So making progress would probably require us to pick a small number of narrowly-defined issues to hash out, one at a time.
Sounds good, like you suggested let's cover the time of death, and also continue to go deep on the question of lab contamination.
Here's an important question to assess whether we've said anything important yet: has anything I've said surprised you?
It hasn't been predictable, but it hasn't caused me to shift significantly in favor of innocence or guilt so far. I did learn I was wrong about which knife Amanda reacted strongly to, but that's within the bounds of how many errors I expected to be making here.
I suspect I could probably get you to agree that it would be extremely unusual for no food to have passed into the duodenum 5 hours after a meal (as required by the prosecution theory), even conditioned on the already unusual fact of none having passed after 150 minutes. However, I can't predict how far you will lower your probability of guilt as a result.
I haven't looked into this much. According to Massei, Umani Ronchi, a court-appointed expert, testified that a farinaceous meal takes 6-7 hours for gastric emptying, and additionally that it's possible some of the food passed into the duodenum but then, after death, slid into the small intestine. Massei also claims that even Vinci agreed with the range of 18:50 - 4:50 for time of death. Did the defence experts take into account the composition of the meal, or testify that sliding of the food after death is unlikely?
I don't think I would have a problem positing that the expert report constitutes 50:1 evidence in favor of contamination, possibly much more.
The sample in question (Trace B) tested negative for blood, as did every other sample taken from the blade. (Samples from the handle were not tested for blood.) No attempt was made to scientifically determine the actual nature of the alleged biological material.
OK, what are the odds that a small dna trace left by "stabbing + cleaning" would test positive for blood, and what are the odds a small dna contamination to the knife would test positive for blood? (By the way, do you have a specific contamination hypothesis in mind?) In both cases, keep in mind only one "small zone" of the striation was tested for blood, and the rest of the striation was consumed in DNA analysis.
When "quantification" (test to determine whether there was enough DNA to be analyzed) was performed, Traces B and C both yielded a result of "too low". Stefanoni reported Trace B as a positive result, and Trace C as a negative result, without any justification. There is no documentation in the lab data to support her statement in court that the Trace B sample was in the range of several hundred picograms. Stefanoni also claimed to have executed steps in the quantification procedure that are not documented.
Sounds like she didn't document everything; how much are you shifting based on this? Part of the problem is I don't know how much the average technician documents, so I don't know how usual or unusual this is. If nobody documents everything, but we still see a .02/homicide contamination rate, then Stefanoni's not documenting doesn't change anything.
The "amplification" (chemical copying of the sample in order to produce a large enough amount for analysis) was performed only once, despite the fact (admitted by Stefanoni) that it should be repeated in order to be considered reliable.
Can I get a source for Stefanoni's admission? Is this from the report?
Stefanoni did not perform negative controls, which could have indicated the presence of contamination.
Is this also from the report? Have you translated this part yet?
The sample was analyzed in the same laboratory at the same time as numerous samples containing Meredith Kercher's DNA.
I gave a .05 chance that, if there was a cross-contamination, it would have been of Meredith's DNA. Are you giving a different probability?
I haven't looked into this much. According to Massei, Umani Ronchi, a court-appointed expert, testified that a farinaceous meal takes 6-7 hours for gastric emptying, and additionally that it's possible some of the food passed into the duodenum but then, after death, slid into the small intestine. Massei also claims that even Vinci agreed with the range of 18:50 - 4:50 for time of death. Did the defence experts take into account the composition of the meal, or testify that sliding of the food after death is unlikely?
We're talking here not about the time ...
Recently, on the main section of the site, Raw_Power posted an article suggesting that we find "worthy opponents" to help us avoid mistakes.
As you may recall, Rolf Nelson disagrees with me about Amanda Knox -- rather sharply. Of course, the same can be said of lots of other people (if not so much here on Less Wrong). But Rolf isn't your average "guilter". Indeed, considering that he speaks fluent Bayesian, is one of the Singularity Institute's largest donors, and is also (as I understand it) signed up for cryonics, it's hard to imagine an "opponent" more "worthy". The Amanda Knox case may not be in the same category of importance as many other issues where Rolf and I probably agree; but my opinion on it is very confident, and it's the opposite of his. If we're both aspiring rationalists, at least one of us is doing something wrong.
As it turns out, Rolf is interested in having a debate with me on the subject, to see if one of us can help to change the other's mind. I'm setting this post up as an experiment, to see if LW can serve as a suitable venue for such an exercise. I hope it can: Less Wrong is almost unique in the extent to which the social norms governing discussion reflect and coincide with the requirements of personal epistemic rationality. (For example: "Do not believe you do others a favor if you accept their arguments; the favor is to you.") But I don't think we've yet tried an organized one-on-one debate -- so we'll see how it goes. If it proves too unwieldy or inappropriate for some other reason, we can always move to another venue.
Although the primary purpose of this post is a one-on-one debate between Rolf Nelson and myself, this is a LW Discussion post like any other, and it goes without saying that others are welcome and encouraged to comment. Just be aware that we, the main protagonists, will try to keep our discussion focused on each other's arguments. (Also, since our subject is an issue where there is already a strong LW consensus, one would prefer to avoid a sort of "gangup effect" where lots of people "pounce" on the person taking the contrarian position.)
With that, here we go...