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The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom

42 Post author: komponisto 13 December 2009 04:16AM

Note: The quantitative elements of this post have now been revised significantly.

Followup to: You Be the Jury: Survey on a Current Event

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 [other commenters] certain they're wrong seems laughable

- lordweiner27, commenting on my previous post

The short answer: it's very much like how a few minutes of philosophical reflection trump a few millennia of human cultural tradition.

Wielding the Sword of Bayes -- or for that matter the Razor of Occam -- requires courage and a certain kind of ruthlessness. You have to be willing to cut your way through vast quantities of noise and focus in like a laser on the signal.

But the tools of rationality are extremely powerful if you know how to use them.

Rationality is not easy for humans. Our brains were optimized to arrive at correct conclusions about the world only insofar as that was a necessary byproduct of being optimized to pass the genetic material that made them on to the next generation. If you've been reading Less Wrong for any significant length of time, you probably know this by now. In fact, around here this is almost a banality -- a cached thought. "We get it," you may be tempted to say. "So stop signaling your tribal allegiance to this website and move on to some new, nontrivial meta-insight."

But this is one of those things that truly do bear repeating, over and over again, almost at every opportunity. You really can't hear it enough. It has consequences, you see. The most important of which is: if you only do what feels epistemically "natural" all the time, you're going to be, well, wrong. And probably not just "sooner or later", either. Chances are, you're going to be wrong quite a lot.

To borrow a Yudkowskian turn of phrase: if you don't ever -- or indeed often -- find yourself needing to zig when, not only other people, but all kinds of internal "voices" in your mind are loudly shouting for you to zag, then you're either a native rationalist -- a born Bayesian, who should perhaps be deducing general relativity from the fall of an apple any minute now -- or else you're simply not trying hard enough.    

Oh, and another one of those consequences of humans' not being instinctively rational?

Two intelligent young people with previously bright futures, named Amanda and Raffaele, are now seven days into spending the next quarter-century of their lives behind bars for a crime they almost certainly did not commit.

"Almost certainly" really doesn't quite capture it. In my previous post I asked readers to assign probabilities to the following propositions:

1. Amanda Knox is guilty (of killing Meredith Kercher)
2. Raffaele Sollecito is guilty (of killing Meredith Kercher)
3. Rudy Guédé is guilty (of killing Meredith Kercher)

I also asked them to guess at how closely they thought their estimates would match mine.

Well, for comparison, here are mine (revised):

1. Negligible. Small. Hardly different from the prior, which is dominated by the probability that someone in whatever reference class you would have put Amanda into on January 1, 2007 would commit murder within twelve months. Something on the order of 0.001 0.01 or 0.1 at most.  
2. Ditto.
3. About as high as the other two numbers are low. 0.999 0.99 as a (probably weak) lower bound.

Yes, you read that correctly. In my opinion, there is for all intents and purposes zero Bayesian evidence that Amanda and Raffaele are guilty. Needless to say, this differs markedly from the consensus of the jury in Perugia, Italy. 

How could this be?

Am I really suggesting that the estimates of eight jurors -- among whom two professional judges -- who heard the case for a year, along with something like 60% of the Italian public and probably half the Internet (and a significantly larger fraction of the non-American Internet), could be off by a minimum of three orders of magnitude (probably significantly more) such a large amount? That most other people (including most commenters on my last post) are off by no fewer than two?

Well, dear reader, before getting too incredulous, consider this. How about averaging the probabilities all those folks would assign to the proposition that Jesus of Nazareth rose from the dead, and calling that number x. Meanwhile, let y be the correct rational probability that Jesus rose from the dead, given the information available to us.

How big do you suppose the ratio x/y is?

Anyone want to take a stab at guessing the logarithm of that number?

Compared to the probability that Jesus rose from the dead, my estimate of Amanda Knox's culpability makes it look like I think she's as guilty as sin itself.

And that, of course, is just the central one of many sub-claims of the hugely complex yet widely believed proposition that Christianity is true. There are any number of other equally unlikely assertions that Amanda would have heard at mass on the day after being found guilty of killing her new friend Meredith (source in Italian) -- assertions that are assigned non-negligible probability by no fewer than a couple billion of the Earth's human inhabitants.

I say this by way of preamble: be very wary of trusting in the rationality of your fellow humans, when you have serious reasons to doubt their conclusions.

The Lawfulness of Murder: Inference Proceeds Backward, from Crime to Suspect

We live in a lawful universe. Every event that happens in this world -- including human actions and thoughts -- is ultimately governed by the laws of physics, which are exceptionless. 

Murder may be highly illegal, but from the standpoint of physics, it's as lawful as everything else. Every physical interaction, including a homicide, leaves traces -- changes in the environment that constitute information about what took place.

Such information, however, is -- crucially -- local. The further away in space and time you move from the event, the less entanglement there is between your environment and that of the event, and thus the more difficult it is to make legitimate inferences about the event. The signal-to-noise ratio decreases dramatically as you move away in causal distance from the event. After all, the hypothesis space of possible causal chains of length n leading to the event increases exponentially in n.

By far the most important evidence in a murder investigation will therefore be the evidence that is the closest to the crime itself -- evidence on and around the victim, as well as details stored in the brains of people who were present during the act. Less important will be evidence obtained from persons and objects a short distance away from the crime scene; and the importance decays rapidly from there as you move further out.

It follows that you cannot possibly expect to reliably arrive at the correct answer by starting a few steps removed in the causal chain, say with a person you find "suspicious" for some reason, and working forward to come up with a plausible scenario for how the crime was committed. That would be privileging the hypothesis. Instead, you have to start from the actual crime scene, or as close to it as you can get, and work backward, letting yourself be blown by the winds of evidence toward one or more possible suspects.

In the Meredith Kercher case, the winds of evidence blow with something like hurricane force in the direction of Rudy Guédé. After the murder, Kercher's bedroom was filled with evidence of Guédé's presence; his DNA was found not only on top of but actually inside her body. That's about as close to the crime as it gets. At the same time, no remotely similarly incriminating genetic material was found from anyone else -- in particular, there were no traces of the presence of either Amanda Knox or Raffaele Sollecito in the room (and no, the supposed Sollecito DNA on Meredith's bra clasp just plain does not count -- nor, while we're at it, do the 100 picograms [about one human cell's worth] of DNA from Meredith allegedly on the tip of a knife handled by Knox, found at Sollecito's apartment after the two were already suspects; these two things constituting pretty much the entirety of the physical "evidence" against the couple).

If, up to this point, the police had reasons to be suspicious of Knox, Sollecito, and Guédé, they should have cleared Knox and Sollecito at once upon the discovery that Guédé -- who, by the way, was the only one to have fled the country after the crime -- was the one whom the DNA matched. Unless, that is, Knox and Sollecito were specifically implicated by Guédé; after all, maybe Knox and Sollecito didn't actually kill the victim, but instead maybe they paid Guédé to do so, or were otherwise involved in a conspiracy with him. But the prior probabilities of such scenarios are low, even in general -- to say nothing of the case of Knox and Sollecito specifically, who, tabloid press to the contrary, are known to have had utterly benign dispositions prior to these events, and no reason to want Meredith Kercher dead.

If Amanda Knox and Raffaele Sollecito were to be in investigators' thoughts at all, they had to get there via Guédé -- because otherwise the hypothesis (a priori unlikely) of their having had homicidal intent toward Kercher would be entirely superfluous in explaining the chain of events that led to her death.  The trail of evidence had led to Guédé, and therefore necessarily had to proceed from him; to follow any other path would be to fatally sidetrack the investigation, and virtually to guarantee serious -- very serious -- error. Which is exactly what happened.

There was in fact no inferential path from Guédé to Knox or Sollecito. He never implicated either of the two until long after the event; around the time of his apprehension, he specifically denied that Knox had been in the room. Meanwhile, it remains entirely unclear that he and Sollecito had ever even met.

The hypotheses of Knox's and Sollecito's guilt are thus seen to be completely unnecessary, doing no explanatory work with respect to Kercher's death. They are nothing but extremely burdensome details.  

Epistemic Ruthlessness: Following the Strong Signal

All of the "evidence" you've heard against Knox and Sollecito -- the changing stories, suspicious behavior, short phone calls, washing machine rumors, etc. -- is, quite literally, just noise.

But it sounds so suspicious, you say. Who places a three-second phone call? 

As humans, we are programmed to think that the most important kinds of facts about the world are mental and social -- facts about what humans are thinking and planning, particularly as regards to other humans. This explains why some people are capable of wondering whether the presence of (only) Rudy Guédé's DNA in and on Meredith's body should be balanced against the possibility that Meredith may have been annoyed at Amanda for bringing home boyfriends and being insufficiently tidy  -- that might have led to resentment on Amanda's part, you see.

That's an extreme example, of course -- certainly no one here fell into that kind of trap. But at least one of the most thoughtful commenters was severely bothered by the length of Amanda's phone calls to Meredith. As -- I'll confess -- was I, for a minute or two.

I don't know why Amanda wouldn't have waited longer for Meredith to pick up. (For what it's worth, I myself have sometimes, in a state of nervousness, dialed someone's number, quickly changed my mind, then dialed again a short time later.) But -- as counterintuitive as it may seem -- it doesn't matter. The error here is even asking a question about Amanda's motivations when you haven't established an evidentiary (and that means physical) trail leading from Meredith's body to Amanda's brain. (Or even more to the point, when you have established a trail that led decisively elsewhere.)

Maybe it's "unlikely" that Amanda would have behaved this way if she were innocent. But is the degree of improbability here anything like the improbability of her having participated in a sex-orgy-killing without leaving a single piece of physical evidence behind? While someone else left all kinds of traces? When you had no reason to suspect her at all without looking a good distance outside Meredith's room, far away from the important evidence?

It's not even remotely comparable. 

Think about what you're doing here: you are invoking the hypothesis that Amanda Knox is guilty of murder in order to explain the fact that she hung up the phone after three seconds. (Remember, the evidence against Guédé is such that the hypothesis of her guilt is superfluous -- not needed -- in explaining the death of Meredith Kercher!)

Maybe that's not quite as bad as invoking a superintelligent deity in order to explain life on Earth; but it's the same kind of mistake: explaining a strange thing by postulating a far, far stranger thing.

"But come on," says a voice in your head. "Does this really sound like the behavior of an innocent person?"

You have to shut that voice out. Ruthlessly. Because it has no way of knowing. That voice is designed to assess the motivations of members of an ancestral hunter-gather band. At best, it may have the ability to distinguish the correct murderer from between 2 and 100 possibilities -- 6 or 7 bits of inferential power on the absolute best of days. That may have worked in hunter-gatherer times, before more-closely-causally-linked physical evidence could hope to be evaluated. (Or maybe not -- but at least it got the genes passed on.)

DNA analysis, in contrast, has in principle the ability to uniquely identify a single individual from among the entire human species (depending on how much of the genome is looked at; also ignoring identical twins, etc.) -- that's more like 30-odd bits of inferential power. In terms of epistemic technology, we're talking about something like the difference in locomotive efficacy between a horsedrawn carriage and the Starship Enterprise. Our ancestral environment just plain did not equip our knowledge-gathering intuitions with the ability to handle weapons this powerful.

We're talking about the kind of power that allows us to reduce what was formerly a question of human social psychology -- who made the decision to kill Meredith? -- to one of physics. (Or chemistry, at any rate.)

But our minds don't naturally think in terms of physics and chemistry. From an intuitive point of view, the equations of those subjects are foreign; whereas "X did Y because he/she wanted Z" is familiar. This is why it's so difficult for people to intuitively appreciate that all of the chatter about Amanda's "suspicious behavior" with various convincing-sounding narratives put forth by the prosecution is totally and utterly drowned out to oblivion by the sheer strength of the DNA signal pointing to Guédé alone.

This rationalist skill of following the strong signal -- mercilessly blocking out noise -- might be considered an epistemic analog of the instrumental "shut up and multiply": when much is at stake, you have to be willing to jettison your intuitive feelings in favor of cold, hard, abstract calculation.

In this case, that means, among other things, thinking in terms of how much explanatory work is done by the various hypotheses, rather than how suspicious Amanda and Raffaele seem

Conclusion: The Amanda Knox Test

I chose the title of this post because the parallel structure made it sound nice. But actually, I think an hour is a pretty weak upper bound on the amount of time a skilled rationalist should need to arrive at the correct judgment in this case.

The fact is that what this comes down to is an utterly straightforward application of Occam's Razor. The complexity penalty on the prosecution's theory of the crime is enormous; the evidence in its favor had better be overwhelming. But instead, what we find is that the evidence from the scene -- the most important sort of evidence by a huge margin -- points with literally superhuman strength toward a mundane, even typical, homicide scenario. To even consider theories not directly suggested by this evidence is to engage in hypothesis privileging to the extreme.

So let me say it now, in case there was any doubt: the prosecution of Amanda Knox and Raffaele Sollecito, culminating in last week's jury verdict -- which apparently was unanimous, though it didn't need to be under Italian rules -- represents nothing but one more gigantic, disastrous rationality failure on the part of our species.

How did Less Wrong do by comparison? The average estimated probability of Amanda Knox's guilt was 0.35 (thanks to Yvain for doing the calculation). It's pretty reasonable to assume the figure for Raffaele Sollecito would be similar. While not particularly flattering to the defendants (how would you like to be told that there's a 35% chance you're a murderer?), that number makes it obvious we would have voted to acquit. (If a 65% chance that they didn't do it doesn't constitute  "reasonable doubt" that they did...)

The commenters whose estimates were closest to mine -- and, therefore, to the correct answer, in my view -- were Daniel Burfoot and jenmarie. Congratulations to them. (But even they were off by a factor of at least ten!)

In general, most folks went in the right direction, but, as Eliezer noted, were far too underconfident -- evidently the result of an exorbitant level of trust in juries, at least in part. But people here were also widely making the same object-level mistake as (presumably) the jury: vastly overestimating the importance of "psychological" evidence, such as Knox's inconsistencies at the police station, as compared to "physical" evidence (only Guédé's DNA in the room).

One thing that was interesting and rather encouraging, however, is the amount of updating people did after reading others' comments -- most of it in the right direction (toward innocence).

