massive police conspiracy.
Comment author: Jack 10 December 2009 10:35:59AM *  3 points [-]

Just because they were intoxicated doesn't mean they shouldn't be able to tell us where they were. I have never been drunk enough in my entire life to not remember what house I slept at. Have you?

Intoxicated people as a rule have fuzzy and missing memories. I've definitely forgotten events when I've been drunk and I've had friends lose a couple hours of memory and wake up not knowing where they are. Maybe this isn't sufficient to explain the inconsistencies but it is once you combine it with scary, potentially abusive police yelling at and threatening them... well, I'd say some inaccurate testimony is to be expected.

That said I'm having trouble with their story of the morning the body was discovered.

So because the police were idiots and didn't record the interrogations that means they faked the evidence? What would be the police's motivation for faking the evidence?

Initially the police said they had lost the recording and later said they had never made one. In fact, they didn't even have a transcript of the the interrogation just a signed statement in flawless italian. These things "get lost" when the police realize the confession was coerced and won't hold up on appeal once people see the video tape. And are you really asking me why police would manufacture evidence to get a conviction? Like, are you kidding? If you want a motive unique to this case you might read the criticism of the Italian prosecutor. From the wikipedia page:

Mignini is currently under investigation for pursuit of bizarre and lurid psycho-sexual homicide theories in another Italian murder investigation, regarding a serial killer dubbed "The Monster of Florence." Criticism of Mignini's methods, accusations of mental instability and fascination with the occult have dogged him in the media and a senior Florentine minister has gone on the record stating his opinion that Mr Mignini had fallen "prey to a sort of delirium".

Evidence is held back for lots of reasons, doesn't didn't happen. It was on the wikipedia page so I'm taking it as fact.

It doesn't mean it didn't happen. It may have, I'm not convinced of their innocence. But the fact that it is on a contested wikipedia article is a terrible reason to take it as fact. Wikipedia is great for reading about the history of cheddar cheese, less so for answering questions about current, controversial and biasing events. Btw, did you really read the defense's site? Quoting:

Early in the trial, the prosecutor seemed to be aware that the washing machine was a matter of interest to people discussing the case on the Internet, because he made a point of asking several witnesses about it. But nothing of value emerged from these questions. Insiders have known for a long time that the police examined the contents of the washing machine and found nothing incriminating.

Finally:

However I can't invision reasonable argument against DNA evidence, unless there's evidence of a massive police conspiracy.

This was in the main section of the defense's site. Section 2.

Comment author: zero_call 09 December 2009 06:49:04AM 2 points [-]

Maybe this is a bit unsportsmanlike of me, but, for the question: "What probability your own opinion is accurate", my answer would be.... low enough to preclude me from participating in the other predictions.

Comment author: MerleRideout 01 January 2011 05:30:57PM 1 point [-]

I'm pretty familiar with this case having read a couple of books about it and followed both of the websites listed and a few others.

I would say there is 0 chance of Knox or Sollecito being involved in the murder at all. They have no motive. The prosecution completely failed to show that they had ever participated in "sex games" together or with different partners in the past. There is no evidence of either of them at the crime scene at the time of the crime. None of their past behaviors make them likely candidates to commit this type of crime. Even the circumstantial evidence Judge Massei used to convict them is stretched and convoluted: that Knox bathed twice in 24 hours, that they turned their cell phone off together apparently before going to bed and on again together when they got up briefly early in the morning, that Sollecito didn't use his computer for a few hours. There are many many reasons besides taking part in a homicide by which these behaviors might occur. I doubt that these two people are in any way involved with the crime.

Rudy Guede I'd say 60% he's probably guilty of the murder. All the physical evidence, bloody hand print, bloody foot prints, mitochondrial DNA in the victim, in the victim's purse, belong to Rudy Guede. He was certainly at the crime scene. He certainly had some kind of interaction with Meredith Kercher that night. He has exactly the type of criminal profile that would lead him into this sort of circumstance. He is probably the murderer.

The thing that gives me pause is Guede's persistent denial that he murdered Kercher. This guy is a smash and grab burglar. He does not think ahead. He does not plan his escapes. He does not enter the crime scene thoughtfully with the idea of maximum profit. All his crimes are crimes of desperation, crudely executed. I doubt he meant to murder Meredith Kercher. He was there to rob. Rape presented itself to him as an opportunity. He attempted it. She resisted. He murdered her accidentally. With criminals of this type you would expect the perpetrator to be remorseful and confess. They nearly always do. Rudy does not. That bothers me.

If we believe Rudy, however, we enter the next realm of probability. Could Meredith Kercher be unlucky enough to be burglarized by Guede and then have a couple of other bandit murderers stop by , too? Doesn't seem likely to me. Was she MI5 or dealing drugs, herself? Did anybody check? I'm not happy with it.

I suspect you'll agree with me within 20%. There are no scientists or law enforcement officials outside of Italy that give any credence to the prosecution's analysis of this crime. As of yesterday, even the Italian government is backing away from these police and prosecutors. Knox and Sollecito will be freed on the review of the DNA analysis. Knox will be given time served on her so-called "slander" charge and they'll send her home to Washington state before her 24th birthday in July.

Comment author: JoshuaZ 01 January 2011 06:09:05PM 3 points [-]

I would say there is 0 chance of Knox or Sollecito being involved in the murder at all.

Assigning probability zero to something is not in general a good idea.

Comment author: bogdanb 10 December 2009 05:53:46AM *  1 point [-]

Context: I didn't know anything about the case; I think I've overheard something about it in the past, because I had a very slight sensation of déjà-vu reading your post, but I didn't really know anything. The info I used was reading the Wikipedia pages (one you linked and one on one of the trials), then skimming the sites you linked for less than a half hour.

I have reached a “decision” about it, but I didn't intend to post it. Then curiosity got the best of me and I read pretty much all the comments already here. My “estimate” wobbled a bit during the reading of the comments, but by the end it converged on its initial value. I decided to post my opinion, as somebody else mentioned, to avoid self-selection.

I used quotes above because my general state is confusion. Actually, it's confusion both about the case and about the poster's opinions (and, a bit, about your post).

The general impression I got was that all parties (except, probably, the victim) are guilty of something, including the prosecutors. But...

First, I'm not very sure exactly if your questions should be translated as “probability estimate that X killed Kercher” or not. I actually have a slight suspicion that your post might be a trick question around that. (In fact, writing now, I realize that the trial resulted in guilty verdicts on ~five counts for each, but after all the reading I have no idea what they are other than that one of each is some kind of murder.)

Regarding Knox and Sollecito, my “gut” impression is that they're guilty of something, in the sense that I'd be quite surprised if they were just two innocent people who did absolutely nothing bad (other than that joint) and got dragged in a nightmare by chance. I also have a “gut” feeling that their “guilt” is correlated.

Regarding Guede, I've got a slightly stronger gut feeling of guilt (than I do for the first two).

I also feel (as in “gut”, again) that the prosecution and trial was “wrong”. (EDIT for clarification: but I can't see any basis of estimating how wrong between “as good as reasonably possible” and “gross miscarriage of justice”.)

However, what confuses me most is the certainty of most estimates I've seen in the comments. I just don't see how one can get much farther than “I don't know, but I lean a bit towards” either way on what the posters report as their information. I mean, after only a couple hours or so of thinking (both during reading and writing this) I'm not even sure what priors might be appropriate. I feel I know so little about the case (including info like trials in general) that my response can't be more than “I don't know”. (If pressed a lot I'd output 0.5±e as a probability, simply because even my knowledge of probabilities is too weak to actually figure out if anything else would express my almost total uncertainty on this subject, and that's my cached answer for binary questions.)

Put differently, given the information I have on the subject, it feels as if the confidence I should assign to any probability estimate should be very close to 0. As I said above, I tend to give probabilities as ~50% in those cases, but that's not exactly a correct description of what I feel. A good description would be that, if forced to bet (without more time to think), I'd bet on all of them being guilty, but if given the option, I wouldn't bet any amount at 1:1 odds.

Oh, and the answer to the fourth question is very similar. Leaving aside the fact that I'm not sure exactly how I'd quantify the “coincidence” of opinions, I'm wouldn't put any significant confidence in any estimate. (The “gut” feeling is that you consider all three guilty, but that's mostly a very vague impression I got from the wording of your text rather than reasoning on my part.)


