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Sebastian_Hagen comments on The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom - Less Wrong

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

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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: Questor 16 December 2009 02:07:44AM 4 points [-]

Low copy number Test... you left out that there are very few labs certified as being acceptable to do that test which is still regarded as experimental and in the UK there is a stringent set of minimum standards for equipment, procedures for the lab itself not to mention the person doing the test. Would you be surprised to hear that the lab that did the test did not meet these requirements in the slightest? It may also be true that though equipped for standard DNA tests was not technically certified at the time even for that? An expert who is convinced the results are reliable when she had never done this type of test before using equipment not designed or set up for such extreme amplification plus leaving out the other calibration tests and tests on a control and not releasing a lot of other details of what she did. She is an employee of the Italian Government just like the prosecutor who unlike many other systems also runs or in this case directs the investigation. The results on the Bra clip and the knife blade are not scientifically usable and should never have been accepted as reliable evidence. This is in the realm of pseudo science. these links have all the details http://freeaman.001webs.com/pdfs/LCN_DNA_I.pdf http://freeaman.001webs.com/pdfs/Methods_of_the_Polizia_PseudoScientifica.pdf The same with pictures and video http://www.sciencespheres.com/2009_10_01_archive.html And New Scientist Magazine has an article about concerns that world experts in DNA testing have. http://www.sciencespheres.com/2009_10_01_archive.html http://freeaman.001webs.com/pdfs/LCN_DNA_II.pdf All of this leaves 2 key bits of evidence, the only 2 alleged to link AK or RS to the crime scene... revealed to not be credible evidence at all no matter what the prosecution expert(s) said about it

This blog is great... the lead post does a good job of showing that the theory came first before any evidence and all the efforts since then have been aimed at proving the originally baseless theory which was based on pop psychology disguised as some sort of science...Dietrologia combined with a casual hunch driven version of BIA Behavioral Interview analysis. http://deception.crimepsychblog.com/?p=78 And just this short clip of Giobbi, the lead investigator at the start... is just about the best encapsulation of the mindset that originated and drove the entire wrongheaded prosecution. THEORY First , evidence after... http://www.youtube.com/watch?v=sWkZPWRS3N0&feature=PlayList&p=A24DFCC06CD8360D&index=0

Comment author: Sebastian_Hagen 16 December 2009 02:23:03PM 1 point [-]

Very interesting reports about the LCN analysis performed in this investigation; I hadn't come across those before (FOA doesn't seem to link to them). This diminishes my confidence in those results meaning much of anything significantly. Thanks!

Comment author: pataz1 16 December 2009 11:46:32PM 0 points [-]

The problem for the trial was the Defense's argument against the DNA on the knife was undermined by Sollecito admitting there may be the victim's blood/dna on the knife because of a dinner at his house that never happened. Although it tested negative for blood, at that point, the critique against the LCN DNA on the knife is almost superfluous. Sollecito made up a reason to excuse evidence that the defense was challenging the proof of.

Comment author: McJustice 02 January 2010 11:20:05PM 2 points [-]

About LCN DNA... only the UK currently approves that kind of evidence in a trial BUT they have an extremely strict set of standards on how to run those kinds of tests AND require a very expensive specially built and equipped lab. There are very few DNA labs in the entire world that comply. And there are not many properly trained "experts" who are certified to carry it out. I should mention that none of those labs happen to be in Italy and the Italian technician was not trained or certified to do it. Also her boss in the lab worked as a paid consultant for Mignini at times and there is the implication that she was under the gun to come up with results.

All her original DNA tests showed no DNA on the knife at all. Only when she circumvented the built-in limits in the equipment and without doing any of the recommended calibration for false positives and running a lot more amplification runs did she finally come up with partial matches in a very statistically noisy result. And even then great care must be taken in interpreting the results which are much more liable to contamination than standard DNA tests. And even at this point the results with her "interpretation" of the results only yields suggestion of Meredith's DNA... not blood. And this is important: If the knife was cleaned with bleach there would be no DNA but blood would still be detectable. And blood was not detected. The test for blood is very sensitive and it is very hard to eliminate all blood traces and yet there was no blood. That implies strongly that whatever DNA was detected was contamination and a weak result open to interpretation. Her DNA test reports as presented to the court are not complete so the entire process she used for all of these key tests is not available for review. Additionally the court did not allow defense DNA experts to testify about the faults in the prosecution's DNA evidence.

Italian judges have poor understanding of forensics and tend to accept unquestioningly the results of government forensic labs.

http://www.foreignpolicy.com/articles/2009/12/10/can_anyone_get_a_fair_trial_in_italy "For one, they say that coerced confessions and the use of dubious forensic evidence, as might have happened in the Knox case, are way too common. "Inquiries are conducted without any reliable methods," says Roberto Malini, president of EveryOne, a nongovernmental organization that defends ethnic minorities in jail. "Tests take place solely in the laboratories of the state police. There's no independent lab, and independent observers do not have access to the police's work."

"Legal experts also share concerns about Italy's bar for admissibility. Il Giornale, a conservative newspaper, for instance, recently published an interview with Marco Morin, a Venice-based firearms expert who declared he no longer wanted to work in Italian courts. "In the United States, federal judges must study a 637-page manual in order to be able to evaluate [forensic] evidence," he told the newspaper. "Here, they accept everything without questioning, as long as it comes from the institutional laboratory."