[EDIT: After reading comments on this post, I have done some updating of my own. I now think I failed to adequately consider the possibility of my own overconfidence. This was pretty stupid of me, since it meant that the focus was taken away from the actual arguments in this post, and basically toward the issue of whether 0.001 can possibly be a rational estimate for anything you read about on the Internet. The qualitative reasoning of this post, of course, stands. Also, the focus of my accusations of irrationality was not primarily the LW community as reflected in my previous post; I actually think we did a pretty good job of coming to the right conclusion given the information provided -- and as others have noted, the levelheadedness with which we did so was impressive.]

For most frequenters of this forum, where many of us regularly speak in terms of trying to save the human species from various global catastrophic risks, a case like this may not seem to have very many grand implications, beyond serving as yet another example of how basic principles of rationality such as Occam's Razor are incredibly difficult for people to grasp on an intuitive level. But it does catch the attention of someone like me, who takes an interest in less-commonly-thought-about forms of human suffering.

The next time I find myself discussing the "hard problem of consciousness", thinking in vivid detail about the spectrum of human experience and wondering what it's like to be a bat, I am going to remember -- whether I say so or not -- that there is most definitely something it's like to be Amanda Knox in the moments following the announcement of that verdict: when you've just learned that, instead of heading back home to celebrate Christmas with your family as you had hoped, you will be spending the next decade or two -- your twenties and thirties -- in a prison cell in a foreign country. When your deceased friend's relatives are watching with satisfaction as you are led, sobbing and wailing with desperation, to a van which will transport you back to that cell. (Ever thought about what that ride must be like?) 

While we're busy eliminating hunger, disease, and death itself, I hope we can also find the time, somewhere along the way, to get rid of that, too.

I'll conclude with this: the noted mathematician Serge Lang was in the habit of giving his students "Huntington tests" -- named in reference to his controversy with political scientist Samuel Huntington, whose entrance into the U.S. National Academy of Sciences Lang waged a successful campaign to block on the grounds of Huntington's insufficient scientific rigor.

The purpose of the Huntington test, in Lang's words, was to see if the students could "tell a fact from a hole in the ground".

I'm thinking of adopting a similar practice, and calling my version the Amanda Knox Test. 

Postscript: If you agree with me, and are also the sort of person who enjoys purchasing warm fuzzies separately from your utilons, you might consider donating to Amanda's defense fund, to help out her financially devastated family. Of course, if you browse the site, you may feel your (prior) estimate of her guilt taking some hits; personally, that's okay with me.

Comments (632)

Comment author: Seth_Goldin 08 September 2016 04:46:54PM 2 points [-]

For those interested, Netflix has a new documentary out about the case: https://youtu.be/9r8LG_lCbac

Comment author: [deleted] 30 August 2015 08:43:28AM 0 points [-]

This article should be our pitch to non-rationalists.

Comment author: JohnBonaccorsi 03 February 2014 09:23:00AM *  2 points [-]

Dear fellow-poster Desrtopa --

Something called a "karma problem" has prevented me from replying directly to your comment at 03 February 2014 08:52:06AM. In the hope you will spot it, my reply will be posted here. I'm afraid it's the last comment I'll have time for; your reply to it, should you choose to post one, will be the last word in our exchange.

Suppose that you were living in a rather more paranoid country, where the government suspected you of subversive activities. So, they took a current captive suspect, tortured them, and told them they'd stop if the suspect accused you. If the suspect caved, would you blame them for accusing you, or the government for making them do it?

I would hope my friends would know I would applaud their doing anything--even torturing me--to avoid being tortured themselves. That goes double for strangers.

PS At 02 February 2014 11:49:15PM, I wrote, with respect to Knox's accusation of Lumumba: "The utterance of such a false thing, outside, maybe, a literal torture chamber, is depraved." I withdraw the word "maybe."

PPS Let's consider your own personal experience, the stressful interrogation you underwent about the money you were suspected of taking. Were you tortured? Was Knox tortured? If Knox was of the view that she was tortured, she had a duty--not merely to herself but to everyone--to take the stand in her trial and say her story-changing and her accusation of Lumumba were products of torture.

Comment author: JohnBonaccorsi 05 February 2014 04:01:17AM 12 points [-]

Reply to myself:

I hereby withdraw every negative thing I have said about Amanda Knox at this website. In the period since I posted the comment immediately above, I could not drive from my mind a remark my fellow-poster Desrtopa made in a post at 03 February 2014 07:39:06AM. In effect, Desrtopa asked whether I would fault a person for giving changed-stories because of torture; if I wouldn't, why would I fault the person for giving changed-stories under interrogation so harsh that its effect on the person being questioned would be tantamount to that of torture? At the time, I avoided answering Desrtopa's question.

Just a few minutes ago, I read commentary by a "veteran FBI agent" named Steve Moore. The commentary was posted at http://www.injusticeinperugia.org/FBI7.html , which is a page of a website called Injustice in Perugia. Having known really nothing about interrogation before I read Moore's remarks--and having had no sense how a law-enforcement professional would evaluate various types of interrogation--I had no right to remark on Amanda Knox's performance under interrogation in this case. Moore's remarks have persuaded me of what Desrtopa was, in effect, asking me to consider, namely, that the interrogation of Knox was a disgrace. Moore's closing paragraph was as follows:

"This is an innocent college girl subjected to the most aggressive and heinous interrogation techniques the police could utilize (yet not leave marks.) She became confused, she empathized with her captors, she doubted herself in some ways, but in the end her strength of character and her unshakable knowledge of her innocence carried her through. It’s time that the real criminals were prosecuted."

In saying "the real criminals," Moore seems to have been speaking of the interrogators themselves. If that is, indeed, what he meant, I would say he used the right term.

Should the conviction of Amanda Knox be upheld, and should Italy request Knox's extradition from the United States, the U.S. government, I hope, will decline to extradite her. The U.S., in my estimation, should do much more that that to right the wrongs that have been done in this matter.

Comment author: komponisto 05 February 2014 05:24:52AM 6 points [-]

Congratulations on changing your mind!

You did it exactly right: you realized you lacked knowledge in a certain domain (interrogation, in this case), proceeded to learn something about it, and updated your previous opinions based on the information you received.

Less Wrong exists pretty much in order to help people become better at doing exactly that.

My hat is off to you, sir.

Comment author: JohnBonaccorsi 05 February 2014 06:30:31AM 3 points [-]

Thank you, komponisto. Congratulations to you on this fine essay. I think I must have first encountered it in December 2012, when I first learned of Less Wrong and came to see what the site was. Though I didn't do much to absorb the essay at that time, it stayed in my mind; the news the other day about Knox's re-conviction moved me to read it again. My mental process in response to that rereading has, in a sense, been recorded here, in my last few days' worth of exchanges with Less Wrong posters. When I posted my first comment in response to the essay, I wasn't sure it would be noticed, because the essay was more than four years old. Fortunately for me, Less Wrong's participants were paying attention.

Comment author: JohnBonaccorsi 02 February 2014 09:29:59PM 0 points [-]

Within the last twenty-four hours, I think, I posted here a comment that has been removed--unless my browser is not displaying the page properly. The comment was a reply--an addendum--to my own comment of 31 January 2014 09:33:17PM. Going by memory, I'll say it read as follows:

Having pursued, over the past twenty-four hours or so, some information about the case, I would say that, whether she was involved in the murder, Knox is a catastrophic failure of personality formation, one who, at the least, increased the agony of Kercher's family by making an understanding of the murder forever impossible. Sympathy for her is as much of a menace as she is.

If the comment has, in fact, been removed, the party who removed it will kindly tell me why. If it was objected to on the ground that it did not address the probability of guilt of Knox, Sollecito, or Guede, I'm not sure the removal was fair. Komponisto's essay to which the comments here are a response is itself not quite limited to that probability question. It expresses and, in a sense, advocates sympathy for Knox and thus opens the door, as a lawyer might say, for a comment such as the one I posted.

Comment author: V_V 02 February 2014 10:13:41PM 1 point [-]

It hasn't been removed.
When a comment score becomes lower than a certain threshold, the forum auto-collapses it and its subthread. You can still read it by clicking on the [+] button on the right.

Comment author: JohnBonaccorsi 02 February 2014 10:25:33PM 1 point [-]

Got it. Thank you.

Comment author: joaolkf 01 February 2014 02:29:55AM 0 points [-]

I am sorry to ask since it looks like a great post, but could you kindly point me to the bit you actually do the math/reasoning about the estimatives?

Comment author: christopherj 31 January 2014 03:13:49AM 0 points [-]

Whoops, looks like Amanda Knox is guilty again. Of course, the lack of double jeapordy protection in Italy might be an impediment to their extradition request.

Comment author: wedrifid 31 January 2014 07:40:45PM 2 points [-]

Whoops, looks like Amanda Knox is guilty again.

This is an area in which word use is important. "Is guilty" is not a fact about the universe or Amanda Knox that is changed by the behaviour now of corrupt Italian prosecutors.

Of course, the lack of double jeapordy protection in Italy might be an impediment to their extradition request.

"Innocent until proven guilty. And also innocent after proven guilty then proven not-actually-proven-guilty. Like, innocent for keeps."

Comment author: komponisto 31 January 2014 08:10:52PM 0 points [-]

Just to expand on your point:

"And also innocent after proven guilty then proven not-actually-proven-guilty.."

should probably be "...innocent after proven 'guilty'...", lest we lose the meaning of "proven".

Comment author: wedrifid 31 January 2014 08:50:07PM *  0 points [-]

should probably be "...innocent after proven 'guilty'...", lest we lose the meaning of "proven".

Good point. I also feel the urge to put quotes around 'proven' for the same reason, distinguishing the epistemic act from the political victory.

Comment author: shokwave 31 January 2014 04:10:28AM 1 point [-]

It better be.

Comment author: wedrifid 04 April 2013 09:05:35AM 0 points [-]

I have heard that the acquittal of Amanda Knox has been overturned. The sources I have found have mentioned the possibility that Knox could be extradited from the US back to Italy and don't rule that out as a possibility. I am hoping someone with an interest in the Knox case (Komponisto) or someone familiar with US laws could tell me whether that is a possibility.

This is relevant to me since simply labeling Italy as a corrupt state that I wouldn't ever visit costs very little (I have no particular reason to visit Italy). However if Knox is (or even could be) extradited from the USA then that is a problem with the legal system of the United States of America, not just of Italy. The USA is a place I may consider returning to so isn't so easily written off. The prospect of extradition means visiting a country carries all the risks of flaws in that country's legal system as well as all flaws in any country with which it has extradition treaties (subject to whatever filtering the details of those treaties entail).

I am also interested in whether the criticism of the wikipedia coverage is accurate. Wikipedia is a source that I frequently rely on for information. Anything which should increase or decrease the amount of trust I place in wikipedia as a source is useful to me.

Comment author: V_V 03 February 2014 12:35:25AM *  2 points [-]

This is relevant to me since simply labeling Italy as a corrupt state that I wouldn't ever visit costs very little (I have no particular reason to visit Italy). However if Knox is (or even could be) extradited from the USA then that is a problem with the legal system of the United States of America, not just of Italy. The USA is a place I may consider returning to so isn't so easily written off. The prospect of extradition means visiting a country carries all the risks of flaws in that country's legal system as well as all flaws in any country with which it has extradition treaties (subject to whatever filtering the details of those treaties entail).

Isn't that a bit of an overreaction?

I mean, no matter how bad this miscarriage of justice seems to be, the probability of being wrongly convicted of murder while visiting Italy is low, certainly much lower than the probability of being hit by a car.
But being extradited to Italy while visiting the US for a wrong conviction of murder, even if you have never visited Italy before? Probably less likely than being hit by a meteoroid.

Comment author: wedrifid 03 February 2014 05:50:15AM 3 points [-]

Isn't that a bit of an overreaction?

I decline to go to Italy based on this and the other research it prompted. The nature of a power structure I am exposing myself to has significance to me even when I am relatively confident in my ability to keep myself self safe. For the same reason I would be unlikely to make a tourist visit a counter-factual USA which still kept all black people enslaved. I'm white so am unlikely to be enslaved but I would still hold what I see in contempt.

the probability of being wrongly convicted of murder while visiting Italy is low, certainly much lower than the probability of being hit by a car.

The information gained about the culture of Italy by the acceptance of ongoing public corruption is not limited to making predictions specific to whether I personally will be falsely convicted of murder.

Comment author: V_V 03 February 2014 11:10:33AM 0 points [-]

So you are not going to visit Italy, and possibly the US, as a form of political protest?

Comment author: wedrifid 03 February 2014 03:37:30PM 0 points [-]

So you are not going to visit Italy, and possibly the US, as a form of political protest?

That is not what I said. (I am departing this conversation.)

Comment author: TimS 04 April 2013 02:39:47PM 2 points [-]

Briefly, the Italians would have to request extradition. If they did, the US would hold a hearing to determine if there was sufficient evidence to extradite. The standard at that hearing is roughly "Is P(guilty) > .25 ?"

Here is a news / opinion article that suggests the Italians are unlikely to ask for extradition, and the standard for extradition probably could not be met. It sounds basically right.

Comment author: Kevin 04 April 2013 10:00:20AM 1 point [-]

It's a possibility, I think, but it would be a very political issue if it happened, and I would expect the US Department of State to intervene to prevent it.

Comment author: AlexSchell 04 October 2011 12:41:19AM 0 points [-]

This might not be seen by many, but it might make your day to hear that Amanda Knox has just been acquitted.

Comment author: Dreaded_Anomaly 03 October 2011 08:13:22PM 17 points [-]

Amanda Knox acquitted.

Justice is finally served.

Comment author: private_messaging 31 January 2014 09:58:40AM *  3 points [-]

Overturned, though.

With regards to "bayesian" analysis in question, as dilaudid said, the fact that a body was found makes for a fairly high probability that one out of a fairly small number of people connected to the victim has committed or participated in the murder. Even more so for a staged break-in.

The reason why we shouldn't imprison people based on things such as apparently weird behaviour has little to do with it's impact on probability, and everything to do with the potential for the abuses that a subjective criterion would create, as well as discrimination against "weird people" such as borderline autistic. We have to think what is going to happen on the bigger scale if we start using "weirdness" as evidence in the court.

The issue in this case is that the narrative presented by the police seems incredibly improbable even given all the facts, and there are far more probable narratives where she committed a lesser crime (such as being an accessory after the act). People who would commit murder are much rarer than people who may act as an accessory.