As an aside, the interesting thing about the subject is that I was surprised how little confidence I assigned to my “estimates” in this case. I usually have some opinion on most questions I encounter, but in this case I find myself really unable to arrive at one.

Comment author: komponisto 10 December 2009 06:20:41AM *  0 points [-]

First, I'm not very sure exactly if your questions should be translated as “probability estimate that X killed Kercher” or not. I actually have a slight suspicion that your post might be a trick question around that

No, "X killed Kercher" is right. (Or perhaps better would be, "X participated in killing of Kercher".)

Comment author: dilaudid 10 December 2009 02:28:39AM *  1 point [-]

I've looked at this twice - first after reading the friends of amanda blog, wikipedia, and scanning the justice for meredith blog.

My initial probabilities were: P(AK=guilty) = .55, P(RS=guilty)=.5, P(RG=guilty)=.999, P(views coincide)=.5. Having read a few comments I initially revised the first two probabilities down - I realised I was guilty of having given a lot of weight to the rape story, and not given weight to the improbability of the "weird sex" story.

Having read more I find it hard to be sure of anything - it seems to be next to impossible to get any unbiased information on this (wikipedia contradicts friends of amanda, e.g. on the washing machine and the cleaning operation which are crucial). I would also be astonished if the Italian legal system could encourage such a high-profile miscarriage to take place. Italy is one of the most developed countries in the world. While they do have a mad president, some might say the same about some American presidents. And I have seen clear one-sided bias against the Italian legal system (e.g. the sashes worn by the jury - standard dress for jurists in Italy)

EDIT: Looked at this again. I've got to revise them to .99, .99, .999, .9 Some excerpts from the evidence on this blog - the evidence that FoA discounts looks very real to me. The only thing I find really weird is how the three could have got together. http://boards.insessiontrials.com/showpost.php?p=13695224&postcount=718

Comment author: gwern 10 December 2009 10:43:02PM 2 points [-]

And I have seen clear one-sided bias against the Italian legal system

Keep in mind, this bias may not be entirely unjustified. The guilty blog quotes a major Italian newspaper (it says) which itself jokes about the Italian's system 'near biblical' slowness and forthrightly admits that it is the target of much legitimate criticism. And then there's the general black market economy of Italy, tax evasion, and dispect for the law. The Maxi Trial is an interesting example, without so far as I know, any American analogue:

"The existence and crimes of the Mafia had been denied or merely downplayed by many people in authority for decades, despite proof of its criminal activities dating back to the 19th century. This can be attributed in part to three particular methods used by the Mafia to provide an environment akin to near immunity - paying off key people, killing real or perceived leaks in their own organization, and threatening or even killing key people (judges, lawyers, witnesses, politicians...) were used successfully to keep many prosecution efforts at bay. In fact it was only in 1980 that it was first seriously suggested that being a member of the Mafia should be a specific criminal offence by Communist politician Pio La Torre. The law only came into effect two years later - after La Torre had been gunned down for making that very suggestion.

After Chinnici’s murder in July 1983, his successor Antonino Caponnetto, headed the pool. The Antimafia pool was a group of investigating magistrates who closely worked together sharing information on related cases to diffuse responsibility and to prevent one person from becoming the sole institutional memory and solitary target. [Shades of Death Note!]

The Maxi trial took place next to the Ucciardone (the Palermo prison) in a bunker specially designed and built to try the defendants. It was a large octagonal building made from reinforced concrete that was able to prevent rocket attacks; inside there were cages built into the green walls holding the many defendants in large groups. There were over six-hundred members of the press as well as many carabinieri wielding machine guns and a 24-hour air defense system keeping an eye on the defendants and would-be attackers attempting to thwart the efforts.

There were many critics of the Maxi Trial. Some implied that the defendants were being victimized as part of some sort of vendetta of the magistrates. The Sicilian writer Leonardo Sciascia said that: "There is nothing better for getting ahead in the magistracy than taking part in Mafia trials." Cardinal Pappalardo of the Catholic Church gave a controversial interview where he said that the Maxi Trial was "an oppressive show" and stated that abortion killed more people than the Mafia.

The Maxi Trial was largely regarded as a success. However, the appeals process soon began, which resulted in a shocking number of successful appeals on minor technicalities. Most of this was thanks to Corrado Carnevale, a judge in the pay of the Mafia who was handed control over most of the appeals by the corrupt politician Salvatore Lima.

In January 1992, Falcone and Borsellino managed to take charge of further Maxi Trial appeals. Not only did they turn many appeals down, they reversed previous successful ones, resulting in many Mafiosi who had recently swaggered out of prison after their convictions were overturned being unceremoniously rounded up and put back behind bars, in many cases for the rest of their lives....That summer, Falcone and Borsellino were murdered in audacious bomb attacks."

(My apologies for the lengthy quoting, but does this sound like a peaceful highly law-abiding nation, with an effective and uncorrupt judicature?)

Comment author: jkaufman 27 September 2011 08:29:04PM 1 point [-]

Those are very high probabilities.

Comment author: telms 11 August 2013 05:36:49AM *  1 point [-]

Guesstimates based on quick reading without serious analysis:

(1) Probability that Amnda Knox is guilty: 5%

(2) Probablility that Raffaele Sollecito is guilty: 10%

(3) Probability that Gudy Guede is guilty: 60%

(4) Probability that my estimates are congruent with OP's: 50% (ie random, I can't tell what his opinion is)

Comment author: John_Maxwell_IV 15 December 2009 04:59:11AM 1 point [-]

Very little familiarity prior to this post, read both sites for maybe 5 minutes each.

  1. 50%
  2. 40%
  3. 90%
  4. Your username looks vaguely Italian, so I'm guessing that your estimates of the chances that Knox and Sollecito are guilty is significantly higher.
Comment author: komponisto 15 December 2009 05:26:44AM 3 points [-]

Your username looks vaguely Italian, so I'm guessing that your estimates of the chances that Knox and Sollecito are guilty is significantly higher.

My username is Esperanto for "composer"; you wouldn't find the letter "k" in a native Italian word.

As for what my own estimates are, see here.

Comment author: pete22 11 December 2009 07:07:11PM 1 point [-]

I have a different objection to the premise: the presumption of innocence in modern legal systems means that the job of the jury (and by extension the legal teams) is not just to arrive at a probability of guilt but at a certain level of confidence around that probability.

I realize that these can technically be made equivalent by endless "priors" -- i.e. a juror walks into the courtroom with a certain set of beliefs, ie probability .8 that someone on trial is guilty, .01 that a sex crime would have been committed by a female rather than a male, etc etc etc, and mentally revises them according to every input -- but in any normal intuitive sense the job of a juror is not to answer the exact questions you've presented, but to judge the strength of the prosecution's case from a skeptical viewpoint.

So when you conflate the process/outcome of the trial with an independent, rational probability estimate, I think you make it hard for anyone to give you an impartial answer. And this starts right in the title with "you be the juror" -- but it extends all the way to minor points like the use of the term "guilty" which has both legal and colloquial meanings.

Comment author: mattnewport 11 December 2009 07:15:58PM *  2 points [-]

the presumption of innocence in modern legal systems means that the job of the jury (and by extension the legal teams) is not just to arrive at a probability of guilt but at a certain level of confidence around that probability.

I don't think those are two separate things. What does it mean to be 50% sure that there is a 90% probability someone committed the murder? If you're not sure you should just lower your probability of guilt.

I think Eliezer had it right that when answering the question you should give your best estimate of the probability that each suspect committed the murder. The question of what probability corresponds to 'beyond reasonable doubt' is a separate one and isn't actually raised in the original question. Personally I think you'd have to assign at least a 90% probability of guilt to convict but the exact threshold is open to debate.

