

The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom - rms
http://lesswrong.com/lw/1j7/the_amanda_knox_test_how_an_hour_on_the_internet/

======
heyitsnick
The media has truely outdone itself is mis-reporting this case, and sadly this
article - surprisingly for one focused on rational thought - is no exception.
There is a body of hard evidence, including forensic, such as (but not an
exhaustive list):

\- 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.

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.

This is an English translation of the judge's summary:

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

Other links:

[http://truejustice.org/ee/index.php?/tjmk/comments/how_the_m...](http://truejustice.org/ee/index.php?/tjmk/comments/how_the_media_should_approach_the_case_if_justice_is_to_be_done_and_seen_to/)

[http://www.truejustice.org/ee/index.php?/tjmk/comments/why_d...](http://www.truejustice.org/ee/index.php?/tjmk/comments/why_defendants_mostly_dont_testify_those_devils_that_lurk_in_the_details/)

[http://truejustice.org/ee/index.php?/tjmk/comments/highlight...](http://truejustice.org/ee/index.php?/tjmk/comments/highlights_of_the_testimony_on_6_february_and_7_february/)

[http://www.timesonline.co.uk/tol/news/world/europe/article36...](http://www.timesonline.co.uk/tol/news/world/europe/article3629353.ece)

[http://www.guardian.co.uk/world/2009/feb/08/kercher-trial-
kn...](http://www.guardian.co.uk/world/2009/feb/08/kercher-trial-knox)

edit: I left out a few other key points to the prosecutions case:

\- 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.

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.

This article touches on little of these facts.

~~~
davidw
I think they were involved in it, but doesn't a murder conviction usually
require proof that person X actually did the killing? Otherwise it's accessory
to murder or something.

BTW, what a lot of people are saying in Italy is that she'll probably be let
off on appeal.

~~~
patio11
_I think they were involved in it, but doesn't a murder conviction usually
require proof that person X actually did the killing?_

That depends on your jurisdiction. I'm not familiar with Italy, but most U.S.
states and the federal government do not require actually personally causing
death as an element of the crime of murder. If you're a) engaged in the
commission of a felony (sometimes, an enumerated list of "really bad
felonies") and b) someone dies with cause proximate to the felony you're
committing, you just earned yourself a murder charge, regardless of who pulled
the trigger. This is called "felony murder". The most common use case is
suspects A, B, and C attempt armed robbery on D, D dies in the attempt, and A,
B, and C each admit to the robbery but not to the killing. Absent the felony
murder theory, you might have to sift through confusing physical evidence and
unreliable testimony of self-interested shady characters. With felony murder,
your options are simpler: charge 'em all.

~~~
DenisM
I think there is another reason for this practice:

Imagine that one criminal has good leadership skills and is able to manipulate
another, weaker criminal. He could then convince the weaker criminal to pull
the trigger and escape consequences himself, and then do it again and again
with different weak criminals. By sharing the blame the system compels the
leader, whoever he is, to restrain the underlings rather than push them to the
extreme.

------
herdrick
The point of the post on lesswrong.com is that since it's agreed that Guede
murdered the victim, you have completely explained away the murder. So now you
must start over, from scratch, as if the victim were still alive, and ask how
likely it is that Knox and Sollecito killed _somebody_ based on the other
evidence: that both lied repeatedly to the police, that there was only one
good fingerprint of hers within her own apartment, that she uses bleach to
clean her apartment, and so on. Taking that evidence by itself - without any
dead or missing person, mind you - would you even accuse them of anything more
serious than obstructing the police?

And yes, the priors - like the probability that a 20 year old female college
student with no history of violence or mental disturbance of any kind would
commit a murder - are certainly very relevant. That is one of the least
violent categorizations of humans you can create. (In fact a more accurate
prior would be even more miniscule: the probability that such a person would
lead an elaborate team sex murder, an act so rare there is no term for it.)

(However, there is some other evidence that is hard to deal with in this
model, like the crime lab saying that there is Knox DNA on the bloody bra
clasp of the victim. That evidence seems hopelessly entangled with the murder.
How can this model be used to reason about it?)

Anyway, all I know of the case is what other commenters here and the OP on
lesswrong.com wrote, so my facts are suspect. I've just tried to explain what
the OP is saying. Did I succeed?

~~~
rms
I think you did, and it's important to say that the Less Wrong OP has just
made one of many different cases for why reasonable doubt exists. This
approach was not used at the trial because the defense argued the version of
the truth that Knox and Solecito tried to create.

~~~
herdrick
Glad to hear it.

The OP would say that his framework is the only rational one.

~~~
rms
Probably. If so, I'd like to hear how his idealized Bayesian system of justice
works.

The legal system doesn't work on Bayesian analysis. It has a probability
system defined based on the meaning of English words...
[http://en.wikipedia.org/wiki/Burden_of_proof#Standards_for_d...](http://en.wikipedia.org/wiki/Burden_of_proof#Standards_for_detentions.2C_searches.2C_arrests_or_warrants)

------
citatus
As computer people, scientists etc you should all be aware of the dangers of
untrained outsiders who believe that they can not only understand a complex
field with a minimum of logic, rationality and commonsense but understand it
better than the trained professionals in that field. As a practicing lawyer,
this analysis really sounds to me like the analysis of an intelligent climate
skeptic or an intelligent arts graduate sounding forth on AI.