Comment author: MarkusRamikin 05 October 2011 07:15:20AM *  4 points [-]

That took a while.

BTW, it just struck me, why do we tend to talk about Amanda Knox and fail to mention Rafaelle Sollecito?

Comment author: Desrtopa 05 October 2011 10:57:42PM 7 points [-]

Amanda Knox is American, so she gets more attention from American news media.

Comment author: JoshuaZ 05 October 2011 11:37:23PM 1 point [-]

And a white female. Don't forget that part.

Comment author: MarkusRamikin 06 October 2011 05:56:40AM 4 points [-]

And easier to type out.

Comment author: wedrifid 05 October 2011 08:15:16AM 3 points [-]

Mostly because she is more attractive.

Comment author: gwern 03 October 2011 09:48:23PM *  2 points [-]

Thanks for the link; I've updated both predictions on PB.com.

Comment author: APMason 03 October 2011 08:20:05PM 9 points [-]

Or at least injustice has stopped being served.

Comment author: beoShaffer 29 June 2011 07:18:48PM 4 points [-]
Comment author: JimS 20 June 2011 02:34:20AM 10 points [-]

Measuring cellphone call times down to "3 seconds" is meaningless. Mobile-to-mobile call setup times over the cellular network can easily be 4-5 seconds or more. While the network is trying to find the phone you called guess what ... you hear ringing on your phone even though a connection hasn't been set up. So it wouldn't be unusual for the caller to hear 5-6 seconds of ringing before the called phone starts ringing. 3 seconds of ringing on the called phone could easily translate into 6-9 seconds of ringing on the calling phone.

In the US, I prefer to hang up before the voice mail prompt. It leaves a missed call message and makes it easier for the called party. But when in Italy, better let the phone ring until voice mail just in case the called party died ....

Comment author: MarkusRamikin 16 June 2011 12:38:54PM *  9 points [-]

I've wanted to reply here for a good while, so now that I've finally emerged from Lurkdom, I might as well do that. Great post!

Think about what you're doing here: you are invoking the hypothesis that Amanda Knox is guilty of murder in order to explain the fact that she hung up the phone after three seconds.

That was beautiful. Probably the single most important sentence in that whole article, at least in terms of convincing me to your reasoning.

I have to say though, at least one thing you say sounds not just overconfident but blatantly partisan:

known to have had utterly benign dispositions prior to these events".

I wonder how you could know this. If you picked it up from any pro-Knox source of information, it strikes me as a safe assumption that such a source would paint the defendants as angels regardless of the truth.

I'd also like to ask, how necessary to your argument was using that Jesus example? That's preaching to a very narrow choir, even considerably narrower than just "atheists". If that's what you wanted then no problem, but I'm thinking about the lost potential of this article to be persuasive to a more general public. This would be a great article to link friends to if it didn't rely on, not just the tools of rationality, but on specific conclusions shared by (I presume) most lesswrongians.

Comment author: komponisto 16 June 2011 02:46:48PM 1 point [-]

I've wanted to reply here for a good while, so now that I've finally emerged from Lurkdom, I might as well do that. Great post!

Thank you! Though I would probably write it differently today, it remains my favorite post, in the sense that upvotes and positive feedback on it make me happier than on anything else I've written here.

known to have had utterly benign dispositions prior to these events".

I wonder how you could know this. If you picked it up from any pro-Knox source of information, it strikes me as a safe assumption that such a source would paint the defendants as angels regardless of the truth.

Perhaps, but remember that this isn't something like a political issue, where there are always advocacy websites on both sides. Very few defendants X even have "pro-X sources of information" to begin with -- even if they're privileged (which is not particularly the case of Knox, by American standards). And even when they do, it's often because the case has (or is perceived to have) political implications, and the support is politically-themed. In my view, availability bias resulting from hearing a lot about those types of cases results in an underestimation of the evidentiary value of advocacy on behalf of a defendant like Amanda Knox.

But, remember in any case that we have plenty of anti-Knox advocacy to contrast it with, in addition to the numerous media sources (now including several books) that attempt to be more "neutral" (though often fail). And there just isn't anything bad that anyone can actually find, despite many people trying really hard. The best the anti-Knox folks can do is to come up with their own highly sinister, distorted interpretations of Knox's and Sollecito's personalities, not shared by anyone who actually knows either of them. The absence of objectively negative anecdotes is conspicuous. Meanwhile there are all kinds of good things that have been said about both defendants by people who know them.

I'd also like to ask, how necessary to your argument was using that Jesus example?

Not necessary at all; it was indeed basically an applause light for this particular audience. Of course, there wasn't anything actually wrong about it. And the point I made with it was important: social consensus can't be trusted, or at any rate is very easily screened off.

But yes, the post was definitely targeted specifically at Less Wrong readers, as opposed to the general public. Though I've been surprised at how little negative reaction there has been from outsiders on account of the swipes I took at religion -- virtually none, in fact. The main barrier is a general unfamiliarity with the LW culture of Bayesianism -- but since this post was designed to be a specific application of the LW perspective, I'm not sure how much that could have been helped.

Comment author: [deleted] 16 June 2011 10:04:42AM 2 points [-]

This post is a year and a half old now, but I think this is still worth saying:

"But come on," says a voice in your head. "Does this really sound like the behavior of an innocent person?"

You have to shut that voice out. Ruthlessly. Because it has no way of knowing. That voice is designed to assess the motivations of members of an ancestral hunter-gather band. At best, it may have the ability to distinguish the correct murderer from between 2 and 100 possibilities -- 6 or 7 bits of inferential power on the absolute best of days. That may have worked in hunter-gatherer times, before more-closely-causally-linked physical evidence could hope to be evaluated. (Or maybe not -- but at least it got the genes passed on.)

This type of thing has no place on Less Wrong. You're telling us to ignore an intuition—not just to be skeptical of it, but to ignore it—because of what is, at best, an educated guess about how we evolved. If this intuition really is unreliable, then it ought to be possible to conduct some sort of experiment showing that it's unreliable. Until we see such an experiment, the best way to proceed is not by ignoring these intuitions, but by mere skepticism.

Comment author: komponisto 16 June 2011 11:03:27AM *  8 points [-]

This type of thing has no place on Less Wrong. You're telling us to ignore an intuition—not just to be skeptical of it, but to ignore it—because of what is, at best, an educated guess about how we evolved.

This is not correct. I'm not telling you to ignore it; I'm telling you that it's worth no more than a few bits of evidence -- few enough to be swamped into unnoticeability by the other data in this context. And, as far as I know, the idea that we evolved in small bands has more than enough scientific support to be taken as a given.

"This type of thing has no place on Less Wrong" is far too harsh, even if you disagree. (It reminds me of "entirely wrong".) Do you have any important disagreement with me about the relative strengths of the evidence under discussion here?

Comment author: [deleted] 16 June 2011 11:53:57AM 0 points [-]

This is not correct. I'm not telling you to ignore it; I'm telling you that it's worth no more than a few bits of evidence -- few enough to be swamped into unnoticeability by the other data in this context.

Well, would you agree that the phrase "shut that voice out, ruthlessly" could plausibly be interpreted as meaning "ignore that intuition entirely"? That was how I first interpreted it. Perhaps your post should be rephrased, so it's more clear that "shut that voice out, ruthlessly" actually means "recognize that that intuition is contradicted and outweighed by the other evidence".

If that is what you meant, then I agree with this part of your assessment.

"This type of thing has no place on Less Wrong" is far too harsh, even if you disagree.

Well, I do believe that we should not advise people to ignore their intuitions outright, unless we have a very strong argument for doing so. Naturally, this is irrelevant if you are not advising people to ignore their intuitions outright.

Comment author: MarkusRamikin 16 June 2011 01:32:13PM 5 points [-]

Part of it appears to be Komponisto's style: the post is peppered with things like "completely", "utterly" "nothing", "ruthlessly", "gigantic".

However, I think "shut that voice out, ruthlessly" may be pretty good advice at least at some point in the thinking/decision process. Because even after you've taken everything (including that voice) into account, and concluded that the true answer is different than it "feels", and the intuition you feel is the result of an identified bias, your right answer might still "feel" wrong. The bias will keep injecting doubt, and it takes effort to shake it off. It's hard to get a heuristic to admit it when it's leading you astray. ;)

Comment author: komponisto 16 June 2011 01:27:01PM 2 points [-]

Well, would you agree that the phrase "shut that voice out, ruthlessly" could plausibly be interpreted as meaning "ignore that intuition entirely"?

Tabooing "ignore", I do not think "that intuition constitutes literally zero Bayesian evidence of guilt" is a reasonable interpretation of my phrase. "Your analysis of this case should be for all practical purposes the same as it would be if you didn't have that intuition" is more accurate (where "practical purposes" include things like deciding whether to regard Knox and Sollecito as "innocent" or "guilty", and how strong a level of rhetoric to permit oneself in expressing one's conclusion).

I think it is clear that this post is not about how to distinguish between the kind of extremely small differences in confidence levels that would be entailed by correctly factoring that intuition into one's calculation. Remember that the entire context here is a catastrophic failure of epistemic rationality -- with horrible consequences -- that resulted from people paying too much attention to these types of intuitions. They would have done much better to literally ignore it entirely. (If it actually raises the probability of guilt from 0.001 to 0.002, it would have been better for the police or jurors to have ignored it entirely and estimated 0.001 than to have taken it into account and estimated 0.99, as they effectively did, or 0.5+, as many others have done.)

Comment author: bigjeff5 02 March 2011 06:33:25PM 3 points [-]

I'm ashamed to say I failed this one, and badly.

I'm new to the Way of Bayes, and I've been reading the sequences regularly (that's why I'm on this post, actually) and thinking I've been doing pretty well, but this illustrates that I have a long, long way to go.

I did do a whole lot better than the jury in this case, such that I would never have convicted Knox and her boyfriend, but I still came away with about a 60% probability of their having been guilty, with Guede at >95%.

I started with the pro-guilty website, and thinking back I clearly privileged their hypothesis. In fact I had only assigned about an 80% probability that they were guilty after reading their evidence, which would not have been enough to convict. They made scant mention of how little DNA evidence was actually used to convict them (even calling the braw-clasp significant, damning evidence), and they certainly didn't compare this to the massive amounts of DNA evidence found for Guede. In fact they made it sound as though the evidence was equivalent.

I then updated based on the pro-defense website, down to 60%, a clear case of anchoring. Had I considered the defense's evidence from a fresh perspective there is no way I could have come away with the estimate I did. The overwhelming DNA evidence against Guide should have relegated all other evidence to almost negligible importance. Everything else was unreliable, and I did not treat it as such even though in my mind I even thought that it was unreliable.

A good analogy for the DNA evidence compared to everything else would be like trying to star-gaze at high noon - the light from the sun overwhelms the starlight because the starlight is far, far too weak. Likewise the circumstantial evidence was far too weak to be of any importance when compared to the DNA evidence.

Comment author: komponisto 04 March 2011 03:57:58AM 1 point [-]

I'm ashamed to say I failed this one, and badly...this illustrates that I have a long, long way to go.

On the other hand, you'd be surprised at how difficult it is for people to understand this even after seeing the explanation. While of course it's always preferable to get things right on the first try, the fact that you saw it so clearly after reading this post places you in a high percentile for learning speed.

(I know whereof I speak here, because I've spent some time arguing about this in other parts of the internet, only to be dismayed by the true extent of people's ability to clack. Heck, even here in the comments section of this post there are some pretty confused comments with depressingly high scores.)

I think your analysis is excellent, and is an admirable example of "cognitive debugging". This part in particular is worth dwelling on:

Everything else was unreliable, and I did not treat it as such even though in my mind I even thought that it was unreliable.

It is really difficult for people to discount information, and to actually update on evidence of the form "that information may not be reliable", rather than treating it as an "opposing argument" to be rationalized away, or simply forgetting it altogether. Something like the bra clasp provides an example of this: people hear about it, and decide that Sollecito is guilty. Then, when they hear the defense argue that it's unreliable, they mentally dismiss it as "the defense trying to poke holes in the prosecution's case". They may respect the social obligation to provide some sort of answer to the defense's arguments, but they don't consider that the defense arguments should actually impact their belief about whether Sollecito is guilty; the belief-formation process was over and done with at the first stage!

It's not that they explicitly, consciously think like this, of course; rather, they have just failed to fully incorporate the "rules" into their unconscious belief-generating system. The third and fourth virtues are hard.

I like the star-gazing-at-noon analogy, and may use it myself in the future.

Comment author: bigjeff5 04 March 2011 05:07:27AM 2 points [-]

I think your analysis is excellent, and is an admirable example of "cognitive debugging". This part in particular is worth dwelling on:

Everything else was unreliable, and I did not treat it as such even though in my mind I even thought that it was unreliable.

That's what upset me the most. I made a special note of it, in order to give it a very low weighting, yet it was still a major factor in my assessment. It had to be, because the prosecution's case hinged on it.

I think next time I notice something like that I will have to assign it a specific weight as soon as I decide that it should be given a low weight. Instead I just labeled it as "weak" in my head and moved on.

So when I think "that's likely true" I should stop and consider what the actual number is that I would assign to it. This would help considering in spotting cases where I assign more than 100% total probability to an outcome. If I am thinking it is 70% likely that they are guilty and 60% likely that they aren't, there is an obvious problem. If I don't assign any numbers until I'm finished looking at the problem then I'll never spot this error, as I'll simply calculate not-guilty likelihood from the guilty likelihood.

Much to think about and much to learn still.

Comment author: Seth_Goldin 11 June 2010 03:03:19AM 4 points [-]

I know this is an old thread, but for any people just now reading it, I thought I'd pass along this bizarre development.

Comment author: komponisto 11 June 2010 04:29:54AM 2 points [-]

See discussion here.

Comment author: michellesings 26 April 2010 06:54:53AM 0 points [-]

Your first paragraph was enough for me to halt. Consider the source. If what the internet is saying is more correct than what the Italians were told and innocently believe, as did I, then it's no waste of time at all. Some of the people on the internet are whack, some have studies hours and hours and hours with an open mind.

Comment author: Seth_Goldin 24 March 2010 03:23:41AM *  3 points [-]

I'm a little late to this game, but I spent over an hour, maybe two, comparing the information from the two websites. I had known nothing previously about the case.