Comment author: pete22 11 December 2009 08:49:32PM *  2 points [-]

I just went to Wikipedia and found a more articulate version of what I'm trying to say:

Gardner-Medwin argues that the criterion on which a verdict in a criminal trial should be based is not the probability of guilt, but rather the probability of the evidence, given that the defendant is innocent (akin to a frequentist p-value). He argues that if the posterior probability of guilt is to be computed by Bayes' theorem, the prior probability of guilt must be known. This will depend on the incidence of the crime, which is an unusual piece of evidence to consider in a criminal trial. Consider the following three propositions:

A: The known facts and testimony could have arisen if the defendant is guilty,

B: The known facts and testimony could have arisen if the defendant is innocent,

C: The defendant is guilty.

Gardner-Medwin argues that the jury should believe both A and not-B in order to convict. A and not-B implies the truth of C, but the reverse is not true. It is possible that B and C are both true, but in this case he argues that a jury should acquit, even though they know that they will be letting some guilty people go free. See also Lindley's paradox.

I am not really a stats person and I'm not prepared to defend Garder-Medwin's model as being correct -- but right or wrong, it's a better description than Bayesian inference of most people's intuitive concept of the task of a juror.

In other words, when I imagine myself as a juror I'm automatically more concerned about a false positive (convicting an innocent person), and I will intuitively try to answer the question "has the prosecution proved its case" rather than "is this person guilty."

If asked to answer the second question and quantify my odds of guilt, I'm likely to understate them, precisely because I can't separate that estimate from the real-world effect of a guilty verdict.

Or in your terms, the "question of what probability corresponds to 'beyond reasonable doubt' [or whatever the equivalent standard in Italy]" can't be completely excluded from the question when we imagine ourselves as jurors, only made implicit.

This reminds me slightly of Eliezer's "true Prisoner's Dilemma" article, which I really liked. Just as you can't posit that someone is my confederate (in his case) and then ask me to consider them in a purely selfish, impartial way -- you can't tell me I'm a juror and then ask me to make a purely impartial assessment. I'm describing a much weaker effect than he was, and maybe it's more socially conditioned than inherent to human nature, but I think the general concept is the same.

So ...better to say "forget the fact that there's even a trial going on, just imagine that tomorrow the absolute truth will be revealed and you have to bet on it now."

Comment author: mattnewport 11 December 2009 09:21:03PM *  1 point [-]

He argues that if the posterior probability of guilt is to be computed by Bayes' theorem, the prior probability of guilt must be known. This will depend on the incidence of the crime, which is an unusual piece of evidence to consider in a criminal trial.

This is an interesting point and one where I think the legal system is wrong from a strict rationality sense but I can see the argument given that juries are human and so not very rational.

It is common for juries to either not be given information which is very relevant to the prior probabilities of guilt or instructed to discard it. The debate in the UK over whether previous convictions should be admissible as evidence is a good example. From a strict Bayesian/rationality point of view, all information is potentially relevant and more information should only improve the decisions made by the jury.

Information about previous convictions is very relevant when determining priors for certain types of crimes, particularly sexual offences which triggered calls for changes to the law in the UK. The counter argument is that telling juries about prior offences will bias them too much against the defendant, in recognition of the fact that juries are prone to certain kinds of irrational bias.

The rules about keeping juries away from potentially prejudicial media coverage exist for similar reasons. The failure to avoid this in the Amanda Knox case is one of the criticisms leveled against the prosecution by her supporters.

Comment author: DanArmak 12 December 2009 12:20:37AM 0 points [-]

From a strict Bayesian/rationality point of view, all information is potentially relevant and more information should only improve the decisions made by the jury.

From a really strict Bayesian point of view, more information can certainly make decision worse. Only perfect information (or, perhaps, arbitrarily close-to-perfect information??) necessarily makes decisions better. Of course, perfect information includes the bit of information saying whodunnit.

Here's another way to put it. Given a jury, you (the court) can give them information that will cause them to decide guilty, or you can give them other information that will cause them to decide not guilty. In many cases both sets of information will be true - just different subsets of the complete truth. How do you decide what to tell them?

Comment author: mattnewport 12 December 2009 12:42:58AM 0 points [-]

From a really strict Bayesian point of view, more information can certainly make decision worse. Only perfect information (or, perhaps, arbitrarily close-to-perfect information??) necessarily makes decisions better.

Not true. A perfect Bayesian updater will never make worse decisions in the light of new information. If new information causes worse decisions that is a reflection that the new information was not appropriately weighted according to the trustworthiness of the information source.

In other words, false information can only make for worse decisions if it is treated as true. The only reason you would treat false information as true is that you placed too much trust in the source of the information. The problem is not the receipt of the new information, it is incorrect updating due to incorrect priors regarding the reliability of the information source. That may be a common problem for actual imperfect humans but it is not an indication that acquiring new information can ever lead to worse decisions for a theoretical perfect Bayesian updater.

Comment author: TruePath 25 October 2012 07:22:46AM 0 points [-]

That's not quite right. The provision of all true but biased information (e.g. only those facts that are consistent with guilt) without complete awareness of the exact nature of the bias applied can increase the chances of an error.

Even unbiased info can't be said to always help. A good example is someone who has crazy priors. Suppose someone has the crazy prior that with probability .99999 creationism is true. If they have somehow aquired evidence that overcomes this prior but further information about problems with evolutionary theories would leave them with still strong but not convincing evidence that evolution is true then providing them with that evidence increases their chance of error.

More generally, disagreement in priors forces one to believe that others will make better decisions if evidence that exacerbates the errors in their priors is provided.

Comment author: DanArmak 12 December 2009 12:52:57AM *  0 points [-]

Additionally to my first reply, even if all the data the updater is given is completely true, incomplete data can still lead to worse decisions. Here's a trivial example.

This is a list of true facts (not really, just in the example): (1) B was murdered. (2) A was in town on the day of the murder. (3) A is green. Green people are less likely to commit murder than the general population. (4) A was B's close friend. Most murders are commited by friends.

A perfect Bayesian judge is asked: given fact (1), did A murder B? He has some prior probability for this. Then he is given fact 2. His probability (of A's guilt) goes up. Then he is given fact 3; the probability goes down. Then fact 4; it goes up again. And so on. This works independently of whether A murdered B or not.

Comment author: mattnewport 12 December 2009 01:08:49AM 0 points [-]

I think you're confusing two things here: a) is the judge making the best decision in light of the information available to him and b) in light of new information is his probability moving in the 'correct' direction given what really happened. The question of b) is irrelevant: the best we can hope for is the judge to make the best possible decision given the available information. A perfect Bayesian judge will do that.

The problem in the real world of humans is not whether giving them new information will lead them closer to or further from 'the truth' but whether they will update correctly in light of the new information. The reason certain facts are withheld from juries is that it is believed they will not update correctly on the new information but rather will be consistently biased in a particular direction by it to an extent not warranted by the facts.

Comment author: DanArmak 12 December 2009 01:19:20AM 1 point [-]

I think you're confusing two things here: a) is the judge making the best decision in light of the information available to him and b) in light of new information is his probability moving in the 'correct' direction given what really happened. The question of b) is irrelevant: the best we can hope for is the judge to make the best possible decision given the available information. A perfect Bayesian judge will do that.

That's right.

The reason certain facts are withheld from juries is that it is believed they will not update correctly on the new information but rather will be consistently biased in a particular direction by it to an extent not warranted by the facts.

That's not right. Even if the juries always update correctly on the new information they may still become more distant from the truth. The jury may be performing your (a) perfectly, but we do really want (b). My point was that even with a perfect Bayesian jury, the disrepancy between executing (a) and (b) will cause us to withhold certain facts sometimes, because the partial presentation of the facts will cause the jury's (a) to be closer to the actual (b), the truth.

Comment author: mattnewport 12 December 2009 01:27:47AM 0 points [-]

The jury may be performing your (a) perfectly, but we do really want (b).

We might really want to ride a unicorn as well but it's not really an option. Well, at least riding a unicorn is logically possible I suppose, unlike making decisions better than the best possible given the information available... The only way to get closer to the truth when you already update perfectly is to seek out more information.

The legal system is not designed around perfect updaters for the same reason it's not designed around unicorns. We wouldn't need judges and juries if we had perfect Bayesian updaters - we could just make those updaters investigator, judge, jury and executioner and tell them to deliver punishment when they reached a certain threshold level of probability.

The idea of withholding certain information from jurors is predicated on the idea that jurors are less good updaters than judges. Whether that is true or not is another question.

