I don’t think you’re allowing much possibility for an innocent who has a suspicious story. You think p(guilty|incoherent) is higher than p(guilty|coherent). I agree. I’m saying that p(guilty|incoherent,criminal prosecution) is very close to the baseline p(guilty|criminal prosecution), because you only see prosecuted those cases where either the defendant is unlucky enough to have a sketchy-seeming alibi, or the direct evidence is strong enough that the alibi doesn’t matter.
Since your experience is from criminal cases, my speculation about it was inaccurate; on the other hand, that means that your experience is even less relevant than I thought. Many civil cases go to trial where, as you say, p(win) is nearly 1⁄2. Not so for criminal prosecutors; they drop cases they won’t win.
I’d like to back away from my initial response (“this is stupid”) to you.
I had understood you to be talking about personally observed frequency of (incoherent and guilty) vs. (coherent and not guilty) in the context of criminal testimony in court. Clearly that’s not the case, and you had much more experience with innocent defendants than I anticipated.
Also, I actually understood you to believe that the causation proceeded from incoherent → guilty, which of course is ludicrous. You later explained that you actually have a roughly correct causal network; my only objection would be in whether you’re using the proper frequency for (incoherent and innocent); only if it’s nearly zero can you immediately conclude that incoherence very strongly suggests guilt. (otherwise, you have to do the math).
I still hold that amongst criminal defendants at trial, (incoherent and innocent) may be quite frequent, because (coherent and innocent) are almost never brought to trial. But what’s important is, amongst criminal defendants, how much higher p(guility|incoherent,trial) is than p(guilty|coherent,trial). I don’t actually know precisely what the difference is; I also expect it to be higher, but dwarfed in importance by the additional evidence. I would be extremely hesitant to convict someone solely based on “suspicious cover-up like behavior”, but I know that it’s happened, e.g. in the case of Hans Reiser.
I would be extremely hesitant to convict someone solely based on “suspicious cover-up like behavior”, but I know that it’s happened
I also would be hesitant. And indeed, I don’t know if there was enough evidence to inculpate Knox beyond a reasonable doubt. My point in these discussions is that I’m pretty confident she was involved in the murder.
that means that your experience is even less relevant than I thought.
I would say it’s pretty relevant. I’ve questioned hundreds of people who were accused of wrongdoing; come to a belief about their guilt or innocence; and then had an opportunity to see further evidence against them and update my beliefs, so to speak.
As to your point that there is a selection bias in criminal prosecutions, that may very well be the case. I’m not sure what it implies for the Amanda Knox case. I suppose one could argue that the decision to prosecute her is evidence of her guilt. Evidence in the logical sense, not the courtroom sense.
I don’t think you’re allowing much possibility for an innocent who has a suspicious story. You think p(guilty|incoherent) is higher than p(guilty|coherent). I agree. I’m saying that p(guilty|incoherent,criminal prosecution) is very close to the baseline p(guilty|criminal prosecution), because you only see prosecuted those cases where either the defendant is unlucky enough to have a sketchy-seeming alibi, or the direct evidence is strong enough that the alibi doesn’t matter.
Since your experience is from criminal cases, my speculation about it was inaccurate; on the other hand, that means that your experience is even less relevant than I thought. Many civil cases go to trial where, as you say, p(win) is nearly 1⁄2. Not so for criminal prosecutors; they drop cases they won’t win.
I’d like to back away from my initial response (“this is stupid”) to you.
I had understood you to be talking about personally observed frequency of (incoherent and guilty) vs. (coherent and not guilty) in the context of criminal testimony in court. Clearly that’s not the case, and you had much more experience with innocent defendants than I anticipated.
Also, I actually understood you to believe that the causation proceeded from incoherent → guilty, which of course is ludicrous. You later explained that you actually have a roughly correct causal network; my only objection would be in whether you’re using the proper frequency for (incoherent and innocent); only if it’s nearly zero can you immediately conclude that incoherence very strongly suggests guilt. (otherwise, you have to do the math).
I still hold that amongst criminal defendants at trial, (incoherent and innocent) may be quite frequent, because (coherent and innocent) are almost never brought to trial. But what’s important is, amongst criminal defendants, how much higher p(guility|incoherent,trial) is than p(guilty|coherent,trial). I don’t actually know precisely what the difference is; I also expect it to be higher, but dwarfed in importance by the additional evidence. I would be extremely hesitant to convict someone solely based on “suspicious cover-up like behavior”, but I know that it’s happened, e.g. in the case of Hans Reiser.
I also would be hesitant. And indeed, I don’t know if there was enough evidence to inculpate Knox beyond a reasonable doubt. My point in these discussions is that I’m pretty confident she was involved in the murder.
I would say it’s pretty relevant. I’ve questioned hundreds of people who were accused of wrongdoing; come to a belief about their guilt or innocence; and then had an opportunity to see further evidence against them and update my beliefs, so to speak.
As to your point that there is a selection bias in criminal prosecutions, that may very well be the case. I’m not sure what it implies for the Amanda Knox case. I suppose one could argue that the decision to prosecute her is evidence of her guilt. Evidence in the logical sense, not the courtroom sense.