My answers: 1: 0.05; 2: 0.05; 3: 0.95; 4: 0.65

So, I feel pretty vindicated. This was a great complement to Kaj Sotala's post on Bayesianism. With his post in mind, as I was considering this case, I assigned probabilities to the existence of an orgy gone wrong as against one rape and murder from one person. There is strong Bayesian evidence for Guédé's guilt, but it's exceedingly weak for Sollecito and Knox. This has really helped the idea of Bayesianism "click" for me.

komponisto, your reasoning is wonderfully thorough and sound. I can corroborate that I deliberately found myself "shutting the voice out" concerning the activity with the mop. You have a great explanation, overall. These two posts of yours are in the running for my all-time favorites.

Comment author: komponisto 25 March 2010 05:53:30AM *  7 points [-]

Thanks for the kind words!

Actually, looking back, I now think I could have done better. In particular, I wish I had been more explicit about the central probability-theoretic point: the fact that the evidence against Guede screens off Kercher's death as evidence against Knox and Sollecito. This point was missed by a number of commenters; if you read the discussion you'll find various people saying that the prior probability "should" take into account the fact that a murder occurred in Knox's house. In actuality, of course, it doesn't matter where you start, so long as you eventually incorporate all of the relevant information; but what must be understood is that if you start with probability mass assigned to Knox and Sollecito because of Kercher's death, then you have to take (most of) that probability mass away upon learning of the evidence against Guede. In other words, under this setup, evidence of Guede's guilt becomes evidence of Knox's and Sollecito's innocence -- something which is counterintuitive and very easy to forget (with tragic consequences).

This issue of "choosing the prior" and other Bayesian subtleties encountered in these discussions may be worth revisiting at some point.

Comment author: redlizard 17 August 2013 12:32:40AM *  1 point [-]

In particular, I wish I had been more explicit about the central probability-theoretic point: the fact that the evidence against Guede screens off Kercher's death as evidence against Knox and Sollecito.

I think this insight warrants a great amount of emphasis. The fact that Kercher's death is screened off by some factor unrelated to Knox and Sollecito means that the question of whether the given evidence against Knox and Sollecito is sufficient to judge them co-conspirators is equivalent to the question of whether the given evidence against them would have been sufficient to judge them murder-conspirators in the absence of a body. And I don't think anyone believes THAT is the case.

Comment author: imgleader 06 March 2010 03:46:44PM 2 points [-]

I have a strong preference for the pragmatism of Occam's razor. If William of Occam had been the Knox case prosecutor it would have never come to trial. When supporting negative cultural stereotypes (i.e. promiscuity of American college girls) becomes more important than a rational outcome results like the Knox verdict arise as the judge overlooks evidence to punish the stereotype instead of the defendant.

Comment author: imgleader 06 March 2010 03:34:41PM 0 points [-]

Made a claim that verdict used Bayesian inference and then failed to support it . It also overlooked elements of the verdict were composed of complete supposition that had no supporting evidence

Comment author: komponisto 19 February 2010 02:17:02AM 5 points [-]

(Beginning thread for a debate with Rolf Nelson. Others also welcome to comment, of course.)

Okay, Rolf, so to get things started, I'd like to get your numbers out on the table. So, if you wouldn't mind, please tell me, first of all, your current posterior probability estimates for the guilt of:

  1. Amanda Knox
  2. Raffaele Sollecito
  3. Rudy Guede

(I expect we'll mainly focus on Knox and Sollecito, since that's obviously where our main disagreement is; I've included Guede for the sake of comparison.)

Next, I'd like to know your priors for Knox and Sollecito (and Guede as well, if you wish), by which I mean your estimate of the probability that each suspect would commit a crime of this sort, as of (let's say) a month before Kercher's death.

Then, if you could, please list, in descending order of evidentiary strength, the pieces of information most responsible for moving your estimates away from the above priors -- along with, if you wouldn't mind, a rough order-of-magnitude estimate of the strength of each piece of evidence, in terms of likelihood ratios, bits, or bels, whatever you prefer. (Again, I'm most interested in Knox and Sollecito; Guede is optional, at least for now.)

This should allow us to quickly pinpoint our disagreement(s).

Comment author: FAWS 22 February 2010 12:28:48AM *  2 points [-]

Oh, let me play!

(When you made your first post on this issue I found trying to look for unbiased information a terribly frustrating experience so I didn't look for more than 20 minutes, and haven't done any reading on it since, except for a cursory look the the wikipedia page just now. A list of all points that are agreed on by both sides (with sub-points arguing about the relevance of the point from both perspectives, perhaps) would have been very welcome)

Current posterior: not really sure, let's see what I end up with below, but as a starting point:

0.01<P(S) < P(K) <0.2 < 0.8< P (G) < 0.99

Priors for commiting a homicide in a specific month:

P(K)= 4.7 *10^-6 (US homicide rate, assuming being female and a young adult roughly cancel out)

P(S)= 4 *10^-6 (Italian homicide rate assuming young adult males are 4 times as likely to commit murder as average)

P(G)=1*10^-5 (had been implicated in a break-in)

An inhabitant of the top floor of that apartment being murdered in her room in this same specific month (R):

P(R|K)=0.1, P(R|~K)=4.5*10^-6

P(R|S)=0.04, P(R|~S)=4.95*10^-6

P(R|G)=0.0005, P(R|~G)=5*10^-6

Guede's DNA being found all over and inside the victim of a homicide in this same specific month (D_G):

P(DG|K)=1*10^-4, P(DG|~K)=6*10^-7

P(DG|S)=5*10^-5, P(DG|~S)=6*10^-7

P(DG|G)=0.6, P(DG|~G)=1*10^-7

I can't think of any other pieces of evidence that I can treat as effectively independent. Given R and treating the probability of any murders except R as effectively 0: Knox' DNA not being found on the victim (D_K):

P(DK|K)=0.5 P(DK|~K)=0.8

P(DK|S)==0.85 P(DK|~S)=0.81

P(DK|G)=0.82 P(DK|~G)=0.82

Sollecito's DNA being found on bra clasp of the the victim, but nowhere else (D_S):

P(DS|K)=0.0002 P(DS|~K)=0.00006

P(DS|S)==0.001 P(DS|~S)=0.00005

P(DS|G)=0.00007 P(DS|~G)=0.00007

Minimal trances of R's DNA found on the blade of one of the knifes in Sollecito's kitchen possibly matching one of three wounds, along with Knox' DNA on the handle (D_R):

P(DR|K)=5*10^-6 P(DR|~K)=1*10^-6

P(DR|S)=1*10^-5 P(DR|~S)=1*10^-6

P(DR|G)=1*10^-6 P(DR|~G)=1*10^-6

Trying to calculate the probabilities based on those estimates I find that I shouldn't have treated DG and R as independent either, I get a stupidly high result of 0.9999983 for P(G), and the indirect association with Guede shouldn't make the other two much more likely given that they are already more directly associated with the victim, if anything DG should make them less likely. The background probability for R should be higher because I forgot to properly account for the fact that there was more than 1 possible victim. Since Guede's DNA and being a room mate alone would already be enough to make Knox almost certainly guilty based on the numbers above and this makes no sense whatsoever I think we can safely say I thoroughly failed this test. I guess the lesson is that making up plausible numbers for various conditional probabilities well outside your intuitive range and then applying them in a basian update doesn't improve your calibration if you have no experience at it at all.

Comment author: komponisto 22 February 2010 02:15:28AM 3 points [-]

When you made your first post on this issue I found trying to look for unbiased information a terribly frustrating experience

One of the lessons of this exercise, that may be worth stating explicitly, is that there's no "outside referee" you can look to to make sure your beliefs are correct. In real life, you have to make judgments under uncertainty, using whatever evidence you have.

It's not as hard as you (and others) think. Yes, of course, the sources are "biased" in the sense that they have an incentive to mislead if they can get away with it. But what they say is not literally all the information you have. You also have background knowledge about how the world works. Priors matter. If A says X and B says ~X, and there's no a priori reason to trust one over the other, that doesn't mean you're stuck! It depends on how plausible X is in the first place.

I guess the lesson is that making up plausible numbers for various conditional probabilities well outside your intuitive range and then applying them in a basian update doesn't improve your calibration if you have no experience at it at all.

Here's the real lesson: Bayesian calculations are not some mysterious black-magic technique that you "apply" to a problem. They are supposed to represent the calculations your brain has already made. Probability theory is the mathematics of inference. If you have an opinion on this case, then, ipso facto, your brain has already performed a Bayesian update.

The mistake you made was not making up numbers; it was making up numbers that, as you point out in the end, didn't reflect your actual beliefs.

Comment author: FAWS 22 February 2010 03:11:44AM *  2 points [-]

One of the lessons of this exercise, that may be worth stating explicitly, is that there's no "outside referee" you can look to to make sure your beliefs are correct. In real life, you have to make judgments under uncertainty, using whatever evidence you have.

I meant that questions that should have an easily determinable answer, like "Did someone clean the blood outside her room up before the police was called" were unreasonably difficult to settle. Every site was mixing arguments and conclusions with facts. Sure, it's possible to find the answers if you look long enough, but it's much more work than it should be, and more work than I was willing to invest for a qestion that didn't interest me all that much in the first place.

Here's the real lesson: Bayesian calculations are not some mysterious black-magic technique that you "apply" to a problem. They are supposed to represent the calculations your brain has already made. Probability theory is the mathematics of inference. If you have an opinion on this case, then, ipso facto, your brain has already performed a Bayesian update.

The brain doesn't operate with very small or very big numbers, though. And I doubt it operates with conditional probabilities of the sort used above, as far as it operates Bayesian at all I would guess it's more similar to using venn diagrams.

The mistake you made was not making up numbers; it was making up numbers that, as you point out in the end, didn't reflect your actual beliefs.

The point is that I didn't spot that until after I did the calculation, and while I don't usually do much in the way of statistics I intuitively got the simple Bayesian problems like the usual example with false positives in a medical test right before hearing about Bayes theorem for the first time, so I don't think it's because I'm particularly bad at this. If you need to tweak afterwards anyway doing the Bayesian update explicitly isn't very useful as self-control.

Comment author: AnnaGilmour 21 February 2010 08:12:26PM *  0 points [-]

This should allow us to quickly pinpoint our disagreement(s).

The disagreement most likely stems from the reliability of the Micheli Report for accuracy and comprehensiveness.

Comment author: AnnaGilmour 21 February 2010 08:08:33PM 0 points [-]

Posterior probability estimates:

  1. 0
  2. 0
  3. .9

Priors:

  1. .01
  2. .01
  3. .5

Is that the sort of thing you are asking? I don't know if I attributed correctly.

Comment author: komponisto 21 February 2010 08:22:31PM *  0 points [-]

Anna: for the context of this, see here.

You may want to remember that 0 and 1 are not probabilities. Also, I must say I don't understand your extremely high prior of 0.5 for Guede. (The evidence against him is such that the prior could be much, much lower and he would still have a very high probability of guilt.)

Comment author: AnnaGilmour 23 February 2010 01:52:42AM 2 points [-]

The thing that I am trying to point out is that I believe Amanda and Raffaele were wrongly included in the class called "suspects".

Comment author: komponisto 23 February 2010 02:11:41AM 1 point [-]

Yes indeed -- our term for that here is privileging the hypothesis.

Comment author: wedrifid 23 February 2010 02:13:39AM 0 points [-]

(Although I do find the point more salient when it is described explicitly rather than by reference to jargon. )

Comment author: komponisto 23 February 2010 02:34:20AM 1 point [-]

Wasn't trying to enforce the use of jargon so much as classify the fallacy.

After all, the point is even more salient when you can relate it to a whole category of error found in many other contexts.

Comment author: AnnaGilmour 23 February 2010 04:44:10AM *  1 point [-]

I find the term useful. I think it is what a lot of the media has done. Since Amanda and Raffaele are in discussion and named in the theory, there must be something to it and they have equal weights of measure for concern as the third suspect, Rudy. When in fact, they are very lightweight and the (heavy) weight should be attributed to the method by which they became suspects. The term helps me to say "Oh that's what is going on." Like komponisto said, a whole category of error. (Not to mention all the contexts apart from this specific case, the topic at hand, indeed.)

Comment author: komponisto 23 February 2010 05:01:13AM 3 points [-]

Quite right. It's actually amazing how little attention was paid to Rudy Guede in the media coverage of this case, particularly in the U.S. and U.K. media. (Numerous stories either omitted all mention of him altogether or else referred briefly and vaguely to "a third suspect" -- without any hint about the disparity in evidence.)

Comment author: AnnaGilmour 23 February 2010 01:58:36AM 0 points [-]

I am also pointing out that is a question pertaining to applied situation with a limited scope - the decision to convict or exonerate. For all intents and purposes, relative "knowing" is permissible in a legal case, since we are dealing with human events and activities of a finite nature - a court decision is a discrete (not continuous) matter. After a certain point, probabilties have to turn into decisions.

Comment author: AnnaGilmour 23 February 2010 02:02:12AM -2 points [-]

Therefore, I offered 0 in the spirit of Goedel's completeness theorem, yes, at the expense of consistency. Consistency will yield a perpetual motion situation. Completeness is required and can be appropriately reached through reasoning, logic, objectivity, etc. Something can only consistent OR complete. Not both.

Comment author: AnnaGilmour 21 February 2010 08:45:07PM *  0 points [-]

In other words, his psychological profile and actions leading up to the murder do not indicate that he was above board and immune from a violent attack, especially an attack with a knife. He was also known around town to go too far in the direction toward harassment of females around town at the clubs and so forth. He was also known to do various drugs including aggression-increasing drugs such as cocaine. He was known to break and enter and steal, and that he carried a ten inch knife "for protection" (his words). It could be argued then that it was a matter of brief time for him to break and enter, steal, and encounter someone indoors in the process as was arguably such in the situation with Meredith, and "defend" himself when caught or interrupted. This is the case that I would start to make as for a high prior.

Comment author: AnnaGilmour 21 February 2010 08:40:25PM 0 points [-]

It is true that a high probability of a prior is not necessary for probability of guilt.

It is also true, however, that it doesn't mean that he didn't have a high prior. I could drop it to .3 though. With the actions in the previous weeks, a case could be made that he was in an escalating pattern of behavior, which is why I gave him a .5 prior.