Comment author: DanArmak 12 December 2009 12:46:30AM 0 points [-]

The updater may be perfect, but because the updater's knowledge is imperfect, the updater cannot correctly judge the reliability of the source of information, and therefore it may assign that information incorrect (imprecise) weight or even take false information for true.

Comment author: mattnewport 12 December 2009 12:56:07AM 0 points [-]

We're talking about a hypothetical perfect updater that always updates correctly on new information. If it's updating incorrectly on new information due to putting too much trust in it given it's current state of knowledge then it's not a perfect updater.

Comment author: DanArmak 12 December 2009 01:01:15AM 0 points [-]

What you call a perfect updater here is an agent with perfectly complete knowledge. That's the only way to always judge correctly the weight of new information. Of course, such an agent never needs to update, at least not about past events.

Comment author: mattnewport 12 December 2009 01:14:35AM *  0 points [-]

No, I'm not talking about an agent with perfect knowledge. I'm talking about a perfect updater. A perfect Bayesian updater comes to the best possible decisions given the available information. Giving such a perfect updater new information never makes it's decisions worse because by definition it always makes the best possible decision given the information. This is a different question from whether it's probability estimates move closer or further from 'the truth' as judged from some external perspective where more information is available.

The concern with imperfect updaters like humans is that giving them more information leads them further away from the theoretical best decision given the information available to them, not that it leads them further away from 'the truth'. In other words, giving people more information can lead them to make worse decisions (less like the decisions of a perfect Bayesian updater) which may or may not mean their opinions become more aligned with the truth.

Comment author: gwern 10 December 2009 10:27:09PM 1 point [-]
  1. ~40%
  2. ~20%
  3. ~60%
  4. I think with reasonably high confidence that you will be on the 'K/S are innocent, and G guilty'; perhaps 70% confidence

My sources are occasional articles in the NY Times, a few other mainstream media by way of Reddit, and 30 minutes of reading through the 2 linked sites. The blog one seemed very bad to me; I gave up reading it in disgust about halfway through the post on the telephone chronology, because I was tired of the breathless insinuations that if someone has a detailed phone-call, obviously they must remember it flawlessly hours or weeks later even despite an incredibly number of events & conversations in between, and any claim to the contrary is just a cover-up. I wasn't surprised to see the pro-Knox website mention that the one-fingerprint was not significant according to the fingerprint expert witness.

(This makes sense to me - if Knox were industriously cleaning up the entire cottage, how could she miss a glass cup? I mean, you can actually see fingerprints on glass cups, so I don't how she could very competently clean up all the hidden and obscure fingerprints that there was insinuated to exist and then have a sudden fit of utter incompetence with the dishes.)

My original opinion was roughly 50%, moving to 60% when I heard of the conviction, but if the anti-Knox's case is that bad... And I have difficulty with the explanations of why Guede would kill Knox in conjunction with 2 others.

(And now to look at what everyone else wrote!)

Comment author: magfrump 10 December 2009 09:16:13PM 1 point [-]

I ended up spending a lot of time looking over the two provided sites, without having ever heard of the case before.

The parts of the "true justice" site that I found most helpful were:

http://truejustice.org/ee/index.php?/tjmk/comments/how_the_media_should_approach_the_case_if_justice_is_to_be_done_and_seen_to/

http://www.truejustice.org/ee/index.php?/tjmk/comments/why_defendants_mostly_dont_testify_those_devils_that_lurk_in_the_details/

Whereas the FoA site seemed very well put together.

The primary pieces of evidence that shape my current beliefs (I have admittedly looked through the comments but they've become heterogeneous enough that I don't think they've effected me too much) are:

The FoA site provides a clear outline of possible events, and addresses every outlier I have seen presented. This outline involves the least amount of criminal activity, and so has the highest prior probability for me.

The True Justice site provides a clear outline of possible events, but these events seem to be in contradiction with the FoA events. Specifically, a major point of evidence is the "cleanup phase" which FoA points out was not used by the prosecution--I do not consider the existence of the "cleanup" to be in evidence. The page also involves more conspiracy, giving it a lower prior probability for me.

TJ claims Amanda's confusion about phone calls made is evidence--to me it seems like evidence of her innocence. I would expect an innocent person to be more confused and forgetful than a guilty one. I would expect a guilty person who was covering up to be more aware of content-unrelated details (such as the prosecution's assertion that a call was made at 3am seattle time).

FoA presents specific details about poor police protocol around the crime scene, as well as questioning the use of luminol and citing the prosecution's expert witness. TJ takes "bloody footprints" to be in evidence, I do not believe that they are.

Were I a jurist involved with the trial and were the evidence from these sites all that was presented to me, I would certainly rule that Amanda Knox was innocent, I do not feel that there is sufficient evidence to claim otherwise and cannot comprehend how someone would.

HOWEVER I noticed that 6 Italian judges had considered the case, that she was convicted by a jury, and that Judge Micheli produced a 106 page report on the guilt of RG which indicted RS and AK.

The prosecution has been noted as somewhat crazy, this makes the possibility that the jury wanted to signal disapproval of murder-rape at a level much higher than protect innocent people more probable.

TJ notes that RS and AK stood outside the girls' house the night of November 1. FoA claims that this was unreliable witness testimony.

I therefore believe that there is substantial evidence for the prosecution of which I am unaware, enough to convince 6 judges and a jury, much of which should be in the micheli report which there's no way I will read (106 pages of italian?!)

My beliefs hinge primarily on the believability of the testimony--were RS and AK at the house the night of 11/1, or did AK return the morning of 11/2?

Now, to answer the first four questions:

  1. P(AK guilty): 41% P(AK|at scene night of 11/1): 80% P(AK|not at scene): 2%

  2. P(RS guilty): 38% P(RS|at scene): 75% P(RS|not at scene): .5%

  3. P(RG guilty): 99% P(crazy shit): 1% P(RG guilty| no crazy shit): 99.9999%

  4. Since OP has claim to extra information concerning the case, I suspect that OP will be within 20% of my conditional beliefs for 1. and 2. with 70% confidence. Similarly I suspect that my aggregate beliefs (because they are split evenly between "intense anti-murderape-signaling" and "murderape conspiracy") for 1. and 2. will be FURTHER than 20% from OPs beliefs with 80% confidence.

Everyone on both sites and here seems convinced of RG's guilt. I think there's approximately a 1% chance of some crazy shit happening but otherwise this belief is primarily uninvestigated (relies mainly on people not writing 106 page reports about innocent people murdering each other).

Comment author: GreenRoot 10 December 2009 08:05:41PM 1 point [-]

For those of you who were not familiar with the case, which side's arguments did you read first?

Did it feel like this order influenced your reasoning or final judgment?

(I read pro-guilt ideas first, and feel now that this ordering contributed to my judgment that Knox and Sollecito are guilty. I wonder how conviction rates would change in the US if we let the defense go first, i.e. what are the relative influence values of the right to speak first vs. last?)

Comment author: ChristianKl 12 December 2009 08:53:34PM 2 points [-]

The principled position is to read the arguments in favor of non-guilt first because we generally believe in the presumptions of innocence and therefore should set up our minds with a bias to innocence rather than a bias to guilt when you have to have a bias but can't control it.

Comment author: loqi 10 December 2009 10:39:25PM 1 point [-]

I flipped a coin, and it landed "read pro-guilt first". My take on its effect is basically the same as Cyan's.

Comment author: JamesAndrix 10 December 2009 10:36:29PM 1 point [-]

I read 'friends of amanda' first, and was definite biased towards her innocence and guede's guilt for much of the rest of my reading. I didn't find anything particularly compelling against knox. The last thing I looked at was the wikipedia article, which knocked down my confidence in guede's guilt a lot. Overall, I think I compensated for the first impression I got.

I'm not so sure I compensated for the fact that the pro-guilt site was stupidly 'think of the poor murdered victim, there has to be justice, and by justice we mean guilty verdicts.' The pro innocence side definitely struck me as more rational.

Comment author: Jawaka 13 December 2009 02:37:06AM 0 points [-]

This.

I was thoroughly annoyed by the sites layout and structure. If your main focus is on pictures of the victim and youtube videos, you don't really have a lot of arguments.

