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

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 possibilty that Meredith may have been annoyed at Amanda for bringing home boyfriends and occasionally forgetting to flush the toilet -- 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 improbabilty 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.

(The Associated Press reported that, apparently, Amanda had some trouble going to sleep after the midnight verdict.) 

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: wedrifid 13 December 2009 05:04:03AM *  6 points [-]

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)? That most other people (including most commenters on my last post) are off by no fewer than two?

Your assertion of such a high probability of guilt does not constitute a claim that most other commenters on your last post were off by no fewer than two orders of magnitude. Probability is subjectively objective. There is one correct estimate for you to have given what you know but this is not the same one that others should have. In fact, given that on average the commenters care less about the subject so did less research if they arrived at the same confidence as you then one of you would probably have to be wrong.

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!)

The task isn't to guess your password. The task is to assign probability estimates about the state of their timeline of universe. Their universe does not include the state 'it is <some completely arbitrary high probability> probable that Amanda is innocent'.

ETA: I totally agree with your main contentions and found your post both insightful and extremely well written. It is rare to see such well reasoned essays from people who are emotionally entangled with the topic.

Comment author: komponisto 13 December 2009 05:29:42AM 0 points [-]

Serious nitpicking going on here. The whole point of my post is that from the information provided, one should arrive at probabilities close to what I said.

I don't have appreciably more info than many who participated in my survey, and certainly not more than the jury in Perugia.

Comment author: aausch 13 December 2009 05:57:28AM 0 points [-]

It might have been more useful to ask for confidence intervals around probabilities. Maybe that should become the standard around here?

That way, I imagine people who did not care so much about the topic/do as much research, would have had a way to indicate the fact.

Comment author: wedrifid 13 December 2009 06:39:25AM *  4 points [-]

It might have been more useful to ask for confidence intervals around probabilities. Maybe that should become the standard around here?

No! In this context confidence intervals around the probability have no meaning!

I do agree that adding extra information about confidence is important for things like this. It's just that this isn't a case for which confidence intervals (approximately) work. It would make more sense if the probability was a property of the universe itself, then you could establish bounds on where the 'true probability' lies (as discussed with komponisto).

Comment author: saturn 13 December 2009 08:14:51AM *  1 point [-]

No! In this context confidence intervals around the probability have no meaning!

Why can't they be confidence intervals around the probability after doing [some amount] more research?

Comment author: wedrifid 13 December 2009 08:20:12AM 1 point [-]

Why can't they be confidence intervals around the probability after doing [some amount] more research?

That you can do.

Comment author: Vladimir_Nesov 13 December 2009 09:44:30AM 1 point [-]

Relevant post: Readiness Heuristics

Comment author: Jawaka 13 December 2009 11:30:39AM 0 points [-]

I feel the same way. I set the probabilities to 25 (not G alone) / 75 (G alone) after half an hour of reading, just because I wanted to have room to be more confident after 2 hours of reading.

Comment author: wedrifid 13 December 2009 06:20:10AM *  10 points [-]

Serious nitpicking going on here.

Probability theories and the philosophies thereof are of interest to me and there are a lot of intuitive traps that are easy to fall into.

The whole point of my post is that from the information provided, one should arrive at probabilities close to what I said.

If that is what your point was then I actually disagree with it. I am not comfortable giving odds of 1:999 after looking briefly at two biassed webpages and a wikipedia page that you tell me is fluctuating at the whims of editorial bias. I know damn well I'd be wrong more than once if I did something like that 1,000 times.

Don't forget that "the order, manner, and quantity of browsing will be left up to [them]". It would be quite reasonable for someone to decide to read until a certain level of confidence has been reached. Once you are 99% confident that the poor girl is innocent what do you hope to achieve by marinating yourself in more and more evidence (or, for that matter, the lack of it)?

It would be great if I could go all Liam Neeson and say "if you let her go now, that'll be the end of it. I will not look for you, I will not pursue you. But if you don't, I will look for you, I will find you, and I will kill you." Alas, I do not have any way to efficiently influence the justice system of Victoria or Australia, much less Italy.

(Damn I hate juries. The thought of being at the mercy of a mob of my peers fills me with equal parts fear and outrage. But it isn't my fight. Except in as much as the only path to a justice system I actually trust probably involves FAI.)

Comment author: komponisto 13 December 2009 06:35:18AM 1 point [-]

If that is what your point was then I actually disagree with it. I am not comfortable giving odds of 1:999 after looking briefly at two biassed webpages and a wikipedia page that you tell me is fluctuating at the whims of editorial bias. I know damn well I'd be wrong more than once if I did something like that 1,000 times

What if I tried putting it this way: people underestimate the (potential) power of applying rationality techniques as compared with gathering more raw information. It is sometimes possible to be extremely confident about a proposition after an hour of Internet research, even when people who have spent a year "gathering evidence" seem to disagree shaprly.

Comment author: wedrifid 13 December 2009 06:51:01AM *  2 points [-]

What if I tried putting it this way: people underestimate the (potential) power of applying rationality techniques as compared with gathering more raw information. It is sometimes possible to be extremely confident about a proposition after an hour of Internet research, even when people who have spent a year "gathering evidence" seem to disagree sharply.

Totally agree, and that's a point that you explained convincingly in your post. Just so long as I don't have to quantise 'extremely confident' as 0.999. Although given an hour and also given that the lesswrong.com discussion is now part of 'the Internet', I expect I would break the 0.99 mark at least.

Comment author: Morendil 13 December 2009 09:39:40AM 3 points [-]

How about a Truth Machine ?

Comment author: Blueberry 13 December 2009 06:54:21PM 0 points [-]

Wow. That book is really good. Thanks for linking to it!

Comment author: Morendil 13 December 2009 07:02:49PM 0 points [-]

You might also like The First Immortal by the same author.

Comment author: jpet 14 December 2009 08:05:02AM *  2 points [-]

Serious nitpicking going on here. The whole point of my post is that from the information provided, one should arrive at probabilities close to what I said.

It's not "nitpicking" to calibrate your probabilities correctly. If someone was to answer innocent with probability 0.999, they should be wrong about one time in a thousand.

So what evidence was available to achieve such confidence? No DNA, no bloodstains, no phone calls, no suspects fleeing the country, no testimony. Just a couple of websites. People make stuff up on websites all the time. I wouldn't have assigned .999 probability to the hypothesis that there even was a trial if I hadn't heard of it (glancingly) prior to your post.

[edit: I'm referring only to responders who, like me, based their answer on a quick read of the links you provided. Of course more evidence was available for those who took the time to follow up on it, and they should have had correspondingly higher confidence. I don't think your answer was wrong based on what you knew, but it would have been horribly wrong based on what we knew.]

Comment author: wedrifid 13 December 2009 05:26:48AM 5 points [-]

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).

Yvain! How could you? What did the probabilities do to deserve that kind of abuse? (I strongly assert that averaging the probabilities is not a good way to combine such estimates.)

Comment author: [deleted] 13 December 2009 06:27:28AM 2 points [-]

I wonder what implications this has for the method of choosing priors I came up with that is "ask everybody in the world what they think the priors should be, normalize the invalid ones, and take the average of all of them".

Comment author: ciphergoth 13 December 2009 09:09:55AM 2 points [-]

What would the right thing look like? Averaging the log-odds ratio?

Comment author: dilaudid 13 December 2009 05:33:23PM 1 point [-]

That's what I would do. If one person is almost certain (say 1/(10^10^10)) then the strength of their view would be represented. Of course if anyone gives an irrationally low or high answer, or puts <=0 or >=1, then it overweights their views/blows up.

Comment author: Yvain 13 December 2009 03:01:12PM 3 points [-]

...and why do you assert that? If you have good reasons, I'd like to see a top level post on the subject, since this is my natural response to a bunch of probability estimates given by different people with the same information who are rational enough that I care what they think.

Comment author: badger 13 December 2009 05:51:55PM 3 points [-]

Not a top level post because I don't think I have the definitive say on the matter, but I made an article in the wiki that illustrates why the mean of the log-odds makes more sense.

Unfortunately, the wiki appears to have issues with math right now, so the article has an ugly error message in it. The formula works fine in the Wikipedia sandbox. If anyone knows what is going on or has any other changes, feel free to edit.

Comment author: wedrifid 13 December 2009 09:52:02PM *  1 point [-]

...and why do you assert that?

Somebody with no information does not so effectively counterbalance ten people who can describe the positions of every atom on the planet.

I calculated an example involving 0.99, 0.5, 0.745 and (1-10^20) but then I noticed badger's link beat me to it.

Comment author: wedrifid 13 December 2009 05:34:27AM 13 points [-]

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

Absolutely. I saw the amount of emphasis prosecutors (and 'guilty' advocates) were placing on this sort of crap and immediately updated in favour of innocent. Presenting lots of ridiculous nonsense is evidence that you haven't not anything better.

Comment author: Douglas_Knight 13 December 2009 04:22:53PM 9 points [-]

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

Absolutely. I saw the amount of emphasis prosecutors (and 'guilty' advocates) were placing on this sort of crap and immediately updated in favour of innocent. Presenting lots of ridiculous nonsense is evidence that you haven't not anything better.

What I found most interesting about this exercise is the number of people who made this deduction. It is an error. They are appealing to the public and the jury, whose rationality you impugn. The prosecutors and especially advocacy websites will present (a lot of) this crap regardless of whether they have better evidence. This is normal behavior for prosecutors, just as changing stories, implicating random people, and signing confessions is normal behavior for innocent people. Similarly, differences in tone and organization of the two advocacy sites is pretty much useless.

Comment author: wedrifid 13 December 2009 09:32:42PM 2 points [-]

What I found most interesting about this exercise is the number of people who made this deduction. It is an error.

I am not convinced. The ratio of speaking nonsense to providing relevant evidence is a valid signal even with our less than entirely rational species.

Comment author: Psychohistorian 13 December 2009 06:15:25AM 3 points [-]

Your point about privileging the hypothesis, and the fact that we feel a need to explain away weird facts in order to believe Knox's innocence, is excellent, though it gets rather buried in a very long post.

As far as the probability estimates go, I expect that many people (like me) did two things: erred on the side of underconfidence, and used numbers as conveying a general feeling. Particularly since it's a criminal case, it doesn't take much to disagree with a conviction. If I'd put the odds of Knox's guilt at .95, I'd say she'd been wrongly convicted, as 5% is extremely reasonable doubt - think that if that were our normal standard, we could have hundreds of thousands of totally innocent people imprisoned. So if people are somewhat like me, they probably just picked a low number to show "not guilty" and left it at that.

Of course, this is largely your point: given the evidence, there's really no reason those numbers should too much higher than they are for a random inhabitant of the city, so our willingness to compromise is itself a flaw, though, in this context, a flaw without adverse effect, as we'd still acquit.

Comment author: MendelSchmiedekamp 13 December 2009 06:37:33AM 11 points [-]

there's really no reason those numbers should too much higher than they are for a random inhabitant of the city

Actually simply being in the local social network of the victim should increase the probability of involvement by a significant amount. This would of course be based on population, murder rates, and so on. And likely would also depend on estimates of criminology models for the crime in question.

Comment author: Psychohistorian 13 December 2009 06:21:11AM 5 points [-]

Negligible. No 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 at most.

Suppose it were somehow revealed to you that three people had in fact committed the murder. Would you still maintain that K and S are no more likely to have been involved than anyone else in the relevant reference class? If not, doesn't this suggest that this quoted bit is an overstatement?

That's a genuine question; I haven't fully thought that concept through.

Comment author: komponisto 13 December 2009 06:46:48AM 0 points [-]

Suppose it were somehow revealed to you that three people had in fact committed >the murder. Would you still maintain that K and S are no more likely to have been >involved than anyone else in the relevant reference class?

There is a proximity effect, just as in the actual situation K's probability is slightly raised by the fact that a killing occurred in her house (and S's is in turn raised by his intimacy with K). But the evidence against G utterly destroys her explanatory value, and brings her probability back down to the prior.

If not, doesn't this suggest that this quoted bit is an overstatement?

No, because this is my posterior probability after taking into account the evidence against G.

Comment author: Psychohistorian 13 December 2009 06:58:35AM *  4 points [-]

But the evidence against G utterly destroys her explanatory value, and brings her probability back down to the prior.

This is true in reality, not in my hypothetical. If it were a fact that three people had been involved, as posited, the evidence against G would not explain anyone else away on its own. I'm using a counterfactual to attempt to show that your claim that there's no special evidence of her guilt is false.

You've stated: [A] P(Knox is guilty) = P(Random person from relevant social circle is guilty). It seems to me that [B] P(Knox is guilty; given multiple killers) > P(Random person from relevant social circle is guilty; given multiple killers). Assume [B] is true. The additional specification does not point to K, it only says that people other than G are guilty. Therefore, [A] should be false. So, I'm assuming you would take issue with the truth of [B], or else with my reasoning, and I'd be curious as to how and why either way.

