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...
Surely you meant the defense appeal document here? (I haven't referenced the prosecution appeal, and there wouldn't be much reason to, since it's just a 20-page rant arguing that Amanda and Raffaele are really nasty people and deserve a harsher sentence than the Massei court gave them.)
My interpretation of Ronchi doesn't depend on the defense appeal; it's simply the common-sense default meaning of what he said, as reported in Massei-Cristiani, and confirmed by general information about average gastric emptying times.
But even if it did, the appeal documents constitute the defense's reply to the Massei-Cristiani report, and so I don't see why they are any less useful than the latter. They rely on the same records that Massei and Cristiani do.
Interestingly, p. 390 says the opposite: that Meredith had not consumed alcohol, according to Lalli. (And indeed it has been suggested by others elsewhere that the alleged small gastric alcohol level could have been due to a fermentation reaction). However, this is unlikely to be an important issue, as you point out.
Of course, this is not the only internal contradiction in the document:
Indeed, it seems the only way to know for sure which of these passages (if either) is accurate would be to have a transcript of Introna's testimony, which we unfortunately don't have. However, it's pretty clear in any case that Introna would exclude the Massei timeline of post-23:00.
I would sooner hypothesize that Meredith's last meal actually took place closer to 19:00 than 18:00, given the vagueness of the testimony on the matter. This puts her within 2 standard deviations, perhaps even 1.5.
But, granting a non-normal distribution, it's really difficult for me to see how it could significantly work against Raffaele, given where the 25th and 75th percentiles are. Probability mass would have to be transferred to the extreme right tail from somewhere else; how do you propose to do this in a way that isn't specifically tailored to yield the desired bottom line?
My questions, in that case, are:
(1a) What does your gastric lag-time model look like, such that you don't get significantly more surprised by going out to 22:00 than 21:00?
(1b) Why do you believe that model rather than one more similar to mine?
(2) What is your probability of guilt, conditioned on death having occurred (a) before 21:30? (b) before 22:00?
Slippage is a priori unlikely, especially with the ligatures applied (professional opinion), and hence given a level of gastric contents consistent with the meal in question, there's no reason to believe any significant slippage occurred.
Only with regard to fried food being the cause; as you'll recall I've already allowed for a total emptying time of 6-7 hours "in some circumstances". Note that this timeline is characterized as "markedly delayed" by the authors. And, once again, the relevant variable for us is lag time, not total emptying time. (If we try to extrapolate, using the fact that 1/2 seems to be an upper bound on the ratio of lag time to total emptying time, with 1/3 being in practice a better estimate, this would yield no more than 158.5 minutes, and probably something more like 105 minutes, in this "markedly delayed" scenario.)
The lag time given in the alcohol study you linked to is 48.1 ± 6.5 minutes (!). (And note this: "The lag phases after 4 and 10% (v/v) ethanol, beer, and red wine were not significantly different from that of water... the inhibitory effect of ethanol and alcoholic beverages is mainly induced by a prolongation of the gastric emptying phase (without affecting the lag phase)...")
Here is another source characterizing any lag time over 150 minutes as "extremely delayed". By comparison, "normal" is 50-100 min and "delayed" is 100-150. For half-emptying time, over 200 minutes is "extremely delayed".
Just how large do you think the standard deviation is? If you believe in the Massei theory, you have to come up with a lag time of four hours at minimum. I can't find any evidence that that is anywhere close to being within normal human parameters. Can you?
In my view, essentially all of the uncertainty arising from the factors you mention is used up simply by postulating a lag time of two hours or more, in contrast to the more typical 50-100 minutes. This view is supported by the sizes of the standard deviations relative to the means in all of the various studies.
On the other hand, if you want to believe the time of death was earlier, you run into other problems (in addition to the improbably extreme lag time for anything after 22:00). From 22:30 onward there was a broken-down car outside the cottage, with a tow truck arriving at around 23:20-23:30. No one associated with this incident (occupants of the car, tow-truck operator, a street witness) reported seeing anyone enter or exit the cottage, or hearing anything coming from inside. (This is of course also a problem for the Massei timeline.) There was activity on Meredith's cell phone at 21:58, 22:00, and 22:13, making it unlikely that death occurred between these times. (Incidentally, it's worth noting the interrupted call home at 20:56, not attempted again afterward, which is extremely consistent with the defense theory of when the attack occurred.) And then, of course, there is the computer activity at 21:10 and (according to the defense) 21:26.
So what is your probability distribution for time of death?
If we model the meal start-time as a normal distribution, then it'll be simple to add it to the model and combine it with the other sources of uncertainty, since two normal distributions sum to a new normal distribution with a variance equal to the sum of the variances. Though now that I mention it, a lot of the other bits of uncertainty might... (read more)