Friends of Amanda looks a lot more professional and the main points are much more condensed.

Estimates at three at night, very tired but sober. First tried to read the pro- and contra-sites, but I was too confused by the layouts and didn't know where to start. Then went on reading WP article and was pretty sure about Guede being the sole perpetrator. Read the other sites again and found the guilty-side very unconvincing, the not-guilty-side much better. The not-guilty-side reminded me specifically of the holocaust deniers tactics which I know very well.

Couldn't force myself to read for longer than 30 minutes in total because I am very tired, might read something tomorrow but not expecting to change my opinion at all.

Knox guilty: 25% Raffaele: 25% Guede: 75% Agreement: 60%

After reading the comments, my estimates changed to 10/10/90

I hope this case goes to a European court or something. It really is a shame.

Comment author: Cyan 10 December 2009 08:45:31PM 1 point [-]

I read the pro-guilt side first. Whatever order effect there might have been was more than counteracted by the amount of crap I read through before getting to the actual evidence presented by the prosecution.

Comment author: AnlamK 10 December 2009 09:01:28AM 1 point [-]

Hello,

I haven't made up my mind yet - and if anyone's interested, this cbs take on it looks well done:

http://www.cbsnews.com/video/watch/?id=5915082n

Comment author: kip1981 09 December 2009 10:13:05PM 1 point [-]

By guilty, do we mean "committed or significantly contributed to the murder"?

Or do we mean "committed or significantly contributed to the murder AND there is enough evidence showing that to satisfy the beyond-a-reasonable-doubt (or Italian equivalent) standard of proof for murder"?

The comments don't seem to make that distinction, but I think it could make a big difference.

Comment author: Eliezer_Yudkowsky 09 December 2009 11:37:04PM 3 points [-]

probability = probability of having committed murder, not probability of sufficient evidence

Comment author: curious 09 December 2009 09:28:30PM *  1 point [-]

ak guilty: 0.1

rs guilty: 0.1

rg guilty: 0.9

assessment of my opinion vs poster's opinion: can't guess at your actual probabilities, but probability similar general take identifying guede as vastly more likely to be guilty than the other two.

sources: small number (i estimate <5) of media stories covering the case that i've seen over recent months plus the wikipedia article as it read at a little after 4 pm today.

Comment author: Morendil 09 December 2009 08:02:17PM 1 point [-]

I spent less than an hour browsing the two links provided and randomly surfing elsewhere afterwards. I was unfamiliar with the case before.

My estimated odds of Raffaele Sollecito being guilty of murder are very roughly 1:1, of Amanda Knox being guilty of murder a little less, of Ruedy Guede being guilty closer to 4:1.

Unfortunately I couldn't entirely avoid having a peek at comments before coming to an estimate - there were some numbers in the right-hand "recent comments" box of the site.

The main driver in my estimates is that all three were convicted. This implies that dozens of people, including a carefully selected jury, spent days poring over all available evidence and came to that conclusion "beyond reasonable doubt", and my own effort in assessing the evidence is necessarily shoddy compared to that.

I started out with about 4:1 to 9:1 confidence in their guilt, given the information provided in the post, which mentioned their conviction.

Then I started reading the Friends of Amanda site, reasoning that evidence mentioned as uncontroversial in a site arguing for the convicted would tend to be solid.

I browsed TJMK for a while as well, my take-away being that the principal question seems to have been whether one person (RG) or several were involved in the killing. I heavily discounted what I'd read there after I came across an article arguing against Amanda Knox on the basis of her liking singer Feist because Feist has published sexy pics.

On balance the evidence against Rudy Guede seemed rather damning, that against the other two much thinner. (Nobody seems to take seriously the idea that there could be something to RG's version of the facts.)

My peek at the comments here might have moved me slightly away from assuming the guilt of the two, perhaps as much as from .6 to .5 probability of guilt.

I suspect, if you think of this as a "rationality litmus test" (I don't, since the odds seem slim that we'll ever get to the bottom of the case, fact-wise), that you have formed an opinion that the two are not guilty.

Comment author: komponisto 10 December 2009 01:51:38AM 5 points [-]

including a carefully selected jury

Italy does not have voir-dire (juror screening) as in the U.S.

Comment author: gwern 10 December 2009 10:54:35PM 1 point [-]

Are they chosen by simple sortition? (randomly)

Comment author: jimmy 09 December 2009 07:20:05PM 1 point [-]
  1. p = 0.5
  2. p = 0.5
  3. p = 0.95
  4. I have pretty high confidence (~95%) that you got the right answer, which doesn't tell me which side you're on for the first two, but means you'll likely agree on the third.

As a disclaimer, I did peek at other peoples comments before writing these down, but I had mentally committed to these numbers before doing so. I had heard of the case a while ago though I never looked into it. I had the impression that Knoxx and Sollecito were guilty (based solely on the fact that they tend to get the right bad guys) and didn't remember hearing about a third person.

I just briefly skimmed the wiki page and the "innocent" site.

The evidence for the guilt of the first two didn't seem very strong, but I'm not familiar enough with forensics to know how much would be expected. There were some things against them (they were found guilty) but I'm gonna have to claim ignorance.

The evidence against Guede was pretty strong. I'm just not comfortable putting numbers higher than 95% because there's a number of unrelated ways that errors can build up.

Comment author: mattnewport 09 December 2009 07:45:06PM 4 points [-]

I don't mean to single you out particularly but your probabilities show a pattern common to several other commenters that I find surprising. What is your prior probability that a rape-murder would be committed by three people, a man and a woman who had been dating for a couple of weeks and a third man who was a stranger to both of them, rather than by a single man acting alone?

My prior probability for three people acting together like this would be extremely low. The fact that Knox and Sollecito had only been dating for a couple of weeks doesn't seem to be in dispute, nor does the fact that they did not previously associate with Guede. I'm surprised that people don't revise down their probability of Knox and Sollecito being guilty significantly if they believe Guede is guilty.

Comment author: ciphergoth 09 December 2009 08:07:10PM 2 points [-]

The fact that they were convicted is also evidence, of course.

Comment author: komponisto 10 December 2009 01:07:52AM 0 points [-]

How strong a piece of evidence do you think it is?

Comment author: jimmy 10 December 2009 01:27:39AM 1 point [-]

Before or after conditioning on the rest of the available information?

If before, there's gotta be statistics out there. What fraction of people charged plead guilty? What fraction that plead not guilty are convicted?

What fraction of convicts are eventually proven innocent?

Comment author: Morendil 10 December 2009 03:27:25PM *  1 point [-]

The first site below suggests US wrongful conviction rates range from .5 percent to 10 percent. It cites for the lower rate a source who I think is the author of the next URL:

http://www.caught.net/innoc.htm

http://www.abanet.org/crimjust/spring2003/conviction.html

I would be very surprised if Italy's legal system turned out to have a significantly worse rate.

"Convicts eventually proven innocent" is, sadly, bound to be a lower fraction than wrongful conviction rate - i.e. you get wrongful conviction rates by extrapolating one way or another from attested cases.

Comment author: jimmy 10 December 2009 07:35:08PM 0 points [-]

Thanks for the link. I get that "Convicts eventually proven innocent" is most likely a lower bound (probably not too many guilty ones later exonerated?), but I figured I'd have to work from there to get a crude guess.

On one hand, even 10% isn't all that bad in an absolute sense- most of the deterrent is being had with not too much additional waste. On the other, that means that our trial and jury system is probably worse than I thought, if it's true that "most" people charged with a crime plead guilty.

I'll look up the statistics and report back in a couple days.

Comment author: ciphergoth 10 December 2009 08:36:15AM 0 points [-]

I'm inclined to believe that in general it's very strong - that if all you know about X is that they were convicted of rape and murder, then the likelihood that they raped and murdered someone is vastly greater.

In this particular case, adding it to the other things I've skimmed about it, I'm coming to something like a .20/.20/.70 estimate, but that's after reading the comments here.

Comment author: Douglas_Knight 10 December 2009 03:43:38PM 2 points [-]

I'm inclined to believe that in general it's very strong - that if all you know about X is that they were convicted of rape and murder, then the likelihood that they raped and murdered someone is vastly greater.