Comment author: komponisto 13 December 2009 07:17:57AM 0 points [-]

[A] is only true given the evidence against G. Not knowing that evidence, we would have P(Knox) > P(random peer) by proximity.

Comment author: magfrump 13 December 2009 08:54:24AM 0 points [-]

the issue at stake is P(multiple killers) being very small, and P(knox guilty) - P(random person guilty) is less than zero due to the P(G guilty).

Or at least that is how I would weight them.

Comment author: Unknowns 13 December 2009 10:30:12AM 1 point [-]

Given that someone was killed, the probability of multiple killers is not "very small", according to statistics. Definitely not more than 50% but definitely substantial (as I stated in another comment.)

Comment author: Unknowns 13 December 2009 08:06:09AM 1 point [-]

The percentage of murder cases that involve multiple murderers is relevant to the idea that the evidence against G "brings her probability back down to the prior," and this percentage is much higher than you think it is (i.e. it is higher than 1% of cases, and this is enough that AK's probability will definitely not go back to the prior. In fact it seems to be in 10-20% of cases),

Comment author: komponisto 14 December 2009 07:37:34AM 1 point [-]

This is accounted for in my updated estimates.

Comment author: Unknowns 14 December 2009 07:59:15AM 0 points [-]

Ok, but given your updated estimates, it is consequently unreasonable to just dismiss psychological and interpreted physical evidence (i.e. bloody footprints, crime scene rearrangement and so on). Whether this is actually so or not, it is very possible that these things could add together to give enough evidence to say that someone is probably guilty; going from a 1% to a 99% chance does not take an extremely large amount of evidence.

And this seems to imply that an hour on the internet does NOT beat a year in the courtroom. To know whether this is true or not you would actually have to know the evidence in more detail. For example it does seem that even in Judge Micheli's report there is a good deal of detail that has been generally unreported in English.

Comment author: komponisto 14 December 2009 08:07:26AM 1 point [-]

Ok, but given your updated estimates, it is consequently unreasonable to just dismiss psychological and interpreted physical evidence

I don't see why this kind of stuff is any more powerful than its counterparts on the other side: K & S's benign personalities, lack of criminal history, lack of motive, etc.

Comment author: Unknowns 14 December 2009 08:15:07AM 0 points [-]

That may be true. I read (I didn't pay attention to the source, it could be just a rumor for all I know) that AK sent an email to a friend, shortly after coming to Italy, saying that she had convinced a stranger to have sex with her on a train. If true that would show a dangerous kind of behavior, even though not criminal. Assuming she might be guilty (for the sake of argument) the most likely explanation would be that they were "playing around" and things got out of hand, not that anyone ever was planning to murder someone.

In any case it seems my last point stands: the evidence as it has been presented to us may be unpersuasive but that doesn't mean that the same kinds of evidence couldn't become persuasive in principle, and this may be exactly what happened in the trial.

Comment author: rmattbill 15 December 2009 12:39:39AM 3 points [-]

That may be true, but many cases of wrongful conviction involve multiple innocent defendants. The Norfolk Four is a perfect example. At one point the police suspected SEVEN men of the attack, even though the coroner said there was only evidence of an attack by one person. In the end, it turned out one person, a known rapist, had committed the crime, but not before four of the innocent served over a decade in prison.

For those who criticize Knox pointing the finger at Lumumba, again, look at the Norfolk Four case where the first suspect, innocent, wrongfully accused a friend, who then wrongfully accused several friends, who then wrongfully accused several of their friends! It might be impossible to understand the mindset that leads to something as wrong as falsely accusing someone else, but it's happened to a lot of people, and normally they are treated with far less scorn than has been poured on Knox by her critics.

Comment author: AndrewKemendo 13 December 2009 06:43:20AM *  1 point [-]

The most important of which is: if you only do what feels epistemically "natural" all the time, you're going to be, well, wrong.

Then why do I see the term "intuitive" used around here so much?

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.

Hmm, I was told here by another lw user that the best thing humans have to truth is consensus.

Somewhere there is a disconnect between your post and much of the consensus, at least in practice, of LW users.

Comment author: D_Alex 13 December 2009 06:54:17AM 8 points [-]

@OP: you have appealed to rationality in examining this case... then you come up with this:

"1. Negligible. No 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 at most. "

The FACTS include 1) the police came to "her house" and discovered a murder victim in one bedroom and 2) she was tried and convicted. You seem to have given these zero weighting in your final calculation.

And this:

"3. About as high as the other two numbers are low. 0.999 as a (probably weak) lower bound."

Did your prior of "0.001 at most" apply to Guede as well?

I offer $50 to the AK defense fund if you can produce a defensible Bayesian probabilities calculation showing how you got from your priors to your final probabilities. A condition is that you must account for the fact that most (let us say 80% for the purposes of your calculation) persons convicted of a crime in a democratic society are in fact guilty of it, and that you use generally defensible assumptions.

Should you try to do so, Less Wrong readers can decide if you have succeeded by voting on the post containing your calculation.

D. Alex

Comment author: Blueberry 13 December 2009 07:21:50AM 3 points [-]

A condition is that you must account for the fact that most (let us say 80% for the purposes of your calculation) persons convicted of a crime in a democratic society are in fact guilty of it

I'm curious where in the world you get this "fact". I don't believe that at all (and it seems essentially unverifiable). Also, remember that Knox isn't a random person convicted of a crime: most of them don't make international news. Also, Italy does not have the same rights and freedoms as the US: for instance, they don't have separation of church and state.

Comment author: D_Alex 13 December 2009 07:32:40AM 1 point [-]
Comment author: Blueberry 13 December 2009 07:46:00AM 0 points [-]

Thanks for that link. I don't understand why the plea bargain rate is at all relevant. Prosecutors try to dispose of most cases through plea bargaining, and paying a fine may be cheaper than paying legal costs for many people who plead guilty. I don't see any reason why an innocent person would be any less likely to plead guilty.

The innocence project focuses on high-profile murder and rape cases where DNA evidence can be obtained, so it's very non-representative of the criminal justice system as a whole.

Also, this ignores the question of legal justifications and excuses, and other defenses like illegally obtained evidence. If, as a matter of fact, you killed someone, but the evidence was obtained illegally, and you're still found guilty of murder, that's still a wrongful conviction.

Comment author: D_Alex 13 December 2009 07:56:14AM 1 point [-]

The part relevant to my earlier post was:

"....even if juries get it right only 80 percent of the time (an assumption at which most sensible scholars would cringe).... But the real wrongful conviction rate is almost certainly lower, and significantly so ... ".

Comment author: ciphergoth 13 December 2009 09:14:39AM 2 points [-]

The only test I can imagine is: when a new technique, like DNA testing, comes along, test a random sample of cases to which it is applicable. Unfortunately the cases re-examined are very carefully chosen, so no such information is available.

Comment author: [deleted] 13 December 2009 07:30:18AM 4 points [-]

While I have a sort of vague sense of disagreement with this comment, I voted it up, because I would be very interested in an example of Bayesian reasoning applied to the real world without having a truckload of given probabilities to work with. In particular, I don't know how one would take into account D_Alex's 80% while also taking into account more specific factors.

Comment author: Tyrrell_McAllister 13 December 2009 05:13:11PM 5 points [-]

I had the same reaction. I'm strongly inclined toward the OP's position, but if you're going to excoriate everyone else for failing to "jettison [their] intuitive feelings in favor of cold, hard, abstract calculation", you should provide the actual cold, hard, abstract calculations supporting your own position.

Comment author: retired_phlebotomist 13 December 2009 05:05:29PM 1 point [-]

"I offer $50 to the AK defense fund..."

Has the offer been amended from $50,000 to $50 since last night, or did I just misread it at 1:00 AM?

A shame, because I was looking forward to seeing the attempt.

Comment author: [deleted] 13 December 2009 07:13:01AM 0 points [-]

. . . 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.

Hey, now, don't confuse rationality with intelligence. Imagine the world as consisting of spiked pits and gold coins. Rationality is about not walking into spiked pits, and following any pit-free path you find that leads to a gold coin. Intelligence is about actually finding a path leading to a gold coin. Naturally, in order to safely arrive at a gold coin, you need to both find a path and follow it, and the processes need to be intertwined; nevertheless, they are separate processes.

At least, that's the viewpoint that my experiences and intuitions have produced. I've often found myself having the subgoal of creating Friendly AI myself (and, in my defense, checking with Eliezer or someone before running it!), and Friendliness has always seemed more a matter of avoiding spiked pits than of actually finding gold coins.

I find myself needing to go into more detail about my thoughts than I was planning a couple of minutes ago. I've always hoped that we could build a Friendly AI out of two parts: a base built out of rationality, and then intelligence on top. The rationality base would prevent failures of Friendliness but be flexible enough to let rational actions shine through. Nevertheless, it would be very Neat and sound and pretty much immutable. The intelligence-on-top, on the other hand, could be Scruffy and ad-hoc, since it's going to go through loads of rapid modification anyway.

We have managed to come up with one perfect formal system of rationality: mathematics, in which you can be "absolutely certain" of a statement, as long as it can be expressed in a certain language and doesn't actually depend on any observations. We have also managed to come up with another perfect formal system of rationality: Bayesian reasoning, in which you can assign a probability to any statement whatsoever, and be completely correct, as long as you don't mind having to do an infinite amount of computation. Can we find a third perfect formal system of rationality, one in which you can still assign a probability to any statement, in which you don't end up strongly believing falsehoods more often than you should, in which Aumann's agreement theorem holds, in which you can be considered rational, in which you nevertheless don't have to perform an unreasonable amount of computation?

(Wow, this post has gone far from its original point.)

Comment author: Sebastian_Hagen 13 December 2009 07:11:11PM 3 points [-]

We have managed to come up with one perfect formal system of rationality: mathematics, in which you can be "absolutely certain" of a statement, as long as it can be expressed in a certain language and doesn't actually depend on any observations.

That's incorrect. As shown by Gödel's second incompleteness theorem, mathematical formal systems divide into three categories:

  1. Systems that are inconsistent.
  2. Systems that can't prove their own consistency.
  3. Systems that aren't particularly powerful.

When doing math, humans tend to assume that certain formal systems are consistent. But we can't actually prove it; it's ultimately an empirical question (and actually it would be even without the incompleteness theorem; if strong consistent formal system could prove their own consistency, that wouldn't make them any different from strong inconsistent formal systems).

Though as far as empirical questions go, the consistency of certain formal systems fundamental to human math does seem to be extremely probable.

Comment author: Blueberry 13 December 2009 07:16:33AM *  5 points [-]

these two things constituting so far as I know the entirety of the physical "evidence" against the couple

I'd like to know your reaction to this argument. There is some other evidence against the "lone wolf" theory and pointing more towards Amanda, specifically that Meredith's bra was removed and the scene rearranged after her death (and not by Rudy), the bloody footprints that match Amanda, and the witness placing all three of them together near the house around the time of Meredith's death.

(Edited to fix formatting)

Comment author: Jawaka 13 December 2009 11:03:26AM 0 points [-]

Have you read the counterarguments from "Friends of Amanda"?

Comment author: Blueberry 13 December 2009 06:56:04PM 1 point [-]

I looked at that site but I didn't see specific counterarguments addressing that point.

Comment author: komponisto 14 December 2009 07:34:46AM 0 points [-]

Does this kind of evidence have anywhere near 30 bits of inferential power?

To me, it seems more like on approximately the same order as psychological evidence.

Comment author: Unknowns 13 December 2009 07:43:26AM 12 points [-]

You're even more overconfident than Eliezer. Even he didn't say that the probability of guilt should be less than 10%.

Also, you ignored the evidence of the scene being rearranged. As far as I can tell, there was substantial evidence of this, and substantial evidence of it being by someone other than RG. This implies substantial evidence that someone else was involved. Even if this doesn't necessarily imply AK is guilty, it definitely implies a probability higher than the original prior (which itself would be much, much higher than the probability you assign of 1 in a 100,000, given the proximity of the persons).

Basically, you are overconfident if you assign less than 10% chance of guilt. And the fact that your opinion is much more extreme than anyone else's doesn't show that you are more rational, but is very strong Bayesian evidence of overconfidence bias on your part, since it is well known that humans are naturally overconfident, not underconfident.

Comment author: magfrump 13 December 2009 08:57:56AM 2 points [-]

The Friends of Amanda site clearly stated that there was no evidence of cleanup and that "cleanup" had only been referenced in passing in the trial, and the prosecution did not pursue the point.

That is, there is not "substantial evidence" of the scene being rearranged, I'm not sure where you're getting that.