Comment author: AnnaGilmour 21 February 2010 08:36:49PM 0 points [-]

Thank you. Yes I've seen the post by Rolf Nelson.

I don't understand (though I admit for expediency's sake did not fully read the 0/1 link which I should do if I post here) how there cannot be an absolute for innocence. I didn't assign 1 to Rudy Guede for the reason you mention. But in terms of innocence, we know for example that Princess Diana didn't kill Meredith and that the mayor of Seattle at the time did not kill Meredith, so how can it not be zero? I wrote zero for a specific reason. I wanted it to indicate that gap between reasonability of arrest and no reasonability of arrest. To assign even a small possibility at this point seems inaccurate to me. Although, you make a good point, in actuality, so I would amend them to .001. Is that a proper probability quotient in terms of the question?

Comment author: komponisto 21 February 2010 08:42:53PM 0 points [-]

Although, you make a good point, in actuality, so I would amend them to .001. Is that a proper probability quotient in terms of the question?

Yes, that would be more reasonable (indeed, it's about where my own estimate is).

Comment author: AnnaGilmour 21 February 2010 11:24:02PM 0 points [-]

Is it possible to show that it would be impossible for them to have been participants making it 0? Is there anyone in the world in that class - of 0? Trying to understand the parameters of "probability".

Comment author: RobinZ 21 February 2010 11:55:35PM 3 points [-]

I agree with Alicorn - a probability of 0 or 1 can only be legitimately used as hyperbole.

(There's a technical explanation for why to exclude probabilities of 0 and 1, but it assumes you have studied and understood Bayes theorem and know how to think about probabilities in real life in Bayes terms.)

Comment author: Alicorn 21 February 2010 11:27:37PM *  3 points [-]

Exactly-0 isn't on the table at all. Close-enough-to-0-that-you-can-represent-it-that-way-without-too-much-disclaiming is reserved for propositions like "a square circle and Batman teamed up to, not kill, but kidnap and replace with a convincing inert android, Meredith". Princess Diana's odds of having killed Meredith are miniscule, but not zero or even compellingly zerolike, compared to those.

Comment author: Jack 22 February 2010 12:23:36AM 1 point [-]

"a square circle".

I don't know if this means I disagree with Eliezer but I'm pretty sure the probability of a contradiction has to be 0 and the probability of a tautology has to be 1. Else really weird things start happening and you can't do deduction. Like, what is the probability of A given A ^ B?

Comment author: wedrifid 22 February 2010 01:17:51AM 0 points [-]

I have also seen Eliezer tempted to consider a '0' probability in response to a 'divide by infinity' situation. (I think there is a 'mathsy' way to represent that kind of '0'.)

Comment author: kpreid 22 February 2010 01:53:09AM 0 points [-]

That's called a limit. What's special is not the “zero” but the “infinity”: you don't talk about a value “infinity” (attempting to have one causes you to lose various other useful properties), but rather that as some input increases without bound, the output approaches zero.

“The limit of 1/x as x approaches infinity is zero."

Comment author: Alicorn 22 February 2010 12:39:55AM 4 points [-]

Something can be metaphysically/logically impossible without it being okay to assign exactly-0 to it. Epistemic probability is what we're really representing here - I mean, even something as uncertain-to-me as the current weather conditions in the red spot on Jupiter is exactly one way. But it's not useful to represent that single-ness of weather conditions because I can't access them. I similarly can't usefully access absolute epistemic certainty about even simple math and logic. I'm a broken machine; I cannot handle perfect surety.

Comment author: Jack 22 February 2010 03:08:53AM 1 point [-]

It isn't that simple. Most of the results we get from Bayes theorem we get by deduction. For example, the Dutch book argument, the most common justification given for Bayesian epistemology in the first place, relies on deduction. So does nearly every other important result we get from Bayes theorem. So when you say to someone: take this evidence and act rationally that may imply that that person not get her deductions wrong. This is why, afaict most Bayesians assume logical omniscience. See here. Apparently there have been attempts to weaken logical omniscience and maybe someone here has one in mind... but I haven't heard it. Obviously it is that case the humans, as a matter of psychological fact can screw up deduction. But this is basically like saying that as a matter of psychological fact humans aren't perfect Bayesian rationalists. The whole theory isn't supposed to be descriptive, it is an ideal to strive toward.

Comment author: RobinZ 22 February 2010 12:32:51AM *  11 points [-]

*cackles evilly and cracks metaphorical knuckles*

The circle is defined as the locus of points an equal distance from a center on a plane. A square is defined as a regular quadrilateral - i.e. a shape with four sides of equal length separated by four angles of equal magnitude. If you allow that "distance" may be generalized to be applicable to other geometries than Euclidean...

...what is the shape of a circle on a chessboard, where "distance" is measured by the number of king-moves?

I believe this is a useful object lesson in the difficulty of constructing properly impossible propositions.

Edited to make the square have four sides, not three. What was I thinking...?

Comment author: Jack 22 February 2010 12:42:34AM *  3 points [-]

And when you superimpose a middle finger onto Reimannian space...

Edit: But upvoted because it is always good to get this reminder.

Comment author: AnnaGilmour 21 February 2010 11:38:00PM 0 points [-]

Well, it is quite fascinating that no one gets a 0 probability. Just to ask, does Meredith get a 0 probability? I will move past understanding the exclusion of 0. I just want to make sure I understand. Anyway, when I say 0, I understand it to mean functionally 0, which is the same as .0000000001, which is also functionally 0, correct? Thank you for you patience.

Comment author: Alicorn 22 February 2010 12:34:53AM 5 points [-]

Meredith could have committed suicide. She's probably more likely to be responsible for the death than Princess Diana. And she's much more likely than the team of Batman-and-square-circle.

Comment author: AnnaGilmour 22 February 2010 01:02:56AM 0 points [-]

Were there any fatal wounds that she could not have inflicted?

Comment author: shuttlt 09 February 2010 05:53:03PM 0 points [-]

How about this:

What are the odds that, given a murder in a shared accomodation, one of the occupants is involved if someone known to one of the occupants is known to be involved, more than one person is known to be involved, and that occupant is found to have a false alibi?

Comment author: AnnaGilmour 21 February 2010 07:30:41PM 1 point [-]

You are making an assumption, one exaggeration, and one statement of belief.

Assumption: More than one person is known to be involved. (Not established.)

Exaggeration: someone known to one of the occupants (He was known to the occupants in the cottage below and only only known of by one the occupants alleged to be involved.)

Belief: found to have a false alibi (There is no proof or acceptable evidence that that occupant has a false alibi.)

The means by which the prosecution set about to establish that more than person was involved is suspect. The means by which a false alibi was established is also suspect. You cannot accept those as viable fact. Something that has been shown in previous comments, if I am not mistaken.

Comment author: komponisto 21 February 2010 07:57:36PM 1 point [-]

Belief: found to have a false alibi (There is no proof or acceptable evidence that that occupant has a false alibi.)

It's worth mentioning that what is meant by "false alibi" in the first place is some trivial memory lapse, such as Sollecito misremembering the time when he was browsing websites, etc.

Comment author: shuttlt 09 February 2010 05:46:37PM -1 points [-]

"If Amanda Knox and Raffaele Sollecito were to be in investigators' thoughts at all, they had to get there via Guédé -- because otherwise the hypothesis (a priori unlikely) of their having had homicidal intent toward Kercher would be entirely superfluous in explaining the chain of events that led to her death." They have fake alibi's, a crime scene they believed had been tampered with to conceal evidence, the whole Lumumba story from Knox and evidence from the body suggesting multiple people were involved in the murder. I'm not sure that these are things it's trivial to assign probabilities to in order to work out the odds of anybody's guilt or innocence.

"The hypotheses of Knox's and Sollecito's guilt are thus seen to be completely unnecessary, doing no explanatory work with respect to Kercher's death. They are nothing but extremely burdensome details." Again, the body appeared to show the work of multiple attackers. Knox and Sollecito had lied about their alibi; Guede appeared to have an alibi for the time the police believed the body was moved. Whoever cleaned up after the murder (which the police believed occurred) clearly made little attempt to hide evidence pointing to Guede.

What are the odds of these events given Amanda being innocent and Amanda being guilty? Can anybody tell within a couple of order of magnitude?

Given a murder in a shared house, what is the a priori probability that somebody from that house was involved? 0.1? 0.01?

Surely you are comparing the combined probability of various events whose individual probability you can only guess at and not all of which you may know, that have complex interdependencies and comparing that number against another number that you don't know with any certainty. The likelihood of being out by a very great margin in such a calculation is large.

Comment author: shuttlt 09 February 2010 05:45:27PM 0 points [-]

"If Amanda Knox and Raffaele Sollecito were to be in investigators' thoughts at all, they had to get there via Guédé -- because otherwise the hypothesis (a priori unlikely) of their having had homicidal intent toward Kercher would be entirely superfluous in explaining the chain of events that led to her death." They have fake alibi's, a crime scene they believed had been tampered with to conceal evidence, the whole Lumumba story from Knox and evidence from the body suggesting multiple people were involved in the murder. I'm not sure that these are things it's trivial to assign probabilities to in order to work out the odds of anybody's guilt or innocence.

"The hypotheses of Knox's and Sollecito's guilt are thus seen to be completely unnecessary, doing no explanatory work with respect to Kercher's death. They are nothing but extremely burdensome details." Again, the body appeared to show the work of multiple attackers. Knox and Sollecito had lied about their alibi; Guede appeared to have an alibi for the time the police believed the body was moved. Whoever cleaned up after the murder (which the police believed occurred) clearly made little attempt to hide evidence pointing to Guede.

What are the odds of these events given Amanda being innocent and Amanda being guilty? Can anybody tell within a couple of order of magnitude?

Given a murder in a shared house, what is the a priori probability that somebody from that house was involved? 0.1? 0.01?

Surely you are comparing the combined probability of various events whose individual probability you can only guess at and not all of which you may know, that have complex interdependencies and comparing that number against another number that you don't know with any certainty. The likelihood of being out by a very great margin in such a calculation is large.

Comment author: komponisto 20 January 2010 02:09:28PM *  3 points [-]

On the "liar" issue, and the implication of Lumumba:

What numerous people (not here, for the most part, but with some exceptions) have been either forgetting or ignoring, almost to the point of obstinacy, is that Knox did not come up with Lumumba's name spontaneously. She and Lumumba had exchanged text messages on the night of the killing; in one of them, Amanda wrote "see you later". Her interrogators questioned her aggressively about this correspondence, clearly with the implication that Lumumba (as well as Amanda herself) might have been involved in the murder. The idea of Lumumba's guilt was planted in her head by the police. Knox's "accusation" of Lumumba amounted to no more than saying "Well, all right, I guess maybe he could have done it."

To "lie" is to make an assertion that one knows to be false. Amanda Knox was unambiguously clear about the fact that her "story" about Lumumba being the killer was a dreamlike vision, not an actual claimed memory. It does not constitute a positive assertion about the state of the world, and thus cannot be a "lie". Now, definitions don't matter, of course; but the point is that the lack of correspondence between this particular account and the actual reality of the situation is not Bayesian evidence of her having wished to deceive police about her state of knowledge (which would in turn be Bayesian evidence of her guilt).

Comment author: shuttlt 09 February 2010 06:32:40PM -2 points [-]

"Knox's "accusation" of Lumumba amounted to no more than saying "Well, all right, I guess maybe he could have done it."" I don't want to cause you to rehash arguments you've had here already. There are so many other pieces of evidence of equal value as her 'lie'. I am aware of the circumstances under which Lumumba was mentioned. At the moment all we can say about the circumstances are that she says she was slapped twice on the back of the head and shouted at, they say they didn't. Perhaps evidence will be produced by one side or another at the slander hearing. It's clear though that she, or possibly her family, has been less than truthful about the length of time she was interrogated for.

As for her statement about Lumumba. She said it in her interview ending at 1:45, she repeated it in her statement finishing at 5:45, she repeated it in the "gift" she wrote the following day. Admittedly it is all couched in the "half remembered dream" language of hers.

"To "lie" is to make an assertion that one knows to be false" True. I think she is lying. I find it very difficult to believe that in hour ever much of the hour and fourty five minutes of questioning remained after they got onto the text message she became so confused that for two weeks until Lumumba's alibi came good she was unsure whether what she had said about having been there and listened to Meredith's screams was a dream or a half remembered truth.

"It does not constitute a positive assertion about the state of the world, and thus cannot be a "lie"." Philosophically I agree with you. I just don't think it was sensible of her to make, and then repeat, statements to the police that one has to defend on the grounds that they are do not consitute positive assertions.

"Now, definitions don't matter, of course; but the point is that the lack of correspondence between this particular account and the actual reality of the situation is not Bayesian evidence of her having wished to deceive police about her state of knowledge (which would in turn be Bayesian evidence of her guilt)." How about the false alibi about the party, and the false alibi of using the computer? How many innocent people get caught in two false alibi's? I'm excluding the alibi where she said she was home all night and he said she went out.

Comment author: adrienm 16 January 2010 01:08:52AM 2 points [-]

Enter a comment here

Komponisto I have read your account and interpretations of the evidence, and am refreshed and somewhat relieved to finally find some sense of perspective regarding the events. I was troubled by the outcome of the trial, in my mind the events as they were presented simply did not correlate together. When events are correctly modelled, all additional evidence reinforces the hypothesis. Your Bayesian analysis brought a perspective to the likelihood of the various evidence aspects. The prosecutors presentation of the facts was full of inconsistencies. In addition perspective was not used in evaluating the various items of evidence against likely events. By creating such a fantastical scenario of an extreme sexual it seems the prosecution managed to distract the jury away from their normal perception of what is likely or otherwise to have happened. Note I am not implying such extreme acts of sexual behaviour are that uncommon, however I believe that amongst 20 year old female exchange students with normal family backgrounds, such extreme sexual practices are so rare as to be nonexistent. If one takes this view point and only then looks for evidence to support an event with such a high degree of improbability, then one needs to look for evidence that supports the claim far beyond that of any reasonable doubt. Certainly the circumstantial evidence presented to date is far too insufficient to outweigh this.