Yes...but that's never all you know, unless you visit a prison. Otherwise, something has drawn your attention to the particular person, which is a lot of information. In particular, my prior for the innocence of people whose conviction is a cause celebre is 75%.

Comment author: jimmy 10 December 2009 12:50:22AM *  1 point [-]

The fact that my first two probabilites were as high as they were has more to do with the minimal time spent and tired mental state I was in (eg I had trouble even keeping the relevant evidence in my short term memory) and fully expected later estimates based on further processing the same information to be much more extreme.

I did significantly revise my probability due to low priors on that sort of 3 person crime once I decided Guede was guilty, but I didn't trust myself enough at the time to put a prior on it that was that low nor really keep track of evidence.

Still though, I probably could have guessed which side the answer would fall on and should have put something somewhat lower.

Comment author: mattnewport 10 December 2009 01:01:24AM *  4 points [-]

I had a quick look for some statistics to verify my priors that both female on female murder and multiple offender murder are unusual. These data seem relevant: gender; multiple offenders. These appear to back up my intuition that finding a very likely male suspect (Guede) should have greatly reduced the prosecution's odds for the guilt of a female suspect (Knox) in a multiple offender attack. A plausible case for a male offender committing the crime alone should greatly lower the probability of guilt of a female suspect acting either alone or as an accomplice.

Comment author: jimmy 10 December 2009 01:42:12AM 3 points [-]

Agreed. The only reason that this might not drive down the probability of Knoxs guilt is that there's some chance that the system is behaving somewhat rationally, and the fact that they were convicted is evidence that there's information that you don't have.

Of course, once you hear all the prosecutors arguments, that goes away.

That brings up an interesting question though. If the base rate is low enough and base rate neglect is common enough, maybe you really can confidently claim that Knox is innocent even though she was convicted given only the fact that Guede is guilty and plausibly could have done it himself.

Comment author: gwern 10 December 2009 10:56:43PM 0 points [-]

If the base rate is low enough and base rate neglect is common enough, maybe you really can confidently claim that Knox is innocent even though she was convicted given only the fact that Guede is guilty and plausibly could have done it himself.

I'd love to see an article doing the research to make this claim. At the very least, I'd be entertained.

Comment author: lordweiner27 10 December 2009 02:08:17AM *  1 point [-]

Sure this type of murder is rare, otherwise it wouldn't have made the news. That's not evidence the other two aren't guilty. Not when we have her hand on the knife and his foot in her blood.

Comment author: lordweiner27 10 December 2009 02:10:51AM 0 points [-]

The wikipedia article states that Guede was known to the couple and to the others in their house.

Comment author: mattnewport 10 December 2009 02:33:53AM 0 points [-]

The Wikipedia page seems to be changing quite a lot at the moment. The impression I got from the various sources was that Guede was acquainted with the people who lived on the 1st floor of the building (not house mates but neighbours of Knox and the victim) and Knox said she recognized him but that Sollecito claimed never to have met him. I haven't seen any claims that they were friends but there was an eye witness who claimed to have seen them together. There seems to be some dispute over whether they had ever previously met or talked with each other but no claim from the prosecution that there was any kind of longer term association between them prior to the murder.

Comment author: nerzhin 09 December 2009 05:12:58PM 1 point [-]

I'm putting myself in the "low familiarity" category.

  1. estimate Amanda Knox is guilty: 40%
  2. estimate Raffaele Sollecito is guilty: 40%
  3. estimate Rudy Guede is guilty: 90%
  4. not confident at all that my estimates correspond to komponisto's

I got most of my information from the "defendants are innocent" link and the Wikipedia article - I found the "defendants guilty" link hard to read or assess. I did not spend much time forming my opinion, just a quick browse.

Comment author: bentarm 09 December 2009 11:12:42AM 1 point [-]
  1. 5%
  2. 5%
  3. 95%
  4. probably generally the same - you might be more or less extreme.
  5. The sources are the two sites you linked to, plus the wikipedia article plus my impression that 1 man killing a girl in a sexual assault is a priori much more likely than three relatively recent acquaintances doing same.

NB - 5% and 95% are basically just proxies for 'pretty sure it's not true' and 'pretty sure it's true'. I wouldn't claim that they're anything like well-calibrated. I don't think I form opinions on stories like this often enough to be well-calibrated.

Oh, and I second the opinion that this is exactly the sort of thing that LW needs more of - people actually attempting to see how good they are at being right about the world (although maybe issues in which it's easier to be sure of the "right answer" would be better tests).

Comment author: AngryParsley 09 December 2009 07:59:01AM *  1 point [-]

I had heard a little about this case before you brought it up, but I didn't want to read about it since I figured I'd get angry about either: 1. Yet another travesty of justice. or: 2. Yet another obviously guilty person being cast in a good light. It was the former. Unrecorded interrogations without a lawyer. No forensic evidence putting Knox in the room. No motive, no sequestered jury, tons of disputes about forensics. What a mess.

Your probability estimate that Amanda Knox is guilty.

0.2

Your probability estimate that Raffaele Sollecito is guilty.

0.25

Your probability estimate that Rudy Guede is guilty.

0.9

How much you think your opinion will turn out to coincide with mine.

I think we'll be rather close. Basically, low probabilities for Knox and Sollecito, and a very high probability for Guede.

Comment author: mattnewport 09 December 2009 07:32:16AM *  1 point [-]

I'm moderately familiar with the case (have read a few media articles on the case over the last few months).

  1. 10% (weak evidence, lack of motive, low prior probability of female on female sexually motivated violence)
  2. 30% (evidence not much better, higher prior probability of male on female sexually motivated violence)
  3. 50% (seems to fit profile of this type of offence, evidence of association with victim and opportunity and circumstantial evidence)
  4. I expect your relative rankings to be the same, less confidence in absolute probabilities.
  5. Fairly mainstream media sources, probably linked from blogs I read which will likely supply a selection bias, don't remember exactly what the sources were.
Comment author: mattnewport 09 December 2009 08:16:38AM 1 point [-]

After reading a bit more I'd revise my probabilities to:

  1. 5%
  2. 10%
  3. 90%

The evidence against Knox and Sollecito is very weak and there doesn't seem to be clear motive. The evidence against Guede is strong and it seems clear that had he been identified initially as the primary suspect there would have been no reason for the police to suspect anyone else was involved in the attack.

I think there's a very high probability Guede is the only guilty party. There is a small probability that all 3 conspired in some way and an even smaller probability that Knox and Sollecito conspired together.

Comment author: michaelsullivan 11 December 2009 09:17:38PM 1 point [-]

The spread between the base prior for male on female sexual violence vs. female on female sexual violence is nowhere near enough to separate the percentages for Knox and Sollecito this widely, let alone as widely as in your first cut.

The general prior may be 2-3 times as likely, but that spread should not hold up after a lot of additional evidence to consider where they are essentially equal. Every piece of evidence that counts for or against them roughly equally should shrink that spread in ratio terms. And it should not expand it in absolute terms at all either. Given that these priors are extremely low (or should be), well under 1% for male or female, there shouldn't be more than a 1% spread in those simply from that prior. Only evidence which would amplify the male v. female disparity in prior, or evidence that specifically argues in favor of S's but not K's guilt, should get you to a spread of more than 1% between them.

Comment author: mattnewport 11 December 2009 10:11:42PM *  1 point [-]

According to this page, only 6.4% of offenders in sex related homicides are female (lower than the 11.2% of all homicide offenders who are female). Of all homicides only 2.4% are female on female. I can't see a simple way to derive the percentage of female offenders in sex related homicides with a female victim but it seems likely based on the other numbers to be lower than p(Female Offender|Female Victim) which I make to be 9.6%: p(FO|FV) = p(FV|FO)*p(FO)/p(FV) = 2.4 / (2.4 + 22.7) = 0.096.

So given no other information, if you know you have a female victim in a sex related homicide it would be reasonable to assume that it is at least 10 times more likely that the murderer is male. About 91% of female murder victims are killed by someone known to the victim so it is reasonable for the police to start with her close associates. Given no particular reason to favour Knox or Sollecito as the murderer you would put much higher odds on it being Sollecito purely based on his gender.