Comment author: Unknowns 13 December 2009 10:24:43AM 2 points [-]

Yes, it made that claim, but as far as I can see it was wrong. Among other things, the bloodstains on her bra and her body indicated that her bra was removed some time after her death. Even by itself, this implies someone rearranging things. Likewise, luminaled footprints, whether or not they were Amanda's and Sollecito's as claimed, proves that someone cleaned something.

Comment author: kodos96 14 December 2009 06:00:01PM 4 points [-]

"luminaled footprints, whether or not they were Amanda's and Sollecito's as claimed, proves that someone cleaned something"

No it doen't. Luminal doesn't reveal blood EXCLUSIVELY. I read somewhere, sorry, can't remember where, that it can also light up things like just sweaty/dirty footprints, no blood necessary.

Comment author: rmattbill 15 December 2009 07:27:15AM 7 points [-]

You're absolutely correct. Not only that, but the Luminol footprints specifically tested NEGATIVE for the presence of blood. Every single one of them.

Comment author: brazil84 13 December 2009 02:11:14PM 2 points [-]

"Also, you ignored the evidence of the scene being rearranged. As far as I can tell, there was substantial evidence of this, and substantial evidence of it being by someone other than RG."

I agree. And also substantial evidence that someone was trying to make it look as though the crime was done by an outsider.

Comment author: brazil84 13 December 2009 10:44:50AM 2 points [-]

For what it's worth, I would have been much more inclined to agree with you before I became a practicing attorney. Having practiced law for many years, I've had many opportunities to assess a case based on hearing one (sometimes 2) sides of the story and then to learn a lot more about the case through the discovery process and then the trial process.

In short, I have a lot of practice in assessing peoples' guilt or innocence and I'm pretty confident that Amanda Knox was involved in the murder of her roommate.

Comment author: Jack 13 December 2009 12:00:49PM 6 points [-]

Can you make explicit your intuitions? What experiences in particular lead you to think this?

Comment author: brazil84 13 December 2009 12:37:20PM *  1 point [-]

Well I've learned as an attorney that in general when people engage in a big or concerted effort to conceal, destroy, or manipulate evidence it's usually because the evidence is (or is perceived to be) damaging to their interests. Here, it seems pretty clear that Amanda Knox staged a break-in to her residence. Why would she do that if she were not involved in the murder?

At a minimum, she must have known before the police came that her roommate had met with serious misfortune. And how would she have known that if she had not been involved in the murder?

Similarly, it seems pretty clear that Knox attempted to manufacture an alibi by spinning a web of lies. Which is difficult to do nowadays since there are various electronic forms of evidence (cell phone records, internet records, etc.) to catch you up, which appears to be what happened.

I suppose it's possible she did all of this because she was innocent but still afraid the police would put the blame on her. But that doesn't make much sense since she could have easily pointed the finger at the African.

Comment author: Jack 13 December 2009 03:31:01PM *  5 points [-]

I'm pretty sure everyone agrees that if it is the case that Knox staged a break-in, knew before the police came that something happened to her roommate or tried to manufacture an alibi by spinning a web of lies then she is likely guilty. And we probably don't need experience as attorneys to tell us that. The question is whether or not the evidence in favor of those things outweighs the absence of physical evidence or any motive, and the fact that female college students don't commit many sexually motivated throat slittings. What evidence for the former exists and how that evidence should be interpreted doesn't appear to be a settled matter. At this point I'm not clear on what was misinformation and what wasn't. But even if a break-in was staged we have no particular evidence tying Knox to the staging. And the so-called "web of lies" is hard to distinguish from the tale of a scared and confused girl abused by police. She must have known something bad had happened to her roommate? This is big news to a lot of us, explain.

Comment author: Unknowns 13 December 2009 03:35:40PM 1 point [-]

The only evidence we have that she was abused by police are Amanda's own statements, which were also contradicted by the police. Given the multiple contradictions in her stories, her claims about the police might or might not be true, but are certainly not strong evidence of anything at all.

Comment author: Alicorn 13 December 2009 03:40:49PM *  7 points [-]

What are the circumstances under which we might expect the police to admit to abuse? I doubt their lack of confession there is strong evidence for anything either.

Comment author: Jack 13 December 2009 03:53:20PM 7 points [-]

This is one reason why police record interrogations, to avoid people making false accusations of coercion to get out of confessions. Alas, first we were told the tape had gone missing. And then later told no tape had been made at all! We don't even have a transcript of the interrogation, just a signed statement Knox obviously didn't write herself. It really is a shame they lost the tape, er, I mean, that no tape was ever made. Then the Italian police could show the world that she was lying all along!

</sarcasm>... You're right of course that Knox isn't reliable. But coerced false confessions are fairly routine as I understand it and the police have every incentive to lie.

Comment author: Unknowns 13 December 2009 04:06:28PM 0 points [-]

In this case, much of the "coerced false confession" was independently corroborated by other witnesses and evidence, while her original alibi was proven false (i.e. by computer and cell phone records.) This would tend to support the police. Although I agree with Alicorn there there isn't much strong evidence either way in regard to how the police treated her.

Comment author: Jack 13 December 2009 04:44:03PM 6 points [-]

The false confession consisted of Knox's semi-hallucinated memory of her boss killing Kercher... who couldn't possible have done it. The police coerced that particular confession because they saw Knox's text message to him. That fact alone is enough to render the interrogation suspect. I don't recall reading that Knox confessed details which could reliably be confirmed independently. But I may have missed that.

Comment author: Unknowns 13 December 2009 05:42:51PM 0 points [-]

http://www.truejustice.org/ee/index.php?/tjmk/comments/our_take_on_the_case_for_the_prosecution_4_amanda_knoxs_multiple_conflictin/

This link suggests that she testified to some things that were independently confirmed. Even regarding the confession about her boss, there doesn't seem to be much evidence that this testimony was coerced (although it was surely untrue.)

Comment author: AnnaGilmour 15 December 2009 04:36:23PM 2 points [-]

Her alibi was not proven false. Where did you read that her alibli was proven false? Just curious.

Comment author: AnnaGilmour 15 December 2009 04:35:21PM 3 points [-]

Other evidence of mistreatment are Raffaele's and Patrick's prior statements of similar treatment. They said it before the defamation claim by the police, which by the way, was made much time after the incident and was the day before the closing arguments by the defense.

Comment author: brazil84 13 December 2009 03:55:27PM *  4 points [-]

"I'm pretty sure everyone agrees that if it is the case that Knox staged a break-in, knew before the police came that something happened to her roommate or tried to manufacture an alibi by spinning a web of lies then she is likely guilty."

I'm not sure if that's true, since the original poster did not really address the staging issue. There is a lot of evidence one can consider, and each of us can make our own judgment about what evidence is more important and what evidence is less important.

Anyway, let's break things down a bit, since your 3 "ifs" are not logically independent.

  1. Do you agree that if Amanda Knox staged a break-in, then she was probably involved in the murder?

  2. Do you agree that the evidence does in fact suggest that a break-in was staged?

  3. Do you agree that if a break-in was staged, the likely perpetrator (of the staged break-in) was somebody who had lawful access to the residence?

Comment author: Jack 13 December 2009 04:37:57PM 1 point [-]

1, Yes. 2. Whoever was in there appears to have made some effort to make things look like a burglary (that is the best explanation for the strewn clothes and the fact that nothing was missing). But that doesn't mean the window breaking was staged. I find the argument that the window as inaccessible and that the glass was on top of the clothing unpersuasive. I don't know if forensics got good photos of the glass, how much there was or if we're just relying on the word of the roommate. 3. If the window breaking was staged then it was likely done by someone with lawful access- that could be Knox, someone with Knox's key, Sallecito, Guede invited up by Kercher, one of Kercher's friends, the landlord etc.

Comment author: brazil84 13 December 2009 09:40:33PM 0 points [-]

I'm a little confused by your answer to number 2. It sounds like you basically agree that somebody tried to stage a break-in. No?

Comment author: Jack 14 December 2009 01:23:54AM 0 points [-]

Someone staged a burglary. It isn't necessarily the case that the broken window is part of a staged burglary rather then a way some intruder actually got in. Perhaps the murderer came in through the broken window but knew the victim and thought that making it look like a burglary would send the police in another direction.

Comment author: brazil84 14 December 2009 02:31:03AM *  1 point [-]

Well that's an important point. As others and I have mentioned, there is a small universe of people who would have had much incentive to stage a burglary. And that universe includes Amanda Knox and her boyfriend.

(Further, without knowing anything more, Kercher's roommate(s) would be the strongest suspects of such a staging. Because (1) only a roommate wouldn't have to worry about another resident showing up and discovering him or her; and (2) a roommate would have the strongest incentive to try to point the police somewhere else. For example, if a casual acquaintance broke in through the window and murdered Kercher, what would that person have to gain by staging a burglary? In effect, they've already engaged in a burglary anyway.)

Anyway, if somebody from that limited universe of suspects is hiding something and can't account for his whereabouts at the time of the murder, it's pretty likely that they were involved in the staging/murder.

Comment author: Jack 14 December 2009 07:26:21AM 1 point [-]

The universe of people who would have incentive to stage a burglary consists of just about everyone but actual burglars. If the police think that the murder is part of a botched burglary that throws them off the scent of stalkers, sex criminals and people romantically connected to Kercher (along with anyone who lived there or could plausibly have been invited in). Guede, in particular doesn't appear to be the brightest guy around. It seems more that plausible to me that he thought staging a break-in would help his case. He left physical evidence everywhere so on the fly he came up with the story of an anonymous attacker entering while he was in the bathroom. Then he breaks the window to try and create evidence consistent with his story. He doesn't flush the toilet for the same reason.

Or maybe the intruder went through Kercher's belonging looking for incriminating evidence-- love letters say-- and then made a mess of the roommates room to cover the search up.

Obviously I don't have any particular reason to privilege those scenarios but they seem to me about as plausible as two students without criminal experience or evident motive committing a rape-murder and not leaving any physical evidence behind. Remember, a rationale for staging a break-in doesn't have to be flawless. It just has to have enough surface sensibility that it would seem worth doing to Kercher's murderer/s.

Comment author: AnnaGilmour 15 December 2009 04:32:42PM 1 point [-]

The idea of a staged burglary came from Mignini and was unsubstantiated. Since then, it has been debunked. He claimed it was staged due to two shards of glass on clothing. Those shards close up were revealed to be polka dots.

Comment author: kodos96 14 December 2009 06:20:50PM 0 points [-]

This assumption that at least part of the burglary/break in was staged seems to me entirely unjustified. The only thing I've heard offered to support it is that the broken glass was on top of the strewn clothes, but seriously that doesn't prove anything... maybe the clothes were just strewn across the room innocently... maybe the glass just happened by chance to end up on top at the end of the clothes being mucked about with.... theres an infinite possible number of explanations that don't involve anything being staged.

And as to the assertion that it was staged since it looked like a burglary but nothing was stolen, thats simply not true: kercher's two cellphones were stolen, at a minimum (any number of other things might also have been stolen, but just not noticed missing, due to their owner not being around to point them out)

Comment author: Jack 14 December 2009 07:26:45PM 1 point [-]

Sorry, the clothes were strewn across the room innocently? By whom? For what possible reason? If the girl who lived in the room hadn't said anything about the matter I'd assume she was just messy. But that wasn't her testimony. The matter of the glass on top of the clothes depends on how much glass was found on top of the clothes. But I agree that it could have happened even if the window was broken first.

The two cell phones weren't being stolen isn't evidence that someone broke to steal them since they ended up tossed in someone's garden and not sold to someone. Something else might have been stolen but 1) the roommates and the family of the victim are probably capable of making a good accounting of Kercher's valuable possessions. Presumably this was done by the police, though their competence is definitely suspect at this point. And 2) it is improbable that someone breaking in to steal things would only happen to steal those things which belonged to the person they also killed and only those things her family and friends wouldn't notice missing.

The story that actually explains that a burglary without missing property is that the thief entered, was surprised by Kertcher, killed her (and raped her?) and then panicked and decided not to steal anything for fear it would implicate them.

Comment author: Morendil 13 December 2009 10:47:25AM *  12 points [-]

Good points, marred by what appears at first blush like double standards. Why are you willing to selectively discount some DNA evidence while you admit other ?

You say "the supposed Sollecito DNA on Meredith's bra clasp just plain does not count" - what is that "supposed" doing in here ? The FOA site admits that the clasp was shown to carry small amounts of Sollecito's DNA.

Why does it "not count" ? Admittedly, the handling of that evidence may not have been up to the standards normally demanded by the judicial system, but why should that matter to a Bayesian analysis ? All we're interested in as Bayesians is the ratio between P(DNA on clasp|Sollecito guilty) and P(DNA on clasp|Sollecito not guilty).