Criminal justice systems are hard. They're right up their with the hardest
things humanity has to deal with. They deal with ambiguous facts, necessarily
inadequate rule systems and with intelligent human actors constantly trying to
game the system - what's more the stakes are terrifyingly high, up to and
including the life or death of the participants.

Sure, errors tragically occur. But we should really pause before pronouncing
--- based on Bayes, blogs and journalists --- that the cursory judgement of a
non-profesional who wasn't in the court is superior to the considered
judgement of judge and jury made in full cognisance of the likely outcome of
conviction after listening to all the evidence including first hand witness
testimony.

And no, throwing in an offhand comment about how Occam's razor disproves God
and therefore a little logic wielded with "courage and a certain kind of
ruthlessness" enables superior thinkers to do better than the hidebound judge
and jury (who were probably irrational Christians anyway) doesn't make the
argument any more convincing.

------
ezy
e.g. A bunch of people debate "rationality" using a few "priors" based on
flimsy evidence from the internet. Just because you can use Bayesian
nomenclature to snow others, doesn't make it rational. This whole thing hinges
on the priors, and the author has given very weak evidence for them.

~~~
frisco
The whole thing doesn't hinge on the priors: the priors should be rather easy
to agree to (i.e., the observable rate at which the general population in
Amanda Knox's relative bucket commit murders). The author's entire point is
that all of the evidence presented against Ms Knox is irrelevant because the
bar for it to be incriminating is way high given the evidence against Guede
(and it doesn't meet that bar).

~~~
ezy
This doesn't make sense. For two reasons.

(a) It isn't zero-sum. Guede was convicted -- he is guilty, he did it. What we
are determining is whether he acted alone.

(b) The priors are crap because they are weak, not because they are agreed
upon. This is just a model, and it feels to me that the author is overfitting.
The prior you mentioned as an example is so far away from the case at hand to
be virtually useless.

~~~
frisco
So, you're right in that Guede being guilty doesn't imply that Knox isn't.
But, the evidence against him affects how the evidence against Knox has to be
handled: for example, the lack of physical evidence against Knox becomes a big
deal when Guede leaves tons of it. Re: priors being far away: a prior is the
probability of an event occurring before _any_ evidence has been observed.
Priors are always necessarily that far removed; those are the correct priors.

~~~
ezy
Fair enough, I could see relative evidence being used as evidence. :-) I think
that negates my first point, you are correct.

But I strongly disagree on your understanding of the impact of priors. There
are several ways to look at it, all equivalent. The easiest is the single
prior: Did she do it? None of us are psychic, so that isn't helpful, 'cause we
cant estimate it at all. We have to break that down into some of its
components.

In fact, your argument (which I totally agree with, BTW) is based on a very
specific prior: that in cases with this kind of relative imbalance of
evidence, there is a high prob that one party is guilty and the other isn't
(or some such, I may not be stating it as specifically as I should be).

All the evidence presented has it's own implied priors, and the right
combination of evidence has it's own prior, etc. These all need to be combined
with weights based on other priors. Since noone can compute _all_ of these
priors in the space of one hour, that makes it all a _judgment call_ , not a
rational decision.

And this is where I think the post's pontificating gets it terribly wrong.
There's nothing rational at all about the process, other than you're
attempting to blindly apply the Bayesian formula.

~~~
frisco
Ok. I agree with you that the post was confused and kind of incoherent at
times. It was somewhere deep in it I ended up seeing what the author was
talking about (taking his statements about physical evidence on faith for the
sake of discussion). I'm definitely not saying that Ms Knox is innocent -- I
don't know anything about the facts of that case, so we're only talking about
the mathematical methodology here.

I do think your definition of a prior is a bit off though... like, the choices
around priors wouldn't be whether to use "did she do it" vs the imbalances of
evidence or such. We're trying to estimate the likelihood of "did she do it,"
so the question is what do we use to do that? The prior probability of "she
did it" has to be the probability that some random member of the
20/female/american/student general public will commit the murder, because we
don't have anything more than that (as you said). Then, we update our estimate
by looking at the available evidence (such as, "was found standing by door
holding bleach mop," which would the viewed in terms of the likelihood that
that would be observed and the statement 'she did not do it' being true) to
come to our posterior probability, which is the estimate informed by all of
the available evidence.

As a side note, it's great when you can have a civil discussion on the
internet. Maybe there's hope for HN after all.

------
antirez
You can say everything about Italy, but not that our juridical system is
broken in this way: it's much better than USA system in preventing innocent
people from going to jail. There are three levels of giudice, and every level
can only give you a penalty <= the previous one, and if there aren't _many_
strong proofs it's likely you will not get marked as guilty. Also there is no
such "popular jury", it's all made by professional people. We are mostly an
irrelevant nation lately, but 2500 years of history of our juridical system
are still in action.