That was roughly the reasoning I used with my initial estimates. I hadn't looked up any statistics at that point, I just knew that a female murder victim was significantly more likely to have been killed by a male than by a female, especially if there appeared to be a sexual motive to the murder. In light of the statistics I think if anything I should have put a wider gap on the estimates in the absence of other evidence implicating one over the other.

Comment author: DanArmak 11 December 2009 10:24:32PM *  1 point [-]

About 91% of female murder victims are killed by someone known to the victim so it is reasonable for the police to start with her close associates.

I don't know anything about this specific case, but in general - we need to adjust this kind of statement for selection bias, and I would like to know how this is done.

When killers aren't known to the victims, the police are less likely to find them both because they don't look for them (as you said) and because there are too many people the victim didn't know for the police to examine more than a small fraction.

Therefore I expect the just conviction rate in these crimes to be lower, and the false conviction rate to be higher (the police are always likely to accuse and help convict someone the victim knew, but in these cases we know such an accused is innocent).

However, your statistic (many murder victims knew their attacker) probably actually counts convictions. How should we revise this due to A) false convictions and B) a different-than-general rate of crimes solved (where conviction was achieved, or the primary suspect died or fled)? If the statistic already takes such considerations into account, how it this done?

Comment author: badger 09 December 2009 06:31:39AM *  1 point [-]

I have never heard of this case before this post. After approximately 30 minutes of reading the two sites you linked to as well as the Wikipedia article, my current estimates are:

  • Knox guilty: 0.35
  • Sollecito guilty: 0.35
  • Guede guilty: 0.80

I think your opinion will roughly coincide with mine about Guede, but could differ dramatically about the other two.

Comment author: badger 09 December 2009 10:17:14PM 1 point [-]

Update: After reading the other comments here, I'm revising to

  • Knox guilty: 0.20
  • Sollecito guilty: 0.20
  • Guede guilty: 0.70
  • None of the three: 0.20
Comment author: TraderJoe 09 October 2012 07:02:07AM *  0 points [-]

[comment deleted] 4. How much you think your opinion will turn out to coincide with mine - hard to define. If your respective answers are 10, 40, 90, how much did we agree? I'll guess that the sum of the three differences between my answers and yours is around sixty percentage points [out of 300 possible].

Comment author: vancouvermom 31 December 2010 01:41:35AM 0 points [-]

How does one get to vote? I say, not guilty except Guede. What an embarrassment and nobody wants to admit their crooked government employees are nuts and criminals. Someone needs to look closely at Mignini and his motives, He sounds like a religious nut whose small mind saw one thing and then spoon fed the tabloids. And found guilty of "crimes in regard to evidence". This is a complex case. These two do not deserve to be in jail. Guede does and then the Perugian Magistrate, prosecutor and the tabloids should be held accountable for the crimes against these two. The Anti-american bias and bigotry, the ridiculous deal made with Guede, the ridiculous "slander" suits, Amanda should bring her own, if this doesn't scream slander........hope the people see the truth, even if an attorney who really has nothing but money to gain, he represents most of the "slander" suit plaintiffs and will then be awarded money against those monetary awards. Does he have a "Knox" motive? You know, the motive where you are judged, tried in the papers then smacked around, sleep deprived, food deprived, ATTORNEY deprived.....you can't tell them any other way, become the easiest target by finding a problem, calling the police. A truer criminal you will never find? She didn't exactly fight against the review of the forensics and DNA, a guilty person would probably be pretty upset. Just a little DNA in the wrong place...Oh, Rudy Guede and his huge amount of DNA that was found including feet and handprints, then their is that hair and sexual stuff...... This case is the one in a million where jurors were probably threatened to vote guilty, See how that baseless rumor starts.........Hmmmm I do wonder just what is true, with the now tainted background of the prosecutor and his lady friend. Just a thought

Comment author: michellesings 26 April 2010 07:05:40AM 0 points [-]

I find it a very simple case with tons of evidence and tons of lack of evidence that point to freedom. And to something SERIOUSLY wrong somewhere. I love America, I love Italy, I love truth and hate injustice. Fact over opinion. Show many facts...

Comment author: erica 18 December 2009 11:18:26AM 0 points [-]

I'd love to know what Amanda and Raffaelle got up to that night but the lack of DNA in the room and on the body suggests that whatever they did, they weren't in the room or directly responsible for the death, and nor did they go back in the room to move the body around - that would require head to toe covering. But...

Did Amanda and Raffaelle sit in the flat egging Guede on, not realising the screams were real? Or, worse, did they laugh knowlingly when they heard screams?

What would they be guilty of? Would either scenario count as murder?

Did they feel so sure that they would be acquitted that they didn't own up to being in the flat?

If they owned up now, could the courts increase the sentence to 30 years for having perjured themselves, even if it wasn't classed as murder?

Or, are they just two idiotic and/or idealistic students who don't make sense, can't make sense?

Comment author: wnoise 13 December 2009 05:40:32PM 0 points [-]

Not very familiar -- had heard about it, but no real details.

I'll echo all those that have raised concerns about prosecutorial and police misconduct, releasing details that later turned out not to be true, or were entirely irrelevant. The group sex games focus also reminds me strongly of many other moral panic cases where people flip out for no good reason.

I don't find the "cleaning" hypothesis very well supported -- it's hard to selectively clean, which would be necessary to eliminate all of their own evidence, but still leave so much Guede evidence.

overall: P(Knox) ~ 0.02 P(Sollecito) ~ 0.02 P(Guede) ~ 0.98

Comment author: ChrisHibbert 12 December 2009 06:35:54PM 0 points [-]

I was aware of the case before, but hadn't looked into it in any detail. My reaction to the sites is that the site arguing innocence seems to be presenting facts and showing contradictions in the other side's arguments. I couldn't find any consistent argument on the other side. There were many scenarios, with inconsistent adherence to the facts, lots of innuendo and plausibility arguments for particular claims, but no coherent story.

  1. Your probability estimate that Amanda Knox is guilty. less than 30%
  2. Your probability estimate that Raffaele Sollecito is guilty. less than 30%
  3. Your probability estimate that Rudy Guede is guilty. more than 40%
  4. How much you think your opinion will turn out to coincide with mine. It seems likely. more than 75% overlap, if that means anything.
Comment author: brazil84 12 December 2009 02:08:57PM *  0 points [-]

I basically agree with Lordweiner. 90/90/99.

It seems pretty clear that AK and RS were and are hiding something damaging to them. Their stories are just too changing and contradictory.

That damaging fact is almost certainly that they were involved in the murder. Because if it were something else, they would have to be insane not to come clean about it.

ETA: I came up with my estimate before reading anyone's posts.

Comment author: Sebastian_Hagen 11 December 2009 10:11:32PM *  0 points [-]

I don't remember hearing about this case before reading this post. This is not strong evidence that I hadn't; it's the kind of news item I'd be likely to classify as "contains no valuable or interesting information" (no disrespect to the victim, her friends or her relatives is intended; but the global death rate is such that you just can't keep up with all the individual instances, and therefore you necessarily have to be extremely selective about which individual deaths receive any specific attention from you) and discard immediately from memory. In any case I don't have any significant prior case-specific knowledge.

I've consulted the Wikipedia article, one of the news articles used as a primary source by said article, read most of entries from the TJ Prosecution's Case category, as well as the FOA pages. Altogether I spent a few hours on this research.

I accidentally looked at one response (IIRC it was this one) before I read the post itself, and learned that that had been a bad move. I'll do my best to filter that knowledge out of my answer. Since there's accusations of Anti-US bias flying around, I should probably also mention that I'm a citizen of (and live in) Germany. I don't think I'm biased against US citizens, but such self-assessment is always tricky.

Given all of that, here's my answers:

  1. 0.8
  2. 0.8
  3. 0.9
  4. It's hard to quantify this precisely. I expect about a 80% chance of you agreeing that the probability for 3 is >= 0.75, and around a 60% chance of you assigning probabilities of >= 0.6 to both of 1 and 2.