The defense may well have its own convenient narratives about how Sollecito's DNA "could have been transferred to the fastener in any number of ways" owing to carelessness on the part of the police. Those narratives are just as much noise as all the other noise you've pointed to. The details of US Department of Justice guidelines for forensics are also burdensome details for the defense.

The danger of coming across as arrogant - that is, more confident than your own entanglement with the evidence justifies, not the jurors' or someone else's - is that it provides others with an excuse to abandon the hard work of thinking rationally about the case, and letting themselves be swayed by the affective components: pretty pictures of Meredith or Amanda.

What I liked about your previous post was that, without any rah-rah propaganda about rationality, you outlined a procedure for laying out our current state of (un)certainty while minimizing some of the predictable biases. There was something delightful about the implausibly level-headed discussion thread it generated. We started with an open, almost playful invitation to rationality, in a spirit of inquiry.

Here we seem to be back to a spirit of established truth and advocacy, a spirit of "getting at the teacher's answer" - we even get averaging of the students' grades. I'm expecting the discussion to be more run-of-the mill, too. (Your Postscript is also mildly insulting; if someone is smart enough to arrive at the appropriate level of uncertainty in Knox's guilt, then surely they are smart enough to figure out what to do about it.)

Here, I believe, is the bottom line. Make rationality fun, and people will play along without for a second realizing it's hard work. Make rationality sound like something people ought to have, to be as smart and righteous as you - that's a turn-off.

Comment author: mattnewport 13 December 2009 07:30:13PM 2 points [-]

The Friends of Amanda site claims:

Tests also revealed the DNA of at least three other unidentified people on the bra fastener.

If that is true then it suggests to me that finding Sollecito's DNA as well is not very strong evidence for anything.

Comment author: Morendil 13 December 2009 09:12:53PM 3 points [-]

Can you explain your reasoning here, in terms of P(other folks' DNA on clasp|Sollecito guilty) vs P(other folks' DNA on clasp|Sollecito not guilty) ?

I can understand how this fact might be "suggestive" of something, but "suggestive" is the same kind of thinking as "suspicious": it's narrative rather than analytical.

Comment author: mattnewport 13 December 2009 11:47:45PM *  10 points [-]

It seems to me that the prosecution's case against Sollecito relies quite heavily on the evidence they claim proves he was present at the crime scene since they have no other solid evidence against him.

The reasoning used by the prosecution is basically what Jaynes calls the 'policeman's syllogism' in Probability Theory: The Logic of Science. The reasoning is of the form:

  • If A is true, then B becomes more plausible
  • B is true
  • Therefore, A becomes more plausible

Here A is (Sollecito was present at the crime scene) and B is (DNA tests on the bra clasp detected Sollecito's DNA). If we use C to stand for our background knowledge then by Bayes theorem:

p(A|BC) = p(A|C) * (p(B|AC) / p(B|C))

The premise of the policeman's syllogism "If A is true, then B becomes more plausible" takes the form

p(B|AC) > p(B|C)

And by Bayes theorem if this premise is true then:

p(A|BC) > p(A|C)

as stated in the syllogism. Now the significance of the evidence B depends on the magnitude of p(B|C) - the only way finding B to be true can greatly increase the plausibility of A is if p(B|C) is very small relative to p(B|AC). In other words, the prosecution's argument rests on the background probability of finding Sollectio's DNA on the bra clasp being very low relative to the probability of finding it if he were present at the crime scene.

Now it seems to me that the fact that the DNA of several other unidentified individuals (who it is not suggested were present at the crime scene) was also found on the bra clasp indicates that p(B|C) is not so much smaller than p(B|AC). B is only strong evidence for A if DNA on the clasp is much more likely if the person was present at the crime scene but we have several counter examples of DNA on the clasp from individuals who were not at the crime scene so we have reason to doubt that p(B|AC) is much greater than p(B|C) and therefore reason to doubt the significance of the evidence.

Comment author: Cyan 14 December 2009 03:26:08AM 1 point [-]

Very well said.

Comment author: Morendil 14 December 2009 07:24:38AM 1 point [-]

Now that is analytical.

And by and large I agree with the analysis - that is, I agree that how much weight to give to that particular evidence is determined by your estimates of P(B|AC) and p(B|C).

We may yet disagree on these, but if we do it should be on the basis of models that further evidence can in principle confirm or rule out, for instance whose DNA exactly was found on the clasp - does it match the investigators' ? They were at the crime scene. Contamination of that sort would help (in a Bayesian sense) the prosecution, not the defense.

What I take issue with is to say that something "does not count" when we have a previous commitment to take into account every bit of evidence available to us. Either we use Bayesian standards of inquiry, or judicial standards of inquiry, but we do not cherry-pick which is convenient to a given point we want to make.

Comment author: AnnaGilmour 15 December 2009 01:45:36AM 2 points [-]

Check out the blog ScienceSpheres by Mark Waterbury. He discusses at length the issues of negative controls, field controls, and pinpoints the problems with the LCN DNA analysis. One of his key points is that the mistakes in the evidence gathering and testing aren't hit or miss - they are consistent - which reveals a pattern of intention.

Comment author: brazil84 13 December 2009 10:57:19AM 2 points [-]

And by the way, if one takes your approach of starting from the crime scene and working backwards you must immediately confront the apparent staging of a break-in at the victim's residence. Which, if I recall correctly, was what initially made the Italian authorities suspicious of Amanda Knox.

Comment author: kodos96 14 December 2009 06:01:26PM 4 points [-]

What exactly do you think makes it "apparently staged"? All the evidence I'm aware of is that it looked like a burglary cause it was a burglary.

Comment author: brazil84 14 December 2009 11:03:32PM 0 points [-]

To avoid any confusion, can you tell me what you mean by "burglary"? Sorry to be pedantic, but the term apparently means different things to different people. To me, it means breaking into a structure for the purposes of committing a serious crime.

Comment author: Blueberry 14 December 2009 11:10:08PM 0 points [-]

You forgot "in a dwelling during the nighttime." ;)

Comment author: brazil84 14 December 2009 11:32:34PM 0 points [-]

Lol . . . . yes, that's the traditional formulation.

Comment author: Jack 13 December 2009 01:05:17PM *  6 points [-]

Can anyone find statistics that could tell us what is the probability the crime scene at any given murder contains physical evidence sufficient to indicate a suspect? I would expect it to be around .8-.9 but I don't really have any idea. I'm not convinced that that probability is high enough to completely outweigh the probability that AK and RS had something to do with the crime given that

  • they knew the victim

  • are sociable 21 and 24-year-olds (one of them studying abroad) without alibis on a Saturday night

  • the probability that Guede did not act alone (which is high or low depending on how well his presence explains all the evidence at the crime scene with a prior involving the chances any given murder involves more than one perpetrator) Obviously the absence of other physical evidence is evidence that he acted alone, so this value is the probability dictated by the other evidence, rearranged crime scene, broken windows etc.

  • the facts about the morning of November 2, the non-negligible probability RS called the police after the police had arrived, the short phone calls, even the weird behavior that can be explained, which once conjoined, looks like it is at least slightly indicative of being involved in Kercher's murder.

I don't think this is actually sufficient evidence to bring the probability AK and RS are guilty over .5. But it also isn't obvious to me that this evidence is "swamped" by the lack of physical evidence implicating them.

Comment author: Shalmanese 13 December 2009 02:32:57PM 12 points [-]

Wasn't there a post here a while back that talked about how anyone positing a confidence of 0.999 on something non-trivial was most likely to be suffering from their own cognitive biases?

Comment author: Yvain 13 December 2009 02:36:02PM 9 points [-]

No 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 at most.

Out of one thousand criminal trials in which the Less Wrong conventional wisdom gave the defendant a 35% chance of being guilty, you would expect to be able to correctly determine guilt nine hundred ninety nine times?

Comment author: Torben 13 December 2009 03:48:18PM 2 points [-]

Out of one thousand criminal trials in which the Less Wrong conventional wisdom gave the defendant a 35% chance of being guilty, you would expect to be able to correctly determine guilt nine hundred ninety nine times?

Maybe I'm missing something, but I think you read that wrong.

komponisto said the evidence should not cause anyone to change the prior probability much. Surely, for people in AK's reference class, the per-year probability of committing a 3-party sex killing is less than 0.001?

I think komponisto quite correctly described the effect of privileging the hypothesis, which might be what caused the LW community to be so much off from his estimate. Everybody seemed to be going backward from assuming AK's guilt at 50-50, whereas komponisto went forward from the background probability.

Comment author: gelisam 13 December 2009 05:56:35PM 1 point [-]

Everybody seemed to be going backward from assuming AK's guilt at 50-50, whereas komponisto went forward from the background probability.

I think I can see why. komponisto pretended to be a juror following the "innocent unless proven otherwise" mantra and updating on the evidence presented in the court. We, on the other hand, did what komponisto challenged us to do: figure out the answer to his riddle using the two websites he gave us. This being a riddle, not a court, we had no reason to favour one hypothesis over the other, hence the 50-50.

That being said, I did favour one hypothesis over the other (my stated priors were 75/75/25) because at the moment I paused to write down an approximation of my current beliefs, I had already updated on the evidence presented by komponisto himself in his post, namely, that there was a trial against AK and RS.

Maybe the reason why many of us gave so much importance to the fact that those particular individuals were on trial for murder was because it was our very first piece of information; and I don't think it's right for rationalists to do that.

Comment author: luzhin 13 December 2009 09:26:49PM *  0 points [-]

komponisto should not be going forward from the background probabilities because he isn't an experienced investigator with access to the crime scene. he's just a guy reading about evidence on the internet. a more reasonable prior for him to start with is, ''how often are people convicted of murder when they did not in fact commit a murder?'' (there are actual #s for this, too)

when juries sit around thinking, ''is this person guilty or not?'' they assume the investigators working on the case are competent. they assume, quite rightly, that there must be a damn good reason why reasonable investigators couldnt quickly dismiss a hypothesis with such an insanely low prior probability. lesswrong.com readers should do likewise.

Comment author: dilaudid 13 December 2009 05:23:15PM 23 points [-]

Komponisto makes a strange assertion. The prior is not the reference that "someone would commit murder" - there is a body. A more appropriate prior is "someone who lives with someone who was murdered committed that murder" - I'm guessing that base probability is of the order of 0.1. Once we take into account that AK and MK aren't in a relationship, AK is female, and there is very strong evidence that someone else committed the murder then I'd agree that the probability drops, but these pieces of evidence don't cancel out leaving us with the original prior - the final probability may be higher or lower.

Also the "complexity penalty on the prosecution's theory of the crime is enormous" - that may mean the case was flawed, but it's not evidence she didn't kill MK unless you are willing to give some weight to the conviction (at <0.001, I assume you are not). Or to put it another way, even if the prosecution is completely wrong you cannot set the probability of guilt to 0. This is like assuming AK is guilty because her parents criticized the Italian legal system.

Overall I hope I am a bit more cautious about my abilities than you. In the first half you explain why you, as a human being, cannot be trusted to be rational. Then you set out your case. Why should I trust your rationality, but not others'?

Comment author: brazil84 14 December 2009 03:48:16AM 3 points [-]

I think this is a good point, but I would go one step further. Because there was more than one crime committed. In addition to a murder, somebody tried to stage a burglary. Common sense says that whoever staged the burglary was also involved in the murder but it's still 2 separate crimes.

It seems to me that the prior probability that the person who staged the burglary is someone closely associated with Kercher, such as a roommate, is actually pretty high. A close associate would have a strong incentive to try to make the police think that a stranger committed the crime. Whereas a stranger or remote acquaintance would have little or no incentive to do so.

Comment author: ChristianKl 13 December 2009 05:36:17PM 1 point [-]

There something like a TV bias. In TV shows there often physical evidence at a crime scene that's needed for the narrative of the story. In real life there often isn't a lot of physical evidence.

That bias is strong enough to let some prospectors ask jurors about how much they watched shows like CSI to select jurors that don't believe that there has to be physical evidence.

To me it seems you are a victim of the bias that real life crime scenes look like TV crime scenes.

Comment author: wnoise 13 December 2009 05:51:12PM 5 points [-]

They did find lots of crime-scene evidence in this case -- pointing toward Guede.

Comment author: komponisto 14 December 2009 07:24:07AM *  1 point [-]

In general (with a very few idiosyncratic exceptions), I despise crime shows, and have never seen an episode of CSI in my life.

Comment author: Jack 14 December 2009 07:50:51AM 4 points [-]

Given the number of convicted people who were later exonerated by DNA evidence it isn't obvious to me that juries expecting physical evidence is a bad thing. One thing entailed by komponisto's discussion of the emphasis humans put social and mental facts is that the pre-CSI judicial system assigned too much weight to such facts and likely imprisoned innocent people. And it turns out they really did imprison innocent people. So maybe it is the judicial system's bias, not komponisto's...

