ciphergoth comments on You Be the Jury: Survey on a Current Event - Less Wrong

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

You are viewing a comment permalink. View the original post to see all comments and the full post content.

Comments (260)

You are viewing a single comment's thread. Show more comments above.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

What fraction of convicts are eventually proven innocent?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Comment author: Morendil 10 December 2009 08:04:06PM 0 points [-]

How do you get that figure ?

It seems even harder to estimate the rate of "cause celebre wronful convictions" than to estimate wrongful convictions in general.

Moreover, I'd be concerned that this particular reference class leaves you vulnerable to availability bias. You're more likely to remember cases where a convicted person was eventually proven innocent; we never see newspaper headlines proclaiming "Conviction of X still not overturned".

Comment author: ciphergoth 10 December 2009 09:11:24PM 0 points [-]

The one big example that comes to my mind of a cause celebre conviction that turned out to be proper is Alger Hiss, though I note from Wikipedia that many still dispute his guilt.

Comment author: Jack 10 December 2009 09:15:03PM 0 points [-]

Also, in general, the Communist Party USA really was trying to get secret allies in high government positions and really was under the control of Soviet intelligence.

Comment author: ciphergoth 14 December 2009 08:47:52AM 0 points [-]

Genuine question: were there a lot of people who were not supporters of the CPUSA but who argued that one or both of these were not true?