Reasoning:

  • 1 and 2: Suspects' behavior as documented by their phone and computer use doesn't match their preferred stories. AK correctly mentioning MK screaming is some evidence that she was at the scene of the crime. FOA attacks the DNA test performed on the knife, but the experts responsible appear to think that this kind of testing is reliable under the circumstances, and they should be in a good position to judge. The jury in the case had better access to the evidence available (apparently presenting all of it took on the order of 200 hours; this suggests there's quite a lot of the stuff), and much more cputime to process it than I do; in absence of strong evidence that their reasoning was fundamentally flawed, their judgement is strong empirical evidence for the guilt of the defendants.

  • 3: Pretty good evidence there; lots of DNA material, and RG's story sounds rather unlikely. And again, there's an existing judgement by someone who had better access to information and more time to think about the issue.

General comments:

This is quite a mess. Both of the advocacy sites are contaminated with lots of data that's so weakly relevant as to be basically a distraction. So are the newspaper articles. Why exactly do we need photos of the people involved? Even hypothetically, what does this kind of information add to the discussion? The character testimonies are only marginally better; theoretically that kind of thing is evidence, in practice it's so weak as to be likely to do more harm than good. This whole case is an affect minefield. I guess this does make this a great real-life rationality stress test, but somehow I doubt that that was what the people who put those documents together had in mind.

Comment author: Sebastian_Hagen 11 December 2009 11:25:26PM *  2 points [-]

It turns out most commentors are of a rather different opinion on 1. and 2., so ... update time!

New evidence includes reports that use of the involved drugs does significantly impair memory, a reminder that absence of evidence is evidence of absence, and fairly damning judgements about the Italien legal system. I also realized that my priors for P(group rape | rape) and P(group murder | murder) were insufficiently extreme (i.e. too high).

All of this is fairly general evidence about such cases, so the jury could well have had access to it, as well. They're still in a position of having much better access to evidence, and the real question becomes how rational they are in evaluating it.

Updated probabilities are:

  1. 0.35
  2. 0.35
  3. 0.9
Comment author: JamesAndrix 10 December 2009 10:36:59PM *  0 points [-]

1:25% 2:25% 3:50% 4:60% on 1&2

I knew virtually nothing about this an hour ago.

Comment author: imaxwell 10 December 2009 05:55:08PM *  0 points [-]

I didn't know anything about this case until I read this post.

My first impression: Wow, there sure is a lot of information on what a nice person Meredith Kercher was on that one site, and what a nice person Amanda Knox is on that other site. (The latter is at least potentially relevant, if you think a nasty person is more likely to kill someone.)

Anyway: Knox : ~35%; Sollecito : ~35%; Guede : ~95%. And I'd say it's about 60% that all of these probabilities are on the same side of 50% as yours.

(I had a bunch of information here on how I came to my opinion, but I don't think it's really important. Suffice it to say that the evidence I've seen against Ms. Knox and Mr. Sollecito is pretty terrible, but the evidence I haven't seen may be much better.)

Anyway, if those are the best, clearest sources available to me then I am pretty doubtful of my ability to form a useful opinion on this case at all.

Comment author: Miedvied 10 December 2009 03:42:57PM 0 points [-]

Both sites are sources of information presented by people with extremely strong emotional investments in the case. The Guilty site seems to be populated by nothing but emotional arguments (even looking through the Micheli Report link only produced second-hand commentary couched in strong emotional terms, i.e., "our translators cried..."). The innocent site is less emotional. Neither provide objective third-party sources of information, so taking either side's arguments as "facts" seems to be undertaking a bias to begin with.

Even after killing an hour going through the sites, I'd have to abstain.

Comment author: Nanani 10 December 2009 05:10:47AM 0 points [-]

I attempted the test with zero familiarity with the case at hand. I also have very little knowledge of the Italian justice system.

One major problem in presenting a probability assessement is that the links presented in the post offer pratically no facts about the case. They are about a Washington Senator's reaction, instead. It would be ludicrous to answer the questions asked given only this information.

So, I went googling around for more information. I promptly hit a snag in that I do not what a fast-track trial is in the context of Italy, and searching for information on that is made very difficult since the search returns articles on the Kercher case.

Attempting to filter out all the extra fluff about the characters involved, the facts of the case, most especially the DNA, seems to point to Guede. There is no hard evidence supporting Knox's guilt, and Sollecito's DNA on the victim's bra is not suprising given their relationship.

Unless the links I read (mostly obtained via Wikipedia) managed to omit something important, I'd say the following:

Knox guilty: less than 0.1 Sollecito: 0.1 to 0.15 Guede: 0.9

Comment author: komponisto 10 December 2009 06:12:57AM *  1 point [-]

One major problem in presenting a probability assessement is that the links presented in the post offer pratically no facts about the case. They are about a Washington Senator's reaction, instead. It would be ludicrous to answer the questions asked given only this information.

You must have only looked at the front pages of the two sites. You have to browse around somewhat to find the information.

I suggest starting here on Friends of Amanda, and here on True Justice.

Comment author: Eliezer_Yudkowsky 10 December 2009 09:04:08AM 11 points [-]

You should have sent the readers directly to that information, then. LW has thousands of readers, so putting in 10X work yourself to save thousands of readers X time is generally a good idea.

Comment author: komponisto 11 December 2009 06:49:16AM 1 point [-]

Well, as I said, the information is not all in one place (particularly on TJ; FoA is better organized), and I was worried about biasing readers via my selection of the first page to read. (In fact, as I indicated in the post, I was even somewhat worried about biasing readers via my selection of the sites themselves.)

Most of the commenters seem not to have had problems. For the few that did, I don't mind giving a little more direction to them individually.

Comment author: gwern 10 December 2009 10:33:42PM *  0 points [-]

What makes you think that Sollecito is more likely to be guilty than Knox, and possibly more than 15x likely? (Which is quite the difference.)

What likely scenarios are you envisioning that have Guede and Sollecito murdering her without Knox being involved? It seems to me that all the plausible or presented scenarios have Sollecito & Knox acting in concert or in some way covering up for the other, and so their guilts would be closely linked.

Comment author: Nanani 11 December 2009 01:26:13AM *  0 points [-]

What makes you think that Sollecito is more likely to be guilty than Knox

Simple. Sollecito's DNA was found there, but not Knox's. I think it highly unlikely that the DNA has any link to the actual murder, but its presence justifies an allowance of probability mass.

Less than 0.1 and 0.15 are both very low probabilities.

Comment author: kodos96 10 December 2009 11:47:37PM 0 points [-]

Ahhhh... 0.15 isn't 15x 0.1

It's probably justified simply by priors re male/female committing rape/murder

Comment author: gwern 10 December 2009 11:55:56PM 0 points [-]

<0.1 includes values like 0.00000001, y'know. So technically I'm not wrong... But you're right, I saw .1 and .15 and forgot that that was 1.5x, not 15x. (That would require .01)

Comment author: wedrifid 10 December 2009 04:10:19AM 0 points [-]
  1. Your probability estimate that Amanda Knox is guilty.

0.05

  1. Your probability estimate that Raffaele Sollecito is guilty.

0.05

  1. Your probability estimate that Rudy Guede is guilty.

0.9

  1. How much you think your opinion will turn out to coincide with mine.

p(same direction) = 0.6

p(someone in the prosecution is guilty of actions I would give live imprisonment for) = 0.99.

Comment author: zero_call 10 December 2009 01:26:32AM 0 points [-]

It's good that you gave two separate links to look at both sides of the case. However, I really disagree with you suggesting people to look at wikipedia. Wikipedia is known to be horrifically unreliable when it comes to controversial topics. This much can easily be seen just by scrolling through the article's "discussion" subpage, which contains a lot of ouright allegations of impartiality from various wikipedia editors. I've seen a few people posting their assessments based on their reading of wikipedia, and this is a big problem.

For further illustration of the impartiality of wikipedia in controversial topics, perhaps the best example I have seen is the article for second hand smoking, which they label as "passive smoking" (http://en.wikipedia.org/wiki/Passive_smoking). See pertinent criticism at (http://tech.slashdot.org/comments.pl?sid=1346195&cid=29182695). If you read the article (and the commentary subpage), it is pretty outlandish how one-sided it is.

You need to actively discourage people from looking at wikipedia for this sort of thing...