Comment author: Unknowns 14 December 2009 07:53:15AM 0 points [-]

Even so, the number of people exonerated by later DNA evidence is nowhere near 90%.

Comment author: Jack 14 December 2009 07:59:40AM 0 points [-]

What is special about 90%?

Comment author: Unknowns 14 December 2009 08:01:48AM 0 points [-]

We're discussing a claim that someone convicted of murder has a 90-99% chance of being innocent. That could be true, but not merely because they used evidence other than DNA evidence.

Comment author: Jack 14 December 2009 08:23:55AM 2 points [-]

Oh. Obviously P(Guilty | untested DNA evidence) doesn't equal P(Guilty | no solid physical evidence of any kind & no motive & extensive physical evidence implicating someone else)... and I actually think .1 is too low a probability of Knox's guilt. I was just pointing out that the mere fact that CSI has lead to some jurors expecting physical evidence does not mean that those jurors are more biased than those content to convict without physical evidence. If we have an evolved bias to over-emphasize social and behavioral evidence then it is perfectly possible that watching CSI compensates for a bias rather than creates one.

Comment author: Sebastian_Hagen 13 December 2009 06:41:46PM *  6 points [-]

Excellent post. I don't think I'm ready to wield those sharp implements with quite so much flourish yet; the chance of lopping off my own limbs is currently too high.

However, there are some specific parts of your post I disagree with.

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.)

Agree completely. Now apply it both ways. Specifically:

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.

This is extremely weak evidence. If you think that psychology doesn't really matter (and I agree with that), then it notmatters in both directions. There's no obvious motive, but that's very weak evidence that no motive existed. We just don't have enough evidence for what these people really think like, relative to the population at large. Re. motive, I'd definitely stick with the prior for murderous intentions among associates.

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 [count]

I was surprised at you dismissing the knife DNA evidence. The linked FOA page claims:

Low Copy Number (LCN) tests, like the one performed on the knife blade, are regarded by many experts as inherently unreliable, because it is not possible to prevent biological contamination at the level of picograms. Even in well-run labs, control samples regularly show up with DNA that theoretically should not be there.

The actual experts doing DNA-testing in the case evidently thought that it was significant evidence. Wikipedia has an article on LCN, though a lot of the citations are broken. According to the article, the method went through an extensive review, and was finally cleared for use in the UK justice system (and with a fairly definite statement at that: "The CPS has not seen anything to suggest that any current problems exist with LCN"). The situation in some other western countries appears to be rather different, though. I still think this is fairly strong evidence, though much less so than I did before doing some research on the general acceptance of this test method.

While not particularly flattering to the defendants (how would you like to be told that there's a 35% chance you're a murderer?)

Keep in mind this verdict uses (among other pieces of information) the existing jury verdict as empirical evidence (and of course in our epistemological position, that's the right thing to do); if our judgements had been based on just the primary evidence - i.e. without an existing guilty verdict by a jury - these probabilities would have been lower.

Comment author: snarles 13 December 2009 07:04:39PM 10 points [-]

I'd like to suggest another type of rationality test for this site. The top contributors should randomly make posts that are flat-out wrong to see how they are received; and they should also randomly make legitimate posts under different names.

Comment author: wedrifid 13 December 2009 11:12:56PM 4 points [-]

I'd like to suggest another type of rationality test for this site. The top contributors should randomly make posts that are flat-out wrong to see how they are received; and they should also randomly make legitimate posts under different names.

When moving from my real name to this more anonymous persona the responses to my comments were noticeably different. This effect diminished over time. I've actually considered creating mechanisms by which I could make a self-blinded test of the effect of names on reception, but this was more with OkCupid in mind. Perhaps because investigating human psychology is even more fun than the dating itself.

Comment author: Douglas_Knight 14 December 2009 02:08:53AM 4 points [-]

When moving from my real name to this more anonymous persona the responses to my comments were noticeably different.

Could you elaborate?

Comment author: wedrifid 14 December 2009 05:15:59AM 7 points [-]

Could you elaborate?

Sure. I'll compare what I perceive to be the differences between wedrifid now and, say, < 100 karma wedrifid. The difference in reception was more apparent given that wedrifid didn't have the steep learning curve associated with learning a new micro-culture. * Comprehension. Comments by young wedrifid were less likely comprehended than comments of approximately equal quality now. Not understanding people is a signal of high status. It obliges the lower status people to spend effort to second guess your way of thinking and adapt towards your preferred set of concepts in order to communicate with you. This signalling appears to run deeper than an outward display. Higher status people at times seem actually unable to comprehend things that would otherwise be in their grasp, often to their own detriment. * Rebuttal. People were more likely to reply with retorts to upstart-wedrifid and, more significantly, provided less or lower quality reasons when doing so. This is to be expected less from high status people and more from people with more moderate status who would like to raise it. (There isn't much point going one up if you have to reach 3 down in order to do so.) I get less replies now that I consider to be absolutely idiotic. Again, I don't think that is just because people generate inane nonsense then decide whether or not to post it by whether they recipient is a newbie or for some reason other reason an easy target (eg. out-of-group or currently being scapegoated). I think the calibration of carefulness is built in to the rebuttal generation system.

Of course, I don't know how much of my perception is just me seeing what I expect to see: normal social behaviour. I also don't think this effect would be sufficient to overshadow a top level post by a renamed Yvain or Eliezer. I would probably just wonder who this amazing new poster was. I still remember Yvain catching me by surprise with that burst of brilliant posting in LessWrong's early weeks. Those seem to be received no worse than Eliezer's would have been if he were still posting regularly. Although come to think of it I may have rejected WeiDai's probability posts if I hadn't seen the quality of his other contributions. They are confusing enough topics that I needed to take a while to absorb them before they made sense. Of course, maybe I would have been convinced anyway while trying to write a rebuttal to RenamedWei_Dai and realising that he was absolutely right.

I am intrigued somewhat by snarles' other suggestion, the posts by top contributors that are flat out wrong. My dark side wants to suggest that maybe that is the explanation that those anthropic reasoning posts are examples of this! (Of course, a somewhat wiser side of myself reminds me that it is conceivable that I am confused, not Eliezer.)

Comment author: ciphergoth 14 December 2009 08:55:52PM 1 point [-]

Eliezer has made it explicit on several occasions that he never does this. I'm not saying it's necessarily a bad idea, but he doesn't do it.

Comment author: Eliezer_Yudkowsky 14 December 2009 08:58:07PM 2 points [-]

Aye, and I'll say it again just to be sure. If I want to say something that's not true, I write a story and put it in the mouth of a fictional character.

Comment author: AnnaGilmour 15 December 2009 01:41:47AM 0 points [-]

Another way to go about it is to be contributor-blind. That's what I do.

Comment author: mattnewport 15 December 2009 02:12:23AM 1 point [-]

That's a noble goal but I'm sure you're aware that merely having the intent to avoid a bias does not necessarily confer immunity to that bias. Psychological research is full of examples of people still suffering from a bias even when they have been made aware of it and protest strongly that they are not under its influence.

Comment author: AnnaGilmour 15 December 2009 02:23:05AM 1 point [-]

I meant, as a general rule of thumb. I code/scan/whatnot for the logic, and then also avert my gaze away from the name. I check the name after I have my response for verification. I like to read things like the Wikipedia list of fallacies so it is an interest of mine. With so much awareness these days of perceptual error (and similar) I find that people over-correct the other way to adjust for it. But I understand that I may be influenced by the name and not know it though I really do block it out of my visual field - as odd as that may seem. I check for those kinds of things as a basic rule and tendency. But I love to be wrong and to be challenged, and I know I have areas to sharpen. Logic is very pleasing to me to the point where when someone points out a problem with mine, I feel pleasure. Okay, enough of my testimonial... I am just happy to find this great site! I love how specific everyone gets. A joy... :)

Comment author: bogdanb 13 December 2009 09:37:34PM *  13 points [-]

I'm a bit curious about something:

If read your post correctly,* you feel that you can discount as pretty much irrelevant the opinions of quite a lot of people (jurors, police, etc), on the simple basis that people can be spectacularly wrong on occasion. (* I'm really not sure about this.)

In fact, as far as I can tell, you start from “clean” priors and do all your updating based only on the “physical evidence”; no opinions entering your calculation.

This seems almost OK, but something's nagging at me: how can you obtain thirty bits of confidence in your estimate using only evidence received from other people, via the Internet?

I'm also not sure about this, but your post seems to imply that a “good Bayesian” would be expected to assign that amount of confidence to his answer after only a couple of hours of surfing the Internet. I'm not saying that's impossible, but it really sounds very unlikely to me.

I'd very much like to see a chain of numerical reasoning that reasonably puts a 1:1000 upper-bound on the likelihood that Guédé is innocent, without starting with implicit assumptions of 100% certainty about data read from the net.* If you think an hour on the Internet is enough to reach that kind of certainty, I don't see why writing the calculations (for an upper bound, not the precise value) would take much longer, assuming that one would be gathering data and doing the calculations in one's head during that hour.

(*: EDIT for clarification. By this I mean that, for instance, given claimed evidence E in support of theory T, you don't update on the probability of T given E, but update on the probability of T given “I've read on the Internet that E”. Of course, many claims of E on the Internet have some weight, but I doubt two hours of Internet reading can add lots of weight on non-trivial subjects.)

Comment author: LauraABJ 13 December 2009 09:41:26PM 2 points [-]

Ok- many people have already pointed out that the prior should be probability of having committed murder if you live in the same house as someone murdered. Now, I would like to add that the psychological evidence shouldn't be completely and utterly discounted.

1) Knox knew Guede and Kercher, the murderer and the murdered, and is thus not random. This alone is reason for suspicion (though certainly not indictment).

2) Knox wrote a story about the drugging and rape of a young woman. Anyone have statistics on how many murderers have written such rape- fantasies or how many fantasy writers are violent offenders?

3) Knox really wasn't able to give a consistent story about her whereabouts. (I discount this a lot more now knowing her testimony was given under duress, but can't dismiss it entirely.)

Now, this doesn't add up to all that much, but certainly more than the p = 0.001 you are claiming. I think the odds are higher that she talked with Guede i n passing before he raped and murdered kercher than that she was there when it happened (due to absence of evidence and failure of guede to implicate her).

Comment author: Blueberry 13 December 2009 09:45:08PM 2 points [-]

Knox wrote a story about the drugging and rape of a young woman.

Did she really? Link/cite please? Is the story available anywhere?

I realize it may affect probability calculations, but it just doesn't seem fair to use someone's fiction against him.

Comment author: LauraABJ 13 December 2009 09:56:29PM 2 points [-]

I can't find it- though the excerpts given in the NYTimes do sound more like a soap-opera than a rape-fantasy.

Comment author: Kevin 14 December 2009 04:29:51AM 3 points [-]

No link handy, but it was for a class assignment and Knox's story was by far not the most violent out of the stories written by her peers.

Comment author: wedrifid 14 December 2009 05:42:51AM 3 points [-]

No link handy, but it was for a class assignment and Knox's story was by far not the most violent out of the stories written by her peers.

"I can't do the assignment miss, because I don't want to be imprisoned for murder!" I'm going to have children just so I can recommend that excuse to them.

Comment author: Bo102010 14 December 2009 01:55:06AM 1 point [-]

This was a brilliant post. You deserve buckets of karma.

I didn't read the first part of the series until later - I wish I could have participated.

Comment author: komponisto 14 December 2009 07:59:57AM 2 points [-]

Upvoted for making me feel good, after I was bummed out for having overstated my case. :-)

Comment author: AnnaGilmour 15 December 2009 12:31:40AM *  4 points [-]

I don't think you overstated your case. The point was that there is an almost absolute disparity of evidence between Guede's guilt and Amanda or Raffaele's guilt.

Comment author: cheesedaemon 14 December 2009 03:43:41AM 0 points [-]

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...

Shouldn't this start with "if you frequently..." ?

Comment author: komponisto 14 December 2009 06:00:07AM 4 points [-]

Post now revised in light of comments.

Comment author: Jack 14 December 2009 06:16:03AM 0 points [-]

1.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 0.01 or 0.1 at most.

What information do these new priors reflect? Obviously 1-10% of upper-middle class female college students with no history of criminal activity won't commit murder over the next 12 months so I assume that these priors are taking something else into account- like the fact that she lived with a murder victim. But can you say what else you've included? (Or point me if you already have somewhere).

Comment author: komponisto 14 December 2009 07:01:22AM *  0 points [-]

What's going on here is that I'm still trying to figure out how I want to revise that sentence. I may just go ahead and cross it out, since I think the whole issue of "what the prior should be" is a distraction.

EDIT: Done.

Comment author: [deleted] 14 December 2009 07:34:16AM 4 points [-]

I posted this in response to the Hacker News thread but i wanted to cross-post it here. I appologise for not having read all the comments here first before responding. It seems your post is largely misrepresenting the facts of the case.