Comment author: bigjeff5 02 March 2011 07:08:02PM 1 point [-]

Worse, there was no physical evidence of a forced sexual orgy, there was no evidence that Knox or Sollecito were interested in such an orgy, there wasn't even any evidence that they had the slightest inclination toward that kind of behavior.

In other words, it was a hypothesis drawn from nothing, created in order to support a larger hypothesis that was based on extremely weak evidence and made before a far more likely guilty party was known.

The massive amounts of evidence pointing to Guide should have made this possibility extremely unlikely, and without it there was absolutely no reason for Knox and Sollecito to be involved at all.

Comment author: komponisto 15 January 2010 08:59:34PM *  5 points [-]

A flurry of more recent comments, (concerning in particular the nature of evidence), plus some private message correspondence, provides me with an excuse to make what are probably somewhat-overdue comments succinctly summarizing the main points of this post, addressing the most important issues and objections raised by others, and tying up some loose Bayesian ends.

Objections raised to my arguments seem to fall mostly into the following categories:

(1) Bayesian pedantry: pointing out that weak evidence is distinct from zero evidence, that rational evidence is distinct from legally admissible evidence, arguing that I chose "the wrong prior" (as opposed to just coming out and accusing me of failing to update on piece of evidence X), etc.

(2) Claims that I am too dismissive of psychological evidence.

(3) Object-level arguments from a few people who (still) think there is a significant chance Knox and Sollecito are guilty.

Here are some general responses, divided up into three separate (threaded) comments for ease of reading (and possibly replying):

(1) Bayesian pedantry.

In the first version of the post, when I wrote "there is for all intents and purposes zero Bayesian evidence that Amanda and Raffaele are guilty", I thought that "for all intents and purposes" was enough of a disclaimer; but really, of course, what I should have written was: "there is for all intents and purposes zero net Bayesian evidence...". Obviously there is some (weak) evidence of K and S's guilt; but (I claim) it is cancelled out by the evidence of their innocence to such an extent that the posterior probability is close to (not necessarily literally equal to) the prior probability.

And yes, by "prior probability", I am entitled to mean the probability that Amanda Knox would commit murder, rather than the probability that Amanda Knox would commit murder given that a murder occurred in her house. I have not neglected to take into account the latter information, and indeed, the fact that her housemate was murdered obviously raises the probability that Knox is guilty of something to a level significantly above the background prior. However, this probability is lowered again by the information that Guede committed the murder -- and this is true despite the fact that evidence of Guede's guilt is not itself evidence of Knox's innocence. As Eliezer put it,

the fact that we know Guede did it means that there's no unexplained murder around for Knox to be convicted of.

The Bayesian structure of this inference is simple enough. Let H be the hypothesis that Knox killed Kercher, and let E be the datum that Kercher was killed. Obviously, H and E are not independent; in fact, H strictly implies E, which means that P(H&E) = P(H). Thus P(H|E) = P(H)/P(E), which is larger than P(H). Now, however, let E be the datum that Kercher was killed by Guede. Then H and E are much closer to being independent, i.e. P(H&E) is only slightly larger than P(H)P(E), which means that P(H|E) is close to P(H)P(E)/P(E) = P(H). As I argued in the post, this is Occam's Razor at work: P(H&E) = P(H)P(E) << P(E).

To those who gasped at my dismissal of the DNA evidence against Knox and Sollecito when it is my solemn Bayesian duty to consider all available information, I would put it that Bayesian rationality is supposed to be more accurate than legal reasoning, not less. The kind of legal rules of evidence that would come into play here exist because of known biases people have toward convicting defendants (others, not relevant here, exist as a reflection of society's willingness to let a few culprits go free in order to maintain a certain incentive structure on police and prosecutors). Thus, if when you put your Bayesian goggles on, you suddenly find that defendants are looking more guilty than they used to, you're probably doing something wrong. In any case, dismissing evidence is not an illegal Bayesian move; it simply constitutes an assertion that the likelihood ratio for the information in question is close to 1. In other words, the evidence is very weak. Which probably has something to do with why it might not be admissible in court.

Comment author: komponisto 15 January 2010 09:01:58PM *  4 points [-]

(2) Claims that I am too dismissive of psychological evidence.

Some folks appear to have misunderstood me as arguing that psychological evidence can be dismissed out of hand by its very nature, or that Amanda Knox shouldn't have been questioned by police despite being Kercher's roommate. Obviously, neither is the case. First of all, psychological evidence, strictly speaking, is physical evidence. In fact, all evidence is physical. The question, always, is about how strong a given piece of evidence is. In the post, I mentioned two rules for this: (i) the closer the spatiotemporal connection, the stronger the evidence -- something which follows from the laws of physics; and (ii) high-prior data is at most weak evidence of a low-prior hypothesis (or: thou shalt not postulate a strange thing to explain a less strange thing) -- an immediate consequence of Bayes' Theorem.

If a person's behavior were sufficiently unusual, it might constitute significant evidence they were involved in a homicide. And if a murder occurs in Knox's house, Knox is clearly one of the first people the police should interview. But the psychological evidence against Knox is in fact very weak: the causal linkage between Knox's cartwheels, phone calls, or speculation about Lumumba's involvement on the one hand, and a hypothetical murder committed by her on the other is very tenuous compared to the causal links between these things and more local factors which are likely to be largely independent of Kercher's murder. And yet, many people mistakenly believe the evidence is strong. Why? Because, for perfectly understandable evolutionary reasons, people are interested in psychology; it's salient in their minds, and they mistake this salience for evidentiary strength. They find it easy to imagine a guilty Amanda Knox doing cartwheels, and caught up in the narrative, forget to properly consider the ways in which an innocent Amanda Knox could also end up doing cartwheels. (In fact cartwheels were never something particularly unusual for Knox.) And, in continuing to consider such weak evidence against Knox after the strongest evidence in the case -- the evidence from Kercher's room -- has pointed decisively to the crime having been committed by Rudy Guede, they compound the error by privileging the hypothesis, or, in other words, overestimating the prior probability, of Knox's guilt.

Comment author: komponisto 15 January 2010 09:05:37PM *  4 points [-]

(3) Object-level arguments from a few people who (still) think there is a significant chance Knox and Sollecito are guilty.

There don't appear to be many LW regulars who assign high probabilities to Knox and Sollecito's guilt. There are a few who remain apprehensive about doubting the rationality of the jury or of people like Judge Micheli (the judge in the Guede case) to the extent of lowering the probability of guilt to single digits of percentage; but mainly, they agree that acquittal is called for. My remarks here will thus be directed mostly at people chancing upon this post from outside.

It is incorrect to assume, as some people have, that because I didn't mention various facts about the case in this post, that I am therefore unacquainted with them. On the contrary. However, I do assert that the essence of the case -- the decisive information -- is just what I presented here. Among my main points was that people have been distracted by various other details to the point of getting the wrong answer. The central case in point would be the eight members of the Perugian jury, who despite hearing all kinds of information over the course of nearly a year, were unable to sort out the clutter from the essential facts, which are these:

  • The prior probability of Knox and Sollecito having committed murder is extremely low; of having committed this particular kind of murder, even lower.

  • Since Guede is unquestionably responsible, the mere fact of Kercher's death does not need to be explained.

  • There is no evidence that Knox was in Kercher's room on the night of the crime, and almost no evidence that Sollecito was.

  • There is almost no evidence of any association between Knox and Guede, still less of any between Sollecito and Guede.

  • There is no evidence of antipathy toward Kercher on the part of Knox or Sollecito, or of any other plausible motive for the crime.

  • Every piece of apparently strong prosecutorial evidence has either been totally discredited or is subject to serious doubt (examples: footprints, "mixed" blood, knife, bra clasp, cleanup,...).

  • The remaining prosecution case consists of odd physical facts that are nowhere near as strange as Knox or Sollecito being guilty (broken window circumstances, apparent rearrangement of scene), dubious psychological inferences (inconsistencies => cover-up, cartwheels => not sad, not sad => guilty), and outright non-sequiturs (Knox named Lumumba & Lumumba innocent => Knox hiding something).

  • Knox and Sollecito (along with Lumumba) were suspects before Guede was; the basic theory of the crime was not revised when Guede was discovered.

The above facts are indisputable; there can be little question about which way the winds of evidence blow in this case. Yes, there are lots more detailed facts you can learn about the case (and I know a bunch of them), but as regards the question of who is guilty and who is not, the above is what you need to know, and the rest is noise.

Comment author: rolf_nelson 01 February 2010 08:41:25PM *  -1 points [-]

Point-by-point:

Given that AK's roommate is dead, a break-in was staged, and the coroner's report showed multiple attackers, the prior on AK being a murderer of Meredith is rather high. On the other hand, if we throw away all known evidence, the prior of AK (or Guede, for that matter) being a murderer of Meredith is less than one in a trillion. I claim the former approach, where you use evidence rather than ignore it when it's inconvenient, is preferable. [Edit: OK, that was too snarky. Let me instead say that you should start with a tighter prior rather than a looser prior where possible; it makes the math more tractable.]

That said, I think our main disagreement is on whether the prosecutorial evidence holds up.

  1. Why do you believe DNA evidence flies around so easily? Quick tests: Do you find your beliefs about DNA match up with how DNA is used to draw conclusions in any other court cases that you're familiar with? Why was RS and the other roommate's DNA not found in more areas? Google any video of a DNA testing lab. Are they wearing hazmat suits and, if not, why aren't the testers contaminating their own samples left and right?

  2. I disagree the five pieces of evidence you listed (footprints, DNA-mixed blood, knife, bra clasp, cleanup) are discredited. I am interested in hearing why you personally believe each of them is not strong evidence. [Edit: if you limit yourself to one item, my order of preference is DNA-mixed blood, then knife, then bra clasp.)]

  3. Outside of those five pieces of evidence, I also think you're being too dismissive of the other pieces of evidence. For example, why is Knox naming Lumumba a non-sequitur?

  4. If the basic theory was that multiple people, including at least one roommate, killed MK, then there was no reason to abandon that basic theory upon discovering Guede.

Am I correct in that one of our disagreements is this:

Observation: AK claimed she saw Lumumba kill Meredith. Lumumba was therefore detained by the police based on her affidavit, but Lumumba turned out to be innocent.

Your conclusion: The presence of this false accusation decreases the probability of AK's guilt (?!) (Because it somehow leads credence to a railroading theory? You may be buying into a false FoA meme that the prosecution merely replaced Lumumba with Guede to save face.)

My conclusion: The presence of this false accusation increases the probability of AK's guilt.

Comment author: Jack 01 February 2010 11:48:53PM 9 points [-]

My ADHD brain lost interest in this after the huge discussion here covered pretty much everything having to do with the trial. And komponisto knows this stuff way better than I do so I'll let him respond. But nearly all of the regulars here looked at the exact same evidence you are bringing up now and nearly all of us eventually concluded that it was more likely than not that AK was innocent. Moreover, I specifically recall discussions of every single point you bring up and I believe every single one was resolved. So you might want to look back at the comments to the original post (the test of your rationality one) before you make komponisto go through all this again.

Since I was heavily involved in the discussion of the Lumumba 'accusation' I'll just add this: If AK and RS cleaned up their own involvement with the crime, but intentionally left the evidence implicating Guede wtf would AK not just accuse him to begin with? It seems likely bordering on obvious that AK was interviewed under duress, that the police had seen her text to Lumumba as implicating evidence and fed her his guilt. As a result, AK either made up or dreamed this bizarre pseudo-memory in which Lumumba was present. Then when Lumumba was cleared and an actual suspect was found they kept AK in their hypothesis so as to not totally embarrass themselves. Indeed, this explanation is one of the few parts of the story where I feel like I can account for every single fact and where no other particularly different explanation makes sense. Even if Knox did kill Kercher I would still assign this kind of story a high probability.

Comment author: SforSingularity 27 December 2009 08:05:16PM 1 point [-]

I had heard about the case casually on the news a few months ago. It was obvious to me that Amanda Knox was innocent. My probability estimate of guilt was around 1%. This makes me one of the few people in reasonably good agreement with Eli's conclusion.

I know almost nothing of the facts of the case.

I only saw a photo of Amanda Knox's face. Girls with cute smiles like that don't brutally murder people. I was horrified to see that among 300 posts on Less Wrong, only two mentioned this, and it was to urge people to ignore the photos. Are they all too PC or something? Have they never read Eckman, or at least Gladwell? Perhaps Less Wrong commenters are distrustful of their instincts to the point of throwing out the baby with the bathwater.

http://www.amandadefensefund.org/Family_Photos.html

Perhaps it is confusing to people that the actual killer is probably a scary looking black guy with a sunken brow. Obviously most scary looking black guys with sunken brows never kill anyone. So that guy's appearance is only very weak evidence of his guilt. But wholesome-looking apple-cheeked college girls don't brutally murder people ever, pretty much. So that is strong evidence of her innocence.

Comment author: Jack 29 December 2009 09:03:34AM 3 points [-]

One of the comments about the photos was mine I believe. I tried to avoid the photos of both Knox and Kercher (though I failed spectacularly). The fact that Knox is pretty and has a cute smile is worth updating on, perhaps. But for me it would be better to be told those facts rather than figure them out by staring at pictures. Millions of years of evolution have made attractive girls my age more bias inducing than just about anything else in my life. For the lonely I imagine the effect is considerably more dramatic. Surely we don't think the men who wrote Knox letters telling her how beautiful they thought she was are seeing things clearly and objectively.

And everyone is programmed to have their protection instincts kick in on the sight of a young, baby- like face (this is why the facial expression of fear resembles the face of a baby).

Comment author: RonnyRaygun 10 January 2010 09:02:49PM *  1 point [-]

Hello, everyone, my first post, and while I'm not sure it will be seen as entirely rational, here it is anyway :)

I don't know if attractive girls of Amanda Knox's age are more bias inducing. I would tend to think that cute faces do make people feel a certain protective, nurturing instinct. I also think, however, that SforSingularity has a point. I haven't seen any evidence to back it up, but I believe it is rare for "cute" girls to commit violent murder without severe provocation. That's not to say it doesn't happen.

From personal observation, it seems that people who look agressive are more likely to be agressive. Would this be due to the balance of testosterone / oestrogen in the womb, throughout childhood and adolescence, and into adulthood? It would be interesting to find out if studies have been done to prove or disprove this theory. Also, I certainly believe that the above assertions appear to be true in the animal kingdom. Agressive looking animals, almost without exception tend to be more agressive predators. We, both as individuals and as a species, are animals so I see no reason why the same shouldn't apply to us.

