Context: I didn't know anything about the case; I think I've overheard something about it in the past, because I had a very slight sensation of déjà-vu reading your post, but I didn't really know anything. The info I used was reading the Wikipedia pages (one you linked and one on one of the trials), then skimming the sites you linked for less than a half hour.
I have reached a “decision” about it, but I didn't intend to post it. Then curiosity got the best of me and I read pretty much all the comments already here. My “estimate” wobbled a bit during the reading of the comments, but by the end it converged on its initial value. I decided to post my opinion, as somebody else mentioned, to avoid self-selection.
I used quotes above because my general state is confusion. Actually, it's confusion both about the case and about the poster's opinions (and, a bit, about your post).
The general impression I got was that all parties (except, probably, the victim) are guilty of something, including the prosecutors. But...
First, I'm not very sure exactly if your questions should be translated as “probability estimate that X killed Kercher” or not. I actually have a slight suspicion that your post might be a trick question around that. (In fact, writing now, I realize that the trial resulted in guilty verdicts on ~five counts for each, but after all the reading I have no idea what they are other than that one of each is some kind of murder.)
Regarding Knox and Sollecito, my “gut” impression is that they're guilty of something, in the sense that I'd be quite surprised if they were just two innocent people who did absolutely nothing bad (other than that joint) and got dragged in a nightmare by chance. I also have a “gut” feeling that their “guilt” is correlated.
Regarding Guede, I've got a slightly stronger gut feeling of guilt (than I do for the first two).
I also feel (as in “gut”, again) that the prosecution and trial was “wrong”. (EDIT for clarification: but I can't see any basis of estimating how wrong between “as good as reasonably possible” and “gross miscarriage of justice”.)
However, what confuses me most is the certainty of most estimates I've seen in the comments. I just don't see how one can get much farther than “I don't know, but I lean a bit towards” either way on what the posters report as their information. I mean, after only a couple hours or so of thinking (both during reading and writing this) I'm not even sure what priors might be appropriate. I feel I know so little about the case (including info like trials in general) that my response can't be more than “I don't know”. (If pressed a lot I'd output 0.5±e as a probability, simply because even my knowledge of probabilities is too weak to actually figure out if anything else would express my almost total uncertainty on this subject, and that's my cached answer for binary questions.)
Put differently, given the information I have on the subject, it feels as if the confidence I should assign to any probability estimate should be very close to 0. As I said above, I tend to give probabilities as ~50% in those cases, but that's not exactly a correct description of what I feel. A good description would be that, if forced to bet (without more time to think), I'd bet on all of them being guilty, but if given the option, I wouldn't bet any amount at 1:1 odds.
Oh, and the answer to the fourth question is very similar. Leaving aside the fact that I'm not sure exactly how I'd quantify the “coincidence” of opinions, I'm wouldn't put any significant confidence in any estimate. (The “gut” feeling is that you consider all three guilty, but that's mostly a very vague impression I got from the wording of your text rather than reasoning on my part.)
As an aside, the interesting thing about the subject is that I was surprised how little confidence I assigned to my “estimates” in this case. I usually have some opinion on most questions I encounter, but in this case I find myself really unable to arrive at one.
First, I'm not very sure exactly if your questions should be translated as “probability estimate that X killed Kercher” or not. I actually have a slight suspicion that your post might be a trick question around that
No, "X killed Kercher" is right. (Or perhaps better would be, "X participated in killing of Kercher".)
As many of you probably know, in an Italian court early last weekend, two young students, Amanda Knox and Raffaele Sollecito, were convicted of killing another young student, Meredith Kercher, in a horrific way in November of 2007. (A third person, Rudy Guede, was convicted earlier.)
If you aren't familiar with the case, don't go reading about it just yet. Hang on for just a moment.
If you are familiar, that's fine too. This post is addressed to readers of all levels of acquaintance with the story.
What everyone should know right away is that the verdict has been extremely controversial. Strong feelings have emerged, even involving national tensions (Knox is American, Sollecito Italian, and Kercher British, and the crime and trial took place in Italy). The circumstances of the crime involve sex. In short, the potential for serious rationality failures in coming to an opinion on a case like this is enormous.
Now, as it happens, I myself have an opinion. A rather strong one, in fact. Strong enough that I caught myself thinking that this case -- given all the controversy surrounding it -- might serve as a decent litmus test in judging the rationality skills of other people. Like religion, or evolution -- except less clichéd (and cached) and more down-and-dirty.
Of course, thoughts like that can be dangerous, as I quickly recognized. The danger of in-group affective spirals looms large. So before writing up that Less Wrong post adding my-opinion-on-the-guilt-or-innocence-of-Amanda-Knox-and-Raffaele-Sollecito to the List of Things Every Rational Person Must Believe, I decided it might be useful to find out what conclusion(s) other aspiring rationalists would (or have) come to (without knowing my opinion).
So that's what this post is: a survey/experiment, with fairly specific yet flexible instructions (which differ slightly depending on how much you know about the case already).
For those whose familiarity with the case is low:
I'm going to give you two websites advocating a position, one strongly in favor of the verdict, the other strongly opposed. Your job will be to browse around these sites to learn info about the case, as much as you need to in order to arrive at a judgment. The order, manner, and quantity of browsing will be left up to you -- though I would of course like to know how much you read in your response.
1. Site arguing defendants are guilty.
2. Site arguing defendants are innocent.
I've chosen these particular sites because they seemed to contain the best combination of fierceness of advocacy and quantity of information on their respective sides that I could find.
If you find better summaries, or think that these choices reflect a bias or betray my own opinion, by all means let me know. I'm specifically avoiding referring you to media reports, however, for a couple of reasons. First, I've noticed that reports often contain factual inaccuracies (necessarily, because they contradict each other). Secondly, journalists don't usually have much of a stake, and I'd like to see how folks respond to passionate advocacy by people who care about the outcome, as in an actual trial, rather than attempts at neutral summarizing. Of course, it's fine if you want to read media reports linked to by the above sites.
(One potential problem is that the first site is organized like a blog or forum, and thus it is hard to find a quick summary of the case there. [EDIT: Be sure to look at the category links on the right side of the page to find the arguments.] If you think it necessary, refer to the ever-changing Wikipedia article, which at the moment of writing seems a bit more favorable to the prosecution. [EDIT: I'm no longer sure that's true.] [EDIT: Now I think it's true again, the article having apparently changed some more. So there's really no telling. Be warned.])
After you do this reading, I'd like to know:
1. Your probability estimate that Amanda Knox is guilty.
2. Your probability estimate that Raffaele Sollecito is guilty.
3. Your probability estimate that Rudy Guede is guilty.
4. How much you think your opinion will turn out to coincide with mine.
Feel free to elaborate on your reasoning to whatever degree you like.
One request: don't look at others' comments until you've done the experiment yourself!
For those whose familiarity with the case is moderate or high:
I'd like to know, as of right now:
1. Your probability estimate that Amanda Knox is guilty.
2. Your probability estimate that Raffaele Sollecito is guilty.
3. Your probability estimate that Rudy Guede is guilty.
4. How much you think your opinion will turn out to coincide with mine.
5. From what sources you've gotten the info you've used to arrive at these estimates.
Then, if possible, do the experiment described above for those with little familiarity, and report any shifts in your estimates.
Again, everyone should avoid looking at others' responses before giving their own feedback. Also, don't forget to identify your prior level of familiarity!
If the level of participation warrants it, I'll post my own thoughts (and reaction to the feedback here) in a later post. (Edit: That post can be found here.)