Have you read the judge's summary?

http://www.zimbio.com/Amanda+Knox/articles/58/Understanding+Micheli+2+Judge+Micheli+Rejected

A few key points in the prosecutions case:

  • 4 mixed DNA samples of the Knox and Kercher. Bloody footprints that match. Blood on the tap put Knox at the crime scene that evening or in the early morning.
  • A bloody bra in the washing machine
  • Attempts to frame an innocent man for the crime.
  • Repeated lying to authorities regarding her whereabouts. Still no fixed alibi.
  • Knox and Kercher's house was cleaned with bleach.
  • Sollecito's trainers were cleaned with bleach. A defect in the sole match a blood print on the scene. The decision went through going through 19 expert judges and 6 lay judges. Conviction was unanimous.
  • Eye witness putting all 3 suspects together outside the cottage that night, and the night previous.
  • Knox and Sollecito standing outside the crime scene when the police arrived with mop and bucket.

Certainly, we can ignore some of the strange behaviour of the convicted (the phone calls, the lies, her past). But the case is much stronger than what this article makes out. It's also worth pointing out that various aspects reported in the media aren't correct - such as the 14-hour interrogation and police violence.

Rational thought takes anyone first to the conclusion that there was more than one killer. Guede left the scene soon after the murder (eye witness reports; evidence of cleaning, Guede's own statement). It is clear the crime scene was later returned to, and altered to cover evidence (faked break-in; footprints; removal of bra from the body). With all the additional evidence against Knox and Sollecito, physical and circumstantial, clear motive, and consitantly irrational behaviour, gives a very strong prosecution case.

Whether they are guilty or not isn't for me to say, nor would i think i'm qualified enough to give such probabilities. But the case appears to be largely misrepresented in your blog post.

Comment author: rmattbill 14 December 2009 06:21:07PM 11 points [-]

Hi Nick, While I appreciate that you don't seem to be one of the irrational Knox haters, your comments about the evidence contain a couple of errors, and the one that don't leave out some important facts which cast doubt on almost every single claim.

-Yes, Knox's DNA was founded mingled with Kercher's, but almost all of it was in the bathroom they shared. It would've been almost impossible NOT to find a few instances of their DNA mixed in such a small place, and a place where humans shed copious amounts of hair and skin cells, and even blood (shaving cuts, etc.).

-Not one shred of Knox's DNA was found in Kercher's room. The idea that she somehow managed to remove every microscopic shred of her DNA, while leaving Rudy Guede's behind, is completely implausible. This alone casts enormous doubt on the prosecution's theory. DNA in the bathroom simply proves Knox and Kercher lived together. A total lack of DNA in Kercher's room is compelling evidence she was not at the scene of the crime.

-No traces of bleach were found at the crime scene. Numerous rumors about bleach are clogging message boards all over the internet, including false stories about receipts which showed Knox buying bleach twice the morning after the murder, but those stories did not pan out and were not presented at trial. One witness emerged, seven months AFTER the murder, to say he saw Knox buy bleach in his store, but his co-worker said he was lying. This testimony must be treated skeptically, since no traces of bleach were found at the crime scene. The crime scene was extensively examined using Luminol, and in addition to revealing blood, Luminol illuminates trace amounts of bleach.

-The Albanian witness who says he says Knox and Sollecito with Guede is the only person to allege that the three knew each other, and his testimony at the trial was contradictory and underwhelming, to say the least. Throughout his interrogation and trial, Guede denied knowing Knox or Sollecito, and denied they were at the house. He knew what Amanda looked like, as he had twice visited the downstairs neighbors to play basketball, but didn't even know what Sollecito looked like.

-Knox and Sollecito had taken the mop to Sollecito's house to mop up water that had come from a broken pipe under the sink. Was any blood or DNA found on the mop?

-Whether or not the bloody footprint on the bath mat matches Sollecito or Guede is highly debatable. Another bloody footprint, found in Kercher's room, was a definitive match for Guede. Although people have posted claims about bloody footprints revealed using Luminol, those prints were left by sweat and oil, and tested negative for any trace of blood.

Briefly, on a few other points, the prosecution's fingerprint expert said it was not unusual that he didn't find usable prints for Knox in her own bedroom. There were lots of smeared prints (fingerprints, made by a tiny amount of oil on our skin, are easily disturbed), just no USABLE prints. Lots of smeared and partial prints is evidence the room was NOT wiped down, and he testified he saw no evidence of a wipe down.

Last, the so-called "fake" break-in is highly contentious issue and neither conclusion can be viewed as beyond doubt. The prosecution tried to say it's impossible to climb the wall (ignoring photos of a 40-year old Italian detective in dress slacks and dress shoes easily scaling the bars on the window below), but Judge Micheli dismissed them, noting that anyone in reasonable shape could've easily climbed into the window. Rudy Guede, who had committed at least three burglaries in the previous week, was 20 years old, and a former semi-pro athlete.

But again, I appreciate your rational approach to the evidence, and respect your opinion. It's nice to see someone on the internet talking about the evidence, and not just Knox's immature behavior.

Cheers, Matt

Comment author: Jack 14 December 2009 08:05:23PM *  4 points [-]

Rudy Guede, who had committed at least three burglaries in the previous week

Jeeze, how did I miss that. Do you have a link?

Edit: Also. New people! Welcome.

Comment author: rmattbill 14 December 2009 11:37:57PM 5 points [-]

Sorry, my post contained an error. It was three burglaries in five weeks, not one week.

This is from an article at the Daily Mail entitled "Amanda Knox: The Troubling Doubts Over Foxy Knoxy's Role in Meredith Kercher's Murder."

Here's the link: http://www.dailymail.co.uk/news/article-1234298/Amanda-Knox-The-troubling-doubts-Foxy-Knoxys-role-Meredith-Kerchers-murder.html

And the pertinent text from the article:

On September 27, 2007 - five weeks before the killing - Perugia bar tender Cristian Tramantano heard a noise downstairs in his home and found Guede wandering around with a large knife. Tramantano recognised Guede from his work in a nightclub.

There was a confrontation between the two, which ended when Guede ran away. On four occasions, Tramantano went to Perugia's central police station to report the break-in, identify Guede as the culprit and to detail how the intruder was armed and threatened him.

On each occasion, he says he was ignored and the police refused to log his complaint.

The following weekend, there was a break-in at an English-speaking nursery school in Milan in which 2,000 euros and a digital camera were stolen. The school owner, Maria Antoinette Salvadori del Prato, reported it to her local police station.

Three weeks later, on Saturday, October 27 - one week before the murder - Mrs Prato arrived at the school early in the morning with a locksmith to replace the front door, only to be confronted by Guede standing in the main entrance.

Police were called and Guede questioned. A stolen laptop, digital camera and ten-inch kitchen knife were found in his backpack.

But instead of being arrested and charged, Guede was merely escorted to Milan central railway station and placed on a train back to Perugia.

In the interim, on the weekend of October 13, there had been a break-in at the office of lawyers Paolo Brocchi and Luigi Palazzoli, in which a firstfloor window was smashed - similar to the break-in at Meredith's house. A computer and other items were stolen.

They were later found in Guede's possession, but he was not arrested or charged.

Comment author: zero_call 14 December 2009 11:46:00PM 2 points [-]

The Daily Mail is a British tabloid... frequently posting completely fraudulent information about football players, for example... check your sources friend...

Comment author: AnnaGilmour 15 December 2009 12:59:20AM 0 points [-]

The above quoted story was reported in more than just the Daily Mail. I will look for a few of the other articles.

Comment author: AnnaGilmour 15 December 2009 12:57:58AM 0 points [-]

I read three in the week leading up to the murder, as well. I should recheck that. But it is confirmed that he traveled with a 16 inch knife "for protection" and that he had various run-ins resulting in complaints to police that were ignored by the police.

Comment author: AnnaGilmour 15 December 2009 12:29:12AM 0 points [-]

Yes... a huge fact that did not hit the headlines in any big way.

Comment author: Jack 15 December 2009 02:33:18AM 0 points [-]

I'm still waiting on non-tabloid verification. A quick look at the paper's wikipedia page yields a long list of successful libel suits.

Comment author: AnnaGilmour 15 December 2009 04:19:32PM *  0 points [-]

Sorry... I'm in the Pacific Time Zone... Just got back to the computer... I am looking into non Daily Mail/Mirror articles. Am at work, so have to look as I can. I do know it was part of the court record and that the kindergarten teacher testified and a police person might have as well. I am looking for something on the court record. Candace Dempsey of the Seattle Post Intelligencer was following that aspect of the case and wrote about it in her blog Italian Woman at the Table. Guede's criminal history is established as fact, as well as the police turning away reports about him.

Comment author: [deleted] 14 December 2009 09:42:15PM *  0 points [-]

Thanks for taking your time with your thoughtful and detailed response. I will go through each point in turn below. It's worth mentioning now that I don't actually mean to argue for or against the conviction specifically; rather I feel the prosecution case is significantly stronger than US media has generally reported. Also I'm neither a lawyer, phorensic scientist or logician, so I apologize in advance for any technical mistakes. I'm just trying to assess the information myself that's available on the internet and come to an informed opinion.

Certainly some of the evidence appears flawed: the bra clasp, the alleged murder weapon, the eye witness. But we do know that the Judge, and a panel of 19 legal experts, admitted these as evidence. I can't really comment on whether the blood trace on the knife, for example, is sufficient enough to admit the evidence; similarly whether the bra clasp can become contaminated. But the evidence was admitted, and strongly contested, consider and eventually accepted by the panel and the jury.

  • The DNA evidence: Firstly, I think the important point is that 4 blood samples from the bathroom were found with mixed Knox-Kercher DNA. From truejustice.org: " Yes, it does seem that the investigative methods were sloppy and not all samples may be reliable (I acknowledge that there are some problems with the prosecution’s case). But I have yet to read even one article where a reputable DNA expert can explain why sloppy police procedures would result in four separate mixed blood samples".

  • Also this site (http://www.thedailybeast.com/blogs-and-stories/2009-05-24/will-dna-damn-amanda-knox-/), reporting on the Forensic biologist Patrizia Stefanoni testifying for 9 hours on the stand, notes "But perhaps more damning even than the knife was Stefanoni’s testimony that a mix of Knox’s DNA and Kercher’s blood was found on the floor in the bedroom of a third roommate, Filomena Romanelli [...] her window was broken with a large rock that prosecutors believe was used to stage a break-in. The mixed Knox-Kercher trace was found after investigators used luminol, a substance used in forensic science to bring out blood that had been cleaned up."

  • The bleach: The truejustice.org site has various mentions of use of bleach on the alleged murder weapon, shoes, and apartment (not crime scene), such as "A police officer who led a search of Sollecito’s apartment added weight to the prosecution’s assertion that the double DNA knife had been cleaned with bleach. He testified that he had been struck by 'the powerful smell of bleach'.". I agree this is far from damning evidence of a cleanup, and the lack of the recipe being produced at trial weakens this evidence substancially.

  • The Albanian witness: From the translation of the Micheli report, "Judge Micheli examines the evidence of Hekuran Kokomani and finds him far from discredited .. Hekuran Kokomani was in the vicinity of the cottage on both 31st Oct. and 1st Nov isn’t in doubt ... details which he gave of the breakdown of the car, the tow truck and the people involved weren’t known by anyone else.".

  • The police who found Knox and Sollecito at the crime scene were a different police force there on other business (the mobile phone/bomb hoax), so I assume at the time they didn't think much of it and so the mop wasn't detained as part of the crime scene. Sollecito said it was being used to mop up water that had come from a broken pipe under the sink; knox said it was to mop up water from the pasta spilt cooking the night before. Sollecito later sent an email saying they ate something other than pasta that night.

  • Your point that there were no bloody footprints that fit Knox/Sollecito doesn't match with what I'm reading from the report, including "bloody bare footprints which show up with luminol and fit Knox’s and Sollecito’s feet" by the front door, suggesting entry through that route, and "Bloody footprints made visible with luminol in Filomena’s room contain Meredith’s DNA". The source of this is all truejustice.org, but supposedly this is based on impartial translations of the freely available italian report. I have no other source to go on and don't speak Italian, do you think these are falsehoods? Are there alternative translations/summaries available?

  • Regarding the 'fake break-in', how did the defence respond to the claim that glass lay on top of clothes that had been disturbed during or after the attack?

  • Only final point, "Rudy Guede, who had committed at least three burglaries in the previous week", is there a source for this information?

Comment author: rmattbill 15 December 2009 02:22:37AM 3 points [-]

Hi Nick,

Thanks for the response.