Finally, I recently read a study concerning the domestication of dogs. Dogs are known to have evolved from wolves (they can still interbreed very sucessfully) and the hypothesis was that humans selected the most docile wolves and bred them, as they would make better companions and would be easier to train.

To test this, a study was carried out on Russian Silver Foxes. For the last fifty years the most docile foxes have been selectively bred. The current generation is now incredibly docile, and actively seeks out human companionship, but more importantly, they look cute (i.e. they bring out a protective, nurturing instinct in their carers), and show little agression towards people or other animals.

Finally, I don't think any of the above has any bearing on the guilt of Amanda Knox. I am still absolutely amazed that a jury could have convicted her and Sollecito guilty based on the evidence provided.

Comment author: DanArmak 10 January 2010 10:24:53PM 0 points [-]

my first post, and while I'm not sure it will be seen as entirely rational [....]

And then:

I haven't seen any evidence to back it up, but I believe [doesn't matter what exactly....]

Belief without evidence - that's irrationality, right there. You may be misunderstanding the meaning of "evidence" - especially as that word is used in this community.

Comment author: Jack 10 January 2010 10:32:46PM 0 points [-]

I assume he means studies or 'scientific' evidence (as if there were some other kind).

Comment author: DanArmak 10 January 2010 10:39:22PM 0 points [-]

The other kind is rational (Bayesian) evidence. That's what most people here mean by unqualified "evidence", I think.

Comment author: Jack 10 January 2010 11:02:36PM 0 points [-]

Scientific evidence is Bayesian evidence, no? I was just implying that I didn't think there was a special category of evidence gathering delimited as 'science'.

Comment author: Technologos 10 January 2010 11:14:37PM 0 points [-]

Best I can tell, Science is just a particularly strong form (/subset) of Bayesian evidence. Since it attempts (when done well) to control for many potentially confounding factors and isolate true likelihoods, we can have more confidence in the strength of the evidence thus obtained than we could from general observations.

Comment author: Jack 10 January 2010 11:28:57PM 0 points [-]

Yeah, though a lot of science is just building localized, domain specific ontologies (here's what kinds of fish there are, here's what kind of stars there are etc.) and I'm not sure this kind of scientific knowledge is much better than observations you or I make routinely. Also, some evidence gathering is every bit as powerful as science (or more so) and yet is rarely counted as a science ( advanced sports statistics or marketing studies for example).

Comment author: Jack 10 January 2010 09:44:39PM 1 point [-]

Welcome! Feel free to introduce yourself here.

Comment author: mattnewport 10 January 2010 09:23:18PM 2 points [-]

From personal observation, it seems that people who look agressive are more likely to be agressive. Would this be due to the balance of testosterone / oestrogen in the womb, throughout childhood and adolescence, and into adulthood? It would be interesting to find out if studies have been done to prove or disprove this theory.

I don't know of any studies specifically on aggression but this recent study found evidence that people are able to make significantly better than chance personality judgements based on a single photograph.

Comment author: ideclarecrockerrules 10 January 2010 09:29:46PM 2 points [-]

Signaling may play a significant role in this.

Comment author: orthonormal 16 January 2010 03:43:54AM 0 points [-]

As may microexpressions and other things of which we're not often consciously aware. This doesn't go to the level of a single photograph, but the (badly-named) truth wizards can "observe a videotape for a few seconds and amazingly they can describe eight details about the person on the tape."

We communicate more than we think.

Comment author: lispalien 25 March 2010 06:22:23AM 0 points [-]

I followed this link, and found the blog of one of the "truth wizards" from the study. She writes about the Amanda Knox case. It seems to entirely focus on Amanda Knox.

Comment author: komponisto 25 March 2010 05:44:06PM *  5 points [-]

This has been mentioned before; I'll reiterate my reaction in more detail here.

First of all, there is very little "Truth Wizard" analysis of Amanda Knox on that blog (whatever one thinks about the strength of such evidence in the first place). There are several posts about the case, but in only one of them does the author actually attempt to apply her own "lie-detecting" skills to Knox. (In particular, the most recent post on the case just consists of the author's commentary on someone else's argument that Knox is a sociopath; contrary to orthonormal, there is no claim by the author that she herself has detected sociopathy.)

The one post where the author does analyze Knox concerns her statement at Guede's trial, of which only audio (not video) is available. (Of Knox's videotaped testimony at her own trial, the author says: "...without hearing the questions asked of Knox, it is impossible to identify if she is lying." -- emphasis added.) Thus, there is no data about facial expression, which is apparently an important component of the author's technique. Hence confidence in this analysis must be presumably be lowered from what it would be if the author were working from a video recording.

But in any case, the reasoning in that post is awful. To the extent the author is skilled in detecting lies, she is obviously not particularly skilled in explaining how she arrives at her conclusions. Here is an example:

Does this make any sense? She couldn't remember because she was tired? It was the middle of the night? Does anyone believe this is a good reason for a lack of all memory? When Amanda is telling us this, a year has passed from the crime, so why doesn't she elaborate more in this statement? Why isn't she setting the record straight for the judge here and now?

The author seems to be expecting Amanda's memory of an incident to improve over time. Now, I'm not an expert on memory, but this is directly contrary to my understanding of how it works. In fact, (to invoke my own memory here) I distinctly recall Eliezer mentioning once that memories are re-created each time we remember something. If this is true, it implies that memories -- even if they become more vivid! -- would become less entangled with reality over time, not more; which is anyway what you would expect from....physics.

Here is another, well, "red flag", concerning Knox's account of being hit on the back of the head by a police officer:

So, what ended up happening was.... the fact that I had been pressured so much, and I was....(sigh), I was hit in the back of the head by one of the police officers...who said she was trying to make me...help me remember the truth.

She was pressured so much that she was hit on the back of the head? Does that make sense? Why does she change "make me" which is a strong statement to "help me", which is much softer? I find this odd. If someone is hitting me on the back of the head, they aren't "helping me" do anything. They are making me forcefully and brutally react. Why aren't her emotional memories matching her story?

The author completely misses the obvious interpretation (in the absence of prejudice), which is that the phrase "make me" reflected Amanda's emotional interpretation of the situation, but that she corrected it to "help me" in order to more accurately recount what the officer(s) actually said!

This kind of shoddy reasoning is, I regret to say, characteristic of the author's (rather limited) discussion of the case. Whatever truth-detecting skills she may possess, I don't think her posts have provided us with very much useful information at all.

Finally, I will point out that the author (who by the way links to True Justice but not to any pro-Knox site) claims not to have made an incorrect judgement in 5 years...and yet now lists this case among her "successes"! Obviously, that's more than a bit problematic. (It should be noted that not only is the appeals process ongoing, but the conviction only intensified the controversy, if anything.)

Comment author: komponisto 16 January 2010 03:58:07PM 0 points [-]

Link (1:44) for those interested in trying the video experiment on themselves in the present context.

For a much more extended sample, see here.

Comment author: komponisto 29 December 2009 07:11:09AM 1 point [-]

My probability estimate of guilt was around 1%. This makes me one of the few people in reasonably good agreement with Eli's conclusion.

As far as I am aware, all we know about EY's number is that it is bounded from above by 15%.

Since the average estimate was 35% (and that was before this post, after reading which some people said they updated downward, and no one said they updated upward), it's fair to say a lot of people were in reasonably good agreement with EY's conclusion.

Perhaps Less Wrong commenters are distrustful of their instincts to the point of throwing out the baby with the bathwater.

I don't know whether SfS's comment is to be taken as attempted satire or not, but I did wonder if a sort of "Spock bias" might result in reluctance to update on the sort of evidence presented here or here. As it turned out, that didn't seem to be so much of an issue here on LW (for all that character assassination of Amanda played a role in the larger public's perception). By far the biggest obstacle to arriving at probability estimates close to mine was that old chestnut: trusting in the fundamental sanity of one's fellow humans. (The jury must have known something we didn't, and surely Judge Micheli knew what he was doing...)

Comment author: Eliezer_Yudkowsky 29 December 2009 08:32:45AM 2 points [-]

The idea was that anything over 15% was wildly unreasonable.

Comment author: Eliezer_Yudkowsky 27 December 2009 08:27:31PM 7 points [-]

Girls with cute smiles like that don't brutally murder people.

[citation needed]

Comment author: gwern 27 December 2009 08:37:34PM 7 points [-]
Comment author: Bo102010 27 December 2009 10:44:33PM *  1 point [-]

Although "unattractive individuals commit more crime in comparison to average-looking ones, and very attractive individuals commit less crime in comparison to those who are average-looking" is evidence for SforSingularity's claim, his comment is absurd enough to be taken as satire.

Comment author: gwern 28 December 2009 12:53:24AM *  9 points [-]

It's clearly absurd to say that pretty girls never murder people. But allowing for the normal hyperbole and inexactitude of conversational English, I don't think that's what SforSingularity means, rather, 'pretty girls are one of the demographic least likely to be responsible for a brutal murder'.

This isn't too unreasonable.

  • First off, the number of murders so ascribable are small: females make up half the population and if we limit pretty to the top 5% or so (a reasonable guess at % for 'pretty enough that a guy will actively note and think "pretty!"'), we're already down to less than 2.5% of the population.
  • Second, women in general commit far fewer violent crimes than men. http://www.ncjrs.gov/html/ojjdp/jjbul2002_10_1/page4.html mentions that for juveniles, at one point, the male:female ratio was 22:1. Let's be conservative and put the young adult ratio at 5:1; now we're down to 0.4%.
  • Third, attractiveness is correlated with IQ, and IQ is well-known to correlate with lower crime rates. (see Wikipedia for a few links; IIRC, WP understates the case but I can't be fashed to dig up the stronger correlations). Let's cut another 10% off the rate, down to 0.36%.
  • Fourthly, attractiveness correlates to higher socioeconomic status through multiple mechanisms, which cuts down violent crime even further. (I don't think I need to adduce any citations for that!)

And so on. I've missed many factors (eg. maybe happier & less stressed people are more attractive, and that too is correlated to less propensity for murder; maybe pretty women have fewer violence-inducing mental diseases and substance abuse habits; etc.). But I've already knocked their murder rate way down. I suspect it has much further to go in a true reckoning.

Does his comment still look satirical to you?

Comment author: DanArmak 28 December 2009 12:33:06PM *  5 points [-]

we limit pretty to the top 5% or so (a reasonable guess at % for 'pretty enough that a guy will actively note and think "pretty!"')

Interesting. When I read "pretty", I thought of a binary division (make guys judge "pretty or not") and I thought it would yield at least 30-40% as pretty. (Possibly much more, but I've a high degree of certainty that at least that much.)

Granted that your test is different than mine, what leads you to your 5% estimate, which looks low to me even with your test?

Comment author: gwern 28 December 2009 02:12:03PM 1 point [-]

Here's one exercise: take your highschool yearbook, open one of the dense pages (with dozens of pics on it), and let your eye drift along the columns with no particular intent (this is hard); how many of the girls will actually catch your attention for being attractive and not for having, say, bizarre & outdated hairstyles? For me, it was less than 1 in 10. (One plain forgets about the bottom 50% and between that and 90% is the 'unoffensive' range.) Considering that my highschool was private and that selection effects were already operating, I have to revise the estimate further down; ~5% seemed good & is a nice round number.

Comment author: Technologos 28 December 2009 03:47:49PM 4 points [-]

For what it's worth, I remember a study on Stanford undergrads with what was essentially speed dating; men suggested their interest in a second date with ~90% of the women they met, and simultaneously their top criterion for that choice was attractiveness. Even granting that they had loose definitions caused by the study, I suspect that under Dan's metric (binary choice) a reasonably large minority might be tagged "pretty."

I also didn't get the impression from the photos on the website that anybody in the Knox case was pretty in the sense that you mean it--I think of your criterion as defining "remarkably pretty" rather than "pretty, if I had to choose," and I'd say you're probably right on <5% being remarkably pretty.

Comment author: Jack 28 December 2009 12:42:21PM *  5 points [-]

30-40% seems reasonable for Knox's age group (early twenties). Something closer to 5-10% seems reasonable for the entire female population. Keep in mind pretty people are almost certainly more visible than the non-pretty (especially if you have high socio-economic status).

Comment author: gwern 01 January 2010 11:20:43PM 1 point [-]

I think 30-40% is unrealistic: something like 20-30% of females in that age group are overweight or obese, leaving 70-80% in an attractive weight bracket; are we really going to call half of those 'pretty'?

It may just be my media-biased high standards, but I don't think I'd call half of all thin young women that.

Comment author: DanArmak 28 December 2009 12:56:36PM 0 points [-]

Right... I was a fool to miss that. You're perfectly right of course.

Which leads us to the question of what "natural category" to put Knox in. Should it be "a pretty woman out of all women" or "a pretty young woman out of all young women"? Or lots of other options, of course. (We use some category the moment we compare her to women and not to all humans.)

But I'm sure this has been discussed, I haven't read all of this subthread...

Comment author: Douglas_Knight 28 December 2009 09:22:41AM 3 points [-]

First off, the number of murders so ascribable are small: females make up half the population and if we limit pretty to the top 5%..., we're already down to less than 2.5% of the population.

That's like saying very few murders are committed by people named Amanda. That's OK, if you're very careful, but you have to, at least, weigh it against the very few murders by people named Rudy. 2-4 are OK, though.

Comment author: gwern 03 April 2013 06:00:51PM 0 points [-]

Reference class tennis. Being an attractive female with a (formerly) well-off family is far more important a reference class than being named Amanda; and the corresponding reference class for Rudy would be being an unattractive man who is a poor African immigrant.

Comment author: Douglas_Knight 03 April 2013 11:44:24PM 1 point [-]

Reread your comment. What is the point of your your first bullet point that pretty girls are rare? That tells you nothing, just as the fact that Amandas are rare tells you nothing. Points 2-4 about the relative propensity to murder are relevant. But I'm explicitly talking about point 1 in isolation.

Comment author: gwern 03 April 2013 11:53:42PM 0 points [-]

What is the point of your your first bullet point that pretty girls are rare? That tells you nothing, just as the fact that Amandas are rare tells you nothing.