Regarding the bleach, no evidence was ever presented that anything had been bleached. This story took on a life of it's own after the phony receipts story began circulating. I believe the Judge blocked at least one officer from testifying that he smelled bleach, and was only allowed to say that Sollecito's apartment smelled "clean," because the bleach smell was not listed in the initial report, and was added later, after the false reports about the receipts.

Despite the deference True Justice shows for every bit of evidence that favors Knox's guilt, Kokamani's testimony was ludicrous. He claimed that when he saw Knox, Sollecito and Guede together, that Sollecito (a meek computer nerd by all acounts), punched him in the face, and that Knox whipped out a 16 inch (!!!) knife, and said "Come here you! I'll show you!" and that he escaped by hurling olives and a cell phone at her. His testimony contradicted his original statement on many key points, and he had been arrested on drug charges before his testimony.

Regarding the footprints, my understanding is that two bloody shoe prints were found. One in Kercher's room that matched Rudy Guede, and another on the bath mat in the bathroom, that was a partial. From everything I've read, the partial print in the bathroom is a mess. It's certainly hard to tell anything from the photos. At various points, the prosecution said it was Knox's, then Guede's, then Sollecito's. The defenses expert witness made a strong case that it was Guede's, but I don't think anyone can conclusively prove anything one way or the other because it's only a partial print.

The other footprints were revealed by Luminol, but what True Justice leaves out is that every single one (except for the two I mentioned above), tested negative for the presence of blood. If the footprints weren't bloody, they don't really say anything about the crime, especially since Knox and Sollecito admit to being in the house that morning, before the body was discovered.

There are two good papers on the footprints at friendsofamandaknox dot org. Of course they're biased in Amanda's favor, but not any more so than True Justice is in the other direction.

I'm not surprised that some of Kercher's blood was mixed with Knox's DNA in the bathroom, since Knox's DNA could've come from anything. If a drop of blood splashed onto a dead skin cell of Knox's, the result would've been DNA from both women in the drop of blood. And that doesn't take into account the sloppy (by U.S. standards) forensics work done by the Italian police who could've easily, and innocently, intermingled DNA which is, often, invisible to the naked eye.

This is apparently what happened with the bra clasp which was left sitting on the floor for 47 days, was moved several times by unknown persons, and contains the DNA of at least three other people (and those people are not Kercher, Knox, Guede, or the other roommates or their boyfriends). The DNA either belongs to police who were not following procedure, or was picked up in the lab due to improper handling.

In the crime scene photos, it doesn't appear there is any glass on top of the clothes, nor did the police present photos of such a thing at trial. One of the biggest misconceptions is that the glass was on top of Kercher's clothes in her room. If this is true, the intruder could hardly have ripped Kercher's clothes off before breaking in through the window, but in fact the clothes were in Filomena's room. She testified she didn't leave any clothes out, hence the claim the break in was staged. But Filomena also could be wrong, she certainly wouldn't be the first witness to misremember something. Also, Filomena was allowed into her room no less than three times before the police finally sealed it, so it's hard to say exactly how the clothes and glass were intermingled before they were disturbed. It's possible the break-in was staged, but given Guede's past burglaries, and Occam's Razor, it seems likely that Guede broke into the house. If the break-in was staged, the prosecution did not manage to prove it beyond a reasonable doubt, at least not to my mind.

Last, I posted a separate comment with the link to the Daily Mail story about Guede's other break-ins.

Comment author: [deleted] 15 December 2009 04:26:36PM *  1 point [-]

You seem to be privy to a lot of information that I'm not, were you at the trial, or otherwise have better knowledge that the sourced information on the internet? Or is it from reading the 100-page Judge's report of the Guede case? I haven't heard before many of the things you've mentioned in your previous post. Also, some of the things seem to contradict what I've quoted above, a lot coming from the translation of Judge's summary. For example:

  • " I believe the Judge blocked at least one officer from testifying that he smelled bleach"

  • The specific details of Kokamani's testimony.

  • Information like " At various points, the prosecution said it was Knox's, then Guede's, then Sollecito's".

  • The papers on friendsofamandaknox don't give any sources. How do we know the information is good? I'm sure we could level the same criticism to truejustice.org, but many of the details they have linked to outside sources.

  • That the mixed DNA can easily be explained away, and DNA can be easily contaminated (there are various expert witnesses at the Guede trial who state otherwise)

  • That the bra clasp contained DNA of 3 other people.

  • "it doesn't appear there is any glass on top of the clothes", this contradicts what I've read from the Judge's report. You then go on to explain how glass could have got on top of the clothes (filomena allowed back in to the room), so I'm not sure which you are stating?

  • Regarding the Daily Mail story - as other posters have mentioned, the Daily Mail certainly isn't a reliable news source, unfortunately. And in general, even a well respected media source alone probably isn't good enough as a source, given how misreported the case has been (like the bleach receipt, the 14-hour interrogation, etc)

So again, I'm still not sure the truejustice.org summary of the Judge's document on the Guede case should be considered reliable, do you doubt some of the points? I'm using this to base a lot of my reasoning.

If it is an accurate summary, then it represents the decision of a large panel of law experts, that disagree with many of your arguments. So it seems either you are suggested (a) this translation Judge's summary is inaccurate, or (b) you disagree with the decision of the Judge and panel on many key points. If it's (a), I would certainly like to read a better translation. If (b), why do you think you are better qualified to make decisions on forensic evidence than a panel of legal experts?

I think in the end I will have to wait 90 days for the summary of the case to be made publicly available to make my own decision on the likelihood of guilt. There are still great disparages between the "pro" and "con" sites about what happened in the court room, and exactly what evidence was and was not presented in court. You seem to disagree with the Judge's decisions in the G case a lot (that the break-in was not faked; that the DNA evidence is unreliable; that the eyewitness testimony should not be admitted as evidence). What we do know is that the Judge, along with a large panel of legal experts, did in fact accept this evidence. Is it not reasonable (and rational) for me to accept the decisions of experts in the field?

Comment author: rmattbill 15 December 2009 07:35:41AM 5 points [-]

Two more tidbits re: Kokomani (from annebremner.com):

To give you an example of how absurd it got, Kokomani said that when Amanda was yelling at him, he noticed a wide gap between her front teeth. So the judge asked Amanda to smile, and she did. There is no gap between her front teeth.

Nor could Kokomani have had a beer with Amanda and her Italian uncle in July of last year, as he claimed in court, because Amanda was not in Italy at that time and she does not have an Italian uncle.

Comment author: Unknowns 14 December 2009 06:07:21AM 0 points [-]

It looks like I have to do some updating too... based on the original version I had concluded that komponisto wasn't capable of updating, but it seems I was mistaken.

Comment author: Kevin 14 December 2009 07:25:31AM 1 point [-]
Comment author: Kevin 14 December 2009 08:20:44AM *  1 point [-]

I think it's important to establish that it is likely that Knox and Sollecito could be lying about large portions of the night's events. Certainly they have told some lies. They were even legally allowed to lie as witnesses in Italian court. They may very well have been at the apartment before or even during the murder. It still does not make them guilty of murder.

Comment author: lordweiner27 14 December 2009 11:20:01AM 12 points [-]

Having review your evidence and some other evidence that I was pointed in the direction of I have to admit I may have been wrong. Knox and the other guy are probably innocent.

There were a few things that lead me to my original conclusion: -The DNA evidence -Amanda changing her story -My belief that it was ridiculous that the police would go to all this effort to frame them if they were innocent.

The DNA evidence has been refuted, I can't say I understand this but I'm willing to accept there is a lot of doubt there.

Amanda changing her story seems like evidence that she is a liar and seems a ridiculous thing to do if you are a murder suspect. (I still think it was really stupid of her and totally the wrong thing to do.) But at the the time she wasn't more of a witness than a suspect and she possibly believed that this would get her off the hook and out of interrogation.

The third point about the police conspiracy is the most interesting. I have a huge bias against conspiracy theories. As soon as anyone starts to go "Wake up sheeple, you're being controlled." I immediately switch off. The quote you use from me at the beginning of your article is partly a reference to this. Of course you are right juries can be wrong. I just tend to think that the simplest answer is normally the best. That's it's more likely that she is guilty, than that the police dept in Italy have a massive desire to convict and innocent woman.

However on reading more about the case, I discovered that the police had a theory it was Knox, Sollecito and Knox's boss before the evidence about Guede turned up. They announced this to the world. When Guede turned up, which normally would have been the end of the case they stuck with their original theory substituting Guede for Knox's boss.
So their motive for wanting to convict Knox and Sollecito was not a conscious devious one but an unconscious subtle one. The didn't want to be embarrassed and shown to be wrong in the eyes of the world media.

Btw, this is the third time I've been proved to be wrong on the internet this week. Either I'm not a very good rationalist or I just spend to much time on the internet.

Comment author: Unknowns 14 December 2009 11:38:21AM -1 points [-]

That original theory was based on Knox's testimony-- at that point it wasn't unreasonable for the police to accept it.

Comment author: Jack 14 December 2009 01:05:43PM 2 points [-]

Unless they fed the testimony to her based on a text message that said "See you later." And frankly the conspiracy between the three of them and Knox's active participation in the murder wasn't in the testimony (as far as I can tell) she just reported recalling images of her boss associated with the screams of Kercher. At most it was just a confession to being at the scene.

Comment author: Eliezer_Yudkowsky 14 December 2009 05:16:48PM 0 points [-]

Discussion on Hacker News points to http://www.zimbio.com/Amanda+Knox/articles/58/Understanding+Micheli+2+Judge+Micheli+Rejected which is a better prosecution summary than anything else I've seen, though you've got to read Wikipedia first to know who the actors are.

Comment author: mattnewport 14 December 2009 05:25:14PM 1 point [-]

The truejustice link previously posted here was rather better formatted and appears to be the original source.

Comment author: rmattbill 15 December 2009 12:45:55AM 3 points [-]

Everyone should be aware that there are numerous errors on truejustice, and you should double check anything on there for confirmation before treating it as reliable.

Comment author: mariz 14 December 2009 07:05:02PM 1 point [-]

Posts like this are the reason I read this blog. Great job.

Comment author: AnnaGilmour 14 December 2009 07:41:08PM *  0 points [-]

There is another Occam's Razor at work here. With the blaringly obviousness of the truth of this case, how can it not be that it has been actively and intentionally ignored at best and fabricated at worst?

Comment author: AnnaGilmour 14 December 2009 07:46:14PM 1 point [-]

In other words, the Razor says that it was actively and intentionally ignored at best and fabricated at worst.

Comment author: Jack 14 December 2009 08:17:53PM 0 points [-]

I'm confused. What was fabricated at worst?

Comment author: wedrifid 14 December 2009 08:22:42PM 0 points [-]

The 'truth' (I think.)

Comment author: Jack 14 December 2009 08:32:48PM 0 points [-]

That is what the grammar of the sentence suggests, but how can the same evidence (the obviousness of the truth) indicate both that it was intentionally ignored and that it was fabricated. For that matter "the truth was fabricated" sounds like a category error to me. Truths aren't the sort of thing that can be fabricated. So I think Anna might have meant that the evidence against Knox was fabricated (or maybe the evidence against Guede).

Comment author: wedrifid 14 December 2009 08:39:15PM 1 point [-]

I concluded that she just forgot to proofread and took the meaning as "actively ignored the truth or fabricated falsehoods". (And that question is a good one.)

Comment author: AnnaGilmour 14 December 2009 08:40:08PM 0 points [-]

The case itself, that Amanda and Raffaele had any rightful place being tried. Does that help?

Comment author: Jack 14 December 2009 08:45:50PM 0 points [-]

Yeah I got it. The above went up before your clarification.

Comment author: AnnaGilmour 14 December 2009 08:28:02PM 0 points [-]

The entire case against Amanda and Raffaele.

Comment author: AnnaGilmour 14 December 2009 08:33:54PM 0 points [-]

The case for their involvement wasn't rooted in evidence or anything like evidence, so that they are obviously innocent was either ignored when this started to become clear, or the appearance of possible guilt was fabricated and known from the start that it was false.

Comment author: wedrifid 14 December 2009 08:42:50PM 1 point [-]

The case for their involvement wasn't rooted in evidence or anything like evidence, so that they are obviously innocent was either ignored when this started to become clear, or the appearance of possible guilt was fabricated and known from the start that it was false.

My impression tended towards the first of those two atrocities.

Comment author: ABranco 14 December 2009 07:52:44PM 4 points [-]

I haven't deeply read or studied the whole case itself — but by all means this is a beautiful, detailed, clearly written exposition of your train of thoughts. Thank you.

And yes, the mental suffering of spending two decades in jail + being despised by everyone around when you're actually innocent shouldn't be easy to face even with the highest possible dose of stoicism one could inject herself.