Yes, it does. If there is any sort of inverse quasi-linear relationship between prettiness and propensity to murder, as one would expect, we would expect the reduction in murder rates compared to the average to be the largest at the extremes - that is, for rarely pretty girls we will expect rarely large effects.

Comment author: Douglas_Knight 04 April 2013 12:18:20AM 0 points [-]

That's not how you used it in your post. Seriously, just read your post. What do these numbers mean?

Comment author: Bo102010 28 December 2009 01:14:46AM *  1 point [-]

I think the "My probability estimate of guilt was around 1%" bit is probably pretty spot on (for the reasons you state), and not absurd.

I think the "I only saw a photo of Amanda Knox's face. Girls with cute smiles like that don't brutally murder people" and "Perhaps it is confusing to people that the actual killer is probably a scary looking black guy with a sunken brow" bits are absurd-enough-to-be-satire.

Comment author: Alicorn 27 December 2009 08:26:31PM 5 points [-]

Via what mechanism does wholesome appearance and apple-cheekedness correlate with a disinclination to commit murder? For example, does a murderous disposition drain the blood from one's face? Or does having a cute smile prevent people from treating the person in such a way as to engender a murderous disposition from without? I wouldn't be exactly astonished to find a real, strong correlation between looking creepy and being dangerous. But I'd like to know how it works.

Comment author: SforSingularity 01 January 2010 02:28:44PM *  6 points [-]

Think about it in evolutionary terms. Roughly speaking, taking the action of attempting to kill someone is risky. An attractive female body is pretty much a guaranteed win for the genes concerned, so it's pointless taking risks. [Note: I just made this up, it might be wrong, but definitely look for an evo-psych explanation]

This explanation also accounts for the lower violent crime rate amongst women, since women are, from a gene's point of view, a low risk strategy, whereas violence is a risky business: you might win, but then again, you might die.

It would also predict, other things equal, lower crime rates amongst physically attractive men.

Comment author: Quest4Truth 23 December 2009 09:15:56PM 1 point [-]

komponisto - you are a genius. For months I have felt that Amanda and Rafaelle were clearly innocent, but I could not properly rationalize or verbalize my feelings. How could the entire internet be wrong? How could the jury be unanimously wrong? Now I understand. Thank you and I love your blog. As others have noted, this site is the only place I have found cordial and intelligent debate among the opposing viewpoints.

Comment author: gate 23 December 2009 07:58:18AM 2 points [-]

Rudy Guédé's won his appeal. His sentence has been reduced to 16 years -- ten less than Knox and nine less than Sollecito.

Funny world.

I have no opinion on the guilt or innocence of Knox or Sollecito. I've read the biased accounts of the evidence with amazement. I assumed Guédé's guilt was obvious. Kinda speechless over this new twist. While I can imagine someone thinking all parties were equally guilty, I am unable to find any rationale for deeming Guédé less guilty.

Comment author: Feh 24 December 2009 09:04:15AM 2 points [-]

Rudy chose the "fast track" option, which allows for a one third reduction in prison term, and so that's why his sentence was reduced. I don't really understand their system enough to criticize it, but it seems to me that guilty criminals generally would choose the "fast track" option, and get reduced sentences, whereas the innocent generally would choose the full trial, and get full sentences.

Comment author: captcorajus 19 December 2009 03:19:08PM *  9 points [-]

Here's a thought exercise, that for me clears the confusion in this case. Pretend that you don't already know who the suspects are in this case, and are looking at the evidence to try and find one for the first time. You have no preconceived notion as to who killed Kercher.

Your evidence comes in two weeks after the killing and you have a bloody hand print on a pillow, fingerprints elsewhere in the room, saliva DNA outside the victim and skin or saliva DNA inside the victim as well. All of this is of one person, Rudy Guede.

You look up Rudy Guede and you find that in the weeks prior to the murder he was involved in three separate break-ins involving a knife, but was not arrested. When you try to locate him, you find he has fled the country to Germany.

At this point, do Knox and Sollecito even come into this story as anything other than footnotes? There are no interrogations, no cartwheels, no rumors of bleach purchases, no "foxy knoxy", no stories of sex on a train, none of it. The knife in Sollecito's flat, with a minuscule amount of DNA on the blade that doesn't identify Kercher but can't exclude it never enters the scene. Neither does the bra clasp found 47 days later.

Blood drops of the victim found in a co-habituated bathroom with mixed DNA of roommates doesn't seem all that sinister.

For me, this clears up who the guilty party in this case quite nicely, and takes my "feelings" out of the equation.

Comment author: brazil84 19 December 2009 05:19:37PM *  0 points [-]

In fairness, aren't you also starting with some or all of the following pieces of evidence?:

(1) A room in the crime scene apartment has been ransacked but no valuables (which were in plain view) were taken;

(2) A window in that same room has been broken with marks suggesting it was broken from the inside;

(3) the same window is on the second floor and can be seen from the street. Further, there is no obvious reason why a burglar would need to get in through an upper floor;

(4) Bloodstains indicate that the victim died with her bra on and the bra was removed a few hours later; and

(5) When the police arrived at the crime scene apartment, one of the victim's flatmates was standing there with her boyfriend and with a mop and a bucket.

Comment author: Feh 20 December 2009 06:53:57AM 4 points [-]

brazil84's points 1, 2, and 3 are false in my opinion, I have insufficient knowledge about #4 (the allegedly postmortem removed bra) but my reaction is "so what?" and "how does the investigator know the bra wasn't removed post-cut rather than postmortem?"), and here is my take on #5, the mop and bucket...

The allegation that Amanda and Rafael were found with a mop and bucket outside the crime scene apartment is reported on truejustice.org (which has been accused of bias in some of the comments here.) Truejustice.org claims to be paraphrasing a judge's statements about pretrial hearings. This alleged fact apparently did not come up in the actual trial. In the actual trial, Rafael's maid said she found a mop and bucket underneath the sink at his apartment, and said he explained that they had cleaned up some leaked water. The maid testified that there was a clear liquid in the bucket. My wild guess at the truth here is that indeed Amanda and/or Rafael had taken a mop and bucket from Amanda's apartment to Rafael's apartment to clean up a leak, and the maid saw it when she came in the morning (she cleaned around 11:00 on certain days, as I recall.) And then, possibly, and unfortunately for them, Amanda or Rafael brought the mop back to Amanda's apartment shortly before the police arrived. But your guess is as good as mine.

One thing I stumbled across was this comment to a blog:

"There is one simple reason that I believe that Amanda and her boyfriend are both guilty of some involvement in this crime: they were at the apartment the next morning with a bucket of bleach. Please explain away her guilt under this "circumstance.""

I think that's pretty funny, or at least it would be if the freedom of two individuals weren't at stake. No evidence of bleach, by the way.

Comment author: brazil84 20 December 2009 10:50:18AM -1 points [-]

brazil84's points 1, 2, and 3 are false in my opinion

Well, do you agree that one of the residents of the flat stated that (1) she left her room without clothing strewn all over it; and (2) there were valuables in plain view which were not taken?

Do you agree that a second floor window was broken? Do you agree that the same window was visible from the street?

In short, I would like to know exactly where you disagree with the points I raised.

And please don't simply offer explanations for these things based on the evidence in its totality. I raised these points to show that there was physical crime scene evidence which supports reasonable suspicion of Knox and Sollecito.

And then, possibly, and unfortunately for them, Amanda or Rafael brought the mop >back to Amanda's apartment shortly before the police arrived

Again, please keep in mind that I raised these points with respect to the issue of whether there were grounds to suspect Knox and Sollecito based on the crime scene evidence.

If you would like to jump to a discussion of Knox's (and Sollecito's) guilt or innocence based on all the evidence in its totality, that's fine, but in that case we need to consider ALL the evidence, which includes evidence that was subsequently developed against Knox and Sollecito.

Comment author: Feh 24 December 2009 10:12:28AM *  0 points [-]

I agree that truejustice.org reported that one of the residents stated that she left her room without clothing strewn about and that she left valuables in plain sight that were not taken. I fail to see the relevance to Amanda, especially if the valuables were not clearly valuable or were easily traceable (e.g., the valuables could have been jewelry, which the murderer may have believed risky to fence or believed to be worthless costume jewelry.) Cash was taken.

I agree that a second floor window was broken and that there was easy access to said window from the side/trellis. I fail to see the relevance to Amanda.

You are implicitly referencing the glass-on-clothes argument. I am unmoved by this evidence that the window was broken from the inside because:

  1. Glass fragments could wind up on top of clothes even if the window was broken from the outside. The clothes weren't strewn about before the incident, so, if the glass were broken from the outside then the clothes would have been strewn about after the glass fragments were on the floor, allowing fragments to roll up on top of clothes.

  2. The murderer's objective after the crime seems to have been to delay discovery of the body. The murderer went into the bathroom outside the victim's room to clean himself, then went back into the victim's room, locked the door, and exited through the window. Therefore, even if the window was broken from the inside, which I really, really doubt, it makes sense from the murderer's perspective. Amanda and her boyfriend, on the other hand, sped the discovery of the body by calling the police (although, ironically, other police were already on their way.)

  3. I'm kind of assuming the victim had a European style door lock, which can only be locked from inside, rather than American style door lock, which can be locked before exiting. But if it's true that it was a lock-from-inside style lock, then there is something wrong with the prosecutors. The prosecutors implied there was no way to get in or out of this room through the window (which wasn't true, but never mind), so what happened to the criminal in their estimation? Did he teleport out?

Comment author: brazil84 24 December 2009 11:12:10AM 0 points [-]

Cash was taken.

From the room which was ransacked? If so, this would change my assessment of that aspect of the staging issue.

went back into the victim's room, locked the door, and exited through the window. >Therefore, even if the window was broken from the inside

It seems you are under the impression that the ransacking and broken window were in the victim's bedroom. As far as I know, that's incorrect.

Comment author: Jonathan_Graehl 02 February 2010 09:14:04PM 2 points [-]

Regardless of whether a break-in was actually staged (I don't care), have you ever had your home burgled? I have; they took a few dollars worth of laundry quarters in plain sight, rummaged through some random areas (some drawers, shelves, under the bed, and neglected to take anything else, including electronics, cheap jewelry, and a few hundred dollars cash in a desk drawer.

Comment author: brazil84 03 February 2010 12:03:36AM 0 points [-]

Regardless of whether a break-in was actually staged (I don't care), have you ever had your home burgled?

Never (as far as I know).

Comment author: captcorajus 19 December 2009 06:03:54PM *  6 points [-]

1) Actually, Kercher's rent money was missing and Guede's DNA was found in her purse. After her murder he went clubbing and then hopped a train Milan. Where did he get the money to do that? To state there was no robbery doesn't jibe with the evidence. Knox had $2000 in her bank account, and Sollecito's parents are well off. Guede was a known drifter known for his money problems.

2) No, evidence was NOT that window was broke from the inside. The glass was inside the room, and a rock was found. The dispute arises because some glass was below clothing in Filomena's room. However, Filomena was allowed into her room to retrieve personal effects, so the exact placement of clothing is suspect. Furthermore, the building itself is fairly isolated and traffic along the road is minimal.

3) There is a truss next to the window making access relatively easy. An investigator for the defense, dressed in a suite and tie easily scaled it. Rude Guede was an accomplished athlete and basketball player.

4) That's an evaluation of the judge who accepted the prosecutor's contention of the muti person scenario. Scientific testimony at trial contradicts this assertion. In either case, this is evidence open to interpretation. Even if that were true, there is still no evidence that Knox or Sollecito were involved in moving the body! Putting them in the room a SECOND time hours later further creates a logic problem because no evidence of their presence is in the room! What are they, ghosts?? Even if you prove there was more then one assailant, you still have to prove those additional assailants were Knox and Sollecito... which you can't You must UNLEARN what you have learned my friend. ;)

5) No such evidence was presented at trial, and even if it was so, its completely meaningless. How do you get from "a mop and bucket" to "a three way sex crime"? You must have something stronger in addition to the observation for it to have probative value of a crime! If they cleaned the crime scene how did they leave behind Guede's fingerprints and DNA? Either is all there, or its all gone. You can't selectively clean up microscopic evidence... much less with a mop and bucket. Its laughable.

As komponisto stated, it is difficult to be cold in your rational evaluation. You are assigning the mop and bucket a value almost equal to DNA inside the victim when in real comparison they are light years apart in real value.

Comment author: brazil84 19 December 2009 06:15:47PM *  0 points [-]

Hold on a sec: Are we looking at things from the perspective of the initial evidence available to investigators? Or are we looking at all the evidence in its totality?

These are two separate but related questions:

(1) Does the initial evidence offer a reasonable basis to be suspicious of Knox and/or Sollecito?

(2) Does all the evidence in its totality indicate that Knox and Sollecito are guilty?

It seems to me you just jumped from discussing (1) to discussing (2). If you want to do that, fine, but in that case it's not fair for you to ignore later evidence which developed against Knox and Sollecito.

You are assigning the mop and bucket a value almost equal to DNA

I'm not doing that at all. The mop and bucket are one initial piece of evidence which, when combined with other initial pieces of evidence, form a reasonable basis to be suspicious of Knox and Sollecito.

Comment author: captcorajus 19 December 2009 06:30:10PM *  4 points [-]

How is the mop and bucket evidence of a crime??? That's an emotional response, not a rational one. You must prove 1) the mop and bucket was used to clean up a crime scene, and 2) that Knox and Sollecito were the one that did it. No proof of 1 exists, so how can you prove 2?

1) I'm saying that if you follow the evidence, Knox and Sollecito never enter the picture as suspects. I do not assign behavior as evidence of a crime without strong physical evidence to cooberate it. All we have initially are the behaviors.

2) The evidence in totality can't connect them to the crime or Guede. Guede is completely connected by the evidence. So how can you prove guilt?

I'm saying this: If you START with the cold hard evidence, and proceed from there, Knox and Sollecito are NOT suspects. Since they are not suspect, their behavior isn't probative, and everything that follows: "Foxy Knoxy", Vibrators in the bathroom, sex on a train, cartwheels at the police station have 0 value as evidence of a crime. Get it?

I'm time warping. Starting with the evidence to find the people, not starting with the people and then trying to find evidence to implicate them. Its a thought exorcise.