Comment author: Dagon 14 December 2009 08:39:37PM 0 points [-]

Can you show your math for your apparent belief that any murder occurred at all, and that Guédé is guilty? I'd think you'd start with similar priors (the VAST majority of people are not murdered, and the VAST majority of people do not murder others. It seems like you're giving a LOT of weight to at least some of the reported evidence or agreement about this portion of the belief.

Which evidence is this, and what is your estimate of false-positives for it?

Comment author: AnnaGilmour 14 December 2009 09:23:21PM *  0 points [-]

The material fact of a murder is the starting point for this. Then there is the material fact of Guede's DNA, and the fact of his journal, which could be used as ample evidence against him. He said his "hands were full of blood" along with interspersed memories of when he himself was hit on the head so hard as a child by his father that there was a profuse amount of blood.

Or am I missing the essence of your question?

Comment author: AnnaGilmour 14 December 2009 09:37:41PM *  -1 points [-]

The murder is an axiom (a given), as is the presence of Guede's DNA, and not only his DNA but his DNA put into context by his own written words and his verbal admission to being at the crime scene.

Comment author: AnnaGilmour 14 December 2009 09:44:36PM *  0 points [-]

That there was murder is a given since that is the reason for the investigation and trial. The presence of Guede's DNA and his own statements makes it plausible that he is guilty.

Comment author: Vladimir_Nesov 14 December 2009 09:46:39PM *  1 point [-]

The murder is a given since it the reason for the investigation and trial.

Nothing is a given if the question is about what really happened.

Comment author: AnnaGilmour 14 December 2009 09:55:05PM 0 points [-]

It is a given because for the sake of the discussion, it has been established. It is the starting point. To go back further would be unnecessary. There is ample evidence that Meredith was murdered.

Comment author: Vladimir_Nesov 14 December 2009 10:04:26PM 1 point [-]

To go back further would be unnecessary. There is ample evidence that Meredith was murdered.

Of course, but it may be a useful exercise to understand the reason for the difference in strength of this particular argument compared to the others.

Comment author: AnnaGilmour 14 December 2009 10:08:41PM 0 points [-]

I'm not sure what you mean by "the reason for the difference in strength of this particular argument..." Which particular argument?

Comment author: Vladimir_Nesov 14 December 2009 10:15:12PM 0 points [-]

The argument that there was a murder at all.

Comment author: AnnaGilmour 15 December 2009 12:13:49AM -1 points [-]

That there was a murder has been established. This is not in question due to the large quantity of evidence supporting it. The discussion is of the guilt, given the (established and known) fact of the murder. As for its usefulness, the evidence of the murder would reveal evidence of who did it, so it could be useful, but might be a moot point, since then we're already on the topic of agency of guilt.

Comment author: rmattbill 15 December 2009 12:43:08AM 0 points [-]

And let's not forget that after he fled to Germany, Guede made a phone call using his Skype account and said Knox was not at the house that night (he didn't say anything about Sollecito, has he had never even met him and didn't know what he looked like). Even after police pressured Guede to put Knox at the house, he did not. Until weeks later, when he finally changed his story and said Knox was there and had argued with Kercher about money.

Comment author: AnnaGilmour 15 December 2009 01:27:22AM *  0 points [-]

Plus, if you read Rudy's journal, you will come across red signals all over the place. He wrote that his "hands were full of blood", etc. He describes the scene as if he is in the midst of it, complete with wales (or statements, if your prefer, but it was dramatic) of guilt and remorse and recollections of his unstable childhood.

The only question is why didn't the prosecution zero in on (all) the blaring red signals regarding Rudy, and rather become hyper-focused on inconsequential faint glimmers of signals that were actually his own "psychological noise", ie reading into the situation (of Amanda and Raffaele) using inductive logic, rather than deducing from the evidence? He doesn't have any of the same obsession about or engage in name-calling of Rudy, at all. Yet, look at the swamp related to Rudy. Something is amiss.

Comment author: pete22 14 December 2009 08:52:49PM *  3 points [-]

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.

the evidence against Guédé is such that the hypothesis of her guilt is superfluous -- not needed -- in explaining the death of Meredith Kercher

I think you’re begging the question here. Those who are convinced that K&S are guilty seem to believe that the evidence from the crime scene itself suggests that Guede could not have been the only participant – i.e. his involvement does NOT completely explain the death of Meredith Kercher. They seem to believe this for two reasons:

  1. The various evidence at the crime scene itself of a clean up and/or staged break-in, things like the bra being cut off or the body being moved – hard to attribute to Guede because a. he wouldn’t have had time (is this true?), and b. little effort was taken to remove evidence against Guede himself, even very obvious things like flushing the toilet.

  2. I haven’t seen any commenters mention it here, but one of the anti-Amanda sites, in quoting the Micheli report, seemed to imply that Kercher’s injuries were inconsistent with a single attacker.

Your post appears to take for granted that these are not credible arguments, but they seem like a very significant part of the prosecution’s case – and the part that I found hardest to assess without English versions of the Micheli report and other source documents. Can you explain how you reached this level of confidence?

FWIW, I'm not an Amanda-hater …my prior probability of her guilt was 30%, and I'm ready to revise it down. I’m just not sure I fully understand your argument on this point.

Comment author: AnnaGilmour 14 December 2009 09:02:35PM *  5 points [-]

One thing to remember is that Mignini fired the coroner doing autopsy investigation when that person said it was the injuries of a single perpetrator. He then hired someone who said it was more than one perpetrator. If you would like, I can find a link to back it up. So the original report said one person caused the injuries.

Comment author: Eliezer_Yudkowsky 14 December 2009 09:16:51PM 2 points [-]

Huh. I wondered if something like this might be the case, but then wondered if I was being selectively skeptical of the prosecution and trying to dismiss all of their evidence. Next time I'll remember to (a) trust myself a little more, and (b) remember that reality itself is consistent rather than fair, i.e., Knox obviously didn't do it, thus if the coroner says it's more than one perpetrator, I should (b1) construct a model in which the coroner is pressured (or fired and redealt) and (b2) penalize the probability of that model because (hopefully) most coroners aren't pressured.

Comment author: MichaelVassar 15 December 2009 10:05:56AM 2 points [-]

I'm not sure how much hope fits into the Bayesian analysis. My impression is that doing things like pressuring coroners is routine in the US and probably in Italy as well. Of course, pressuring coroners is a special case of "doing things like pressuring coroners" and thus unlikely a-priori, but its not very unlikely a-priori and once the possibility is raised it doesn't call for much penalty.

Comment author: AnnaGilmour 15 December 2009 04:25:41PM 1 point [-]

The significant factor though is not that the coroner was fired and replaced by someone who would report multiple perpetrators. The significant factor is that the original, unprompted, unbiased, objective analysis was that it was a single perpetrator.

Comment author: komponisto 15 December 2009 02:37:50AM *  4 points [-]

The various evidence at the crime scene itself of a clean up and/or staged break-in, things like the bra being cut off or the body being moved

A bizarre or unexpected condition of the crime scene is not the explanandum here; Meredith's death is. One person is entirely sufficient to have killed Meredith, and the DNA evidence establishes with virtual certainty that Guede had the kind of contact with her necessary to accomplish this. Unless the evidence suggesting someone else was involved is of comparable power to the DNA evidence against Guede (something on the order of 30 bits), then (and this is the part people have trouble understanding) even paying attention to it at all is automatically hypothesis-privileging.

(EDIT: Eliezer corrects below. What I actually wanted to argue here was that, given the certainty of Guede's involvement, the lack of connection between him and Knox or Sollecito is strong evidence against their involvement -- probably enough on its own to outweigh the comparatively weak evidence against them provided by the alleged indications of multiple attackers at the crime scene.)

Yes, we might be curious about the unusual mechanics of the crime scene given only one person, but unless they are so strange that assuming someone else's guilt of murder (when we already have a suspect) would constitute a reasonable explanation for them, we have to regard the whole question as a distraction.

Comment author: Eliezer_Yudkowsky 15 December 2009 04:34:37AM 6 points [-]

Unless the evidence suggesting someone else was involved is of comparable power to the DNA evidence against Guede

Doesn't follow. You can have a lot of evidence for one true statement and then less evidence for another true statement.

Comment author: komponisto 15 December 2009 04:43:23AM *  0 points [-]

Not sure I understand the objection. The point is that the evidence is extremely weak by comparison; not strong enough to justify any attention.

Comment author: pete22 15 December 2009 04:47:03AM 2 points [-]

You're right, this is the part I have trouble understanding. Partly because I have trouble separating the facts of this particular case from the theoretical point you're making. So if you'll humor me for a second: let's say you're the chief of police somewhere, and one of your detectives comes back from a murder scene and tells you "we've arrested a prime suspect and we've got very strong evidence against him, including an ironclad DNA match that ties him to the murder. but we don't think he acted alone, because of X, so we want to keep looking for another suspect."

It sounds like for almost any X, your response would be "Don't waste your time. Case closed. Your hypothesis that there was another killer is unnecessary to explain the victim's death." Is that correct? What kind of X would suffice for you to let your detectives keep investigating?

Comment author: komponisto 15 December 2009 04:54:23AM *  1 point [-]

What kind of X would suffice for you to let your detectives keep investigating?

Two examples that come to mind immediately:

-Similarly incriminating DNA from someone else in addition to the prime suspect.

-Information acquired from the prime suspect himself that points to accomplices.

Comment deleted 15 December 2009 05:02:29AM [-]
Comment author: komponisto 15 December 2009 05:13:49AM 1 point [-]

Maybe. But remember that reality is consistent: If two people were at the scene committing the crime, why would there be vastly more evidence of one than the other?

Once you have the suspect, you can interrogate him to find out who he knows.

Comment author: pete22 15 December 2009 05:10:23AM 0 points [-]

That's setting the bar pretty high. What about witnesses who claim to have seen two men running from the scene, or heard multiple voices at the time of the murder?

Comment author: pete22 15 December 2009 05:11:01AM 0 points [-]

Come to think of it, why would a further (unknown) DNA sample even be enough? You've got an explanation for the crime. Surely there are far more likely priors than a double murder that would explain a second DNA sample, right? "Similarly incriminating" might not really be possible; much of what made the first sample so incriminating is that it matched a guy who you already had reason to suspect. Or did you mean that an unknown DNA sample would not suffice, only one that matched another suspect?

Comment author: komponisto 15 December 2009 05:19:00AM 0 points [-]

If the victim's body and surroundings contains DNA from two different individuals, that would suggest multiple attackers.

Comment author: rmattbill 15 December 2009 02:55:55AM 7 points [-]

"little effort was taken to remove evidence against Guede himself, even very obvious things like flushing the toilet."

The assumption here is that Knox and Sollecito carefully removed their DNA, but did not remove Guede's. Isn't the more rational explanation for all of the evidence against Guede, and the lack of evidence against K&S, that Guede did it and K&S weren't even there, as they have always claimed, and as Guede claimed no less than 5 times?

Further, there's a lot of supposition about a "clean-up" floating around on the web, but no evidence of one. There's lot of talk about bleach, bleach receipts, bleach on the knife, etc., but no evidence was introduced to support any of these claims.

Another claim is no prints were found for Knox, therefore she must've wiped them down. This presumes, incorrectly as it turns out, that no unusable prints were found. In fact, lots of smeared, smudge, or partial prints were found. The prosecution's own expert witness on fingerprints, Giuseppe Privateri, testified he saw no sign of the place being wiped down for prints. There were lots of prints, just not a lot of usable ones, which is totally normal since the way we use our hands often causes the oils left behind to be smeared.

Also, to believe this theory of a clean-up, one has to believe that with Superman-like enhanced vision, Knox and Sollecito could see their fingerprints and DNA, and Guede's, and could selectively remove their without disturbing his. This seems far-fetched in the extreme.

In the bathroom, some of Kercher's blood was found mixed with Knox's DNA, probably from splashing onto a hair follicles or dead skin cell from Knox. Why didn't this happen in Kercher's room, where the orgy took place? No intermingling of sweat, saliva, or other bodily fluids- in an orgy?!?! It boggles the mind.

Last, a lamp from Knox's room, her only source of light, was found on the floor in Kercher's room, possibly put there by Guede as he tried to look for his possessions, or look for obvious signs. If Knox so carefully scrubbed Kercher's room she was able to eras every invisible spec of DNA, why would she leave her bedroom lamp behind?

Comment author: AnnaGilmour 15 December 2009 04:23:21PM 1 point [-]

The idea of a staged break in is unsubstantiated. There is a broken window. Mignini added the interpretation without evidence of such a thing. The two shards on top of the bed turned out to be polka dots on a piece of clothing.

Comment author: AnnaGilmour 15 December 2009 04:30:21PM 1 point [-]

Something new I saw this morning. Quite incriminating of the investigation.

"Amanda Knox - Police Deceit - "Assassins" of Character" http://www.youtube.com/watch?v=AHleYhBJy8k