But notice that these are examples of restrictions on evidence of guilt.
No, they’re not. The first one I listed can go either way.
“Since my client is a woman, you should reduce the odds you assign to her having committed a murder by a factor of 4.”
The second one can go either way too; it just as much excludes e.g. hearsay evidence that implicates someone else.
The assumption (very reasonable, it seems to me) is that human irrationality tends in the direction of false positives, i.e. wrongful convictions.
Sure, but that needs to be accounted for via the guilt probability threshold, not by reducing the accuracy of the evidence. Favoring acquittal through a high burden and biasing evidence in favor of the defendant is “double-dipping”.
If juries are capable of convicting on the sort of evidence presented at the Knox/Sollecito trial (and they are, whether in Italy, the U.S., or anywhere else)...well, can you imagine all the false convictions we would have if such rules as you listed were relaxed?
I only listed a few examples off the top of my head. The appropriate comparison is to the general policy of, per Bayesianism, incorporating all informative evidence. This would probably lead to more accurate assessments of guilt. In particularly egregious cases like K/S, it would have been a tremendous boon to them to allow them to have an explicit guilt threshold and count up the (log) likelihood ratio of all the evidence.
In any case, remember that there’s a cost to false negatives as well. Although that’s heavily muddled by the fundamental injustice of so many laws for which such a cost is non-existent.
Let me take a step back here, because despite the fact that it sounds like we’re arguing, I find myself in total agreement with other comments of yours in this thread, in particular your description of how trials should work; I could scarcely have said it better myself.
Here’s what I claim: the rules of evidence constitute crude attempts to impose some degree of rationality on jurors and prosecutors who are otherwise not particularly inclined to be rational. These hacks are not always successful, and occasionally even backfire; and they would not be necessary or useful for Bayesian juries who could be counted on to evaluate evidence properly. However, removing such rules without improving the rationality of jurors would be a disaster.
(Let’s not forget, after all, that there were people here on LW who reacted with indignation at my dismissal of certain discredited evidence in the Knox case, protesting that legal rules of admissibility don’t apply to Bayesian calculations—as if I had been trying to pass off some kind of legal loophole as a Bayesian argument. Such people were apparently taking it for granted that this evidence was significant, which suggests to me that it is very difficult for people—even aspiring rationalists—to discount information they come across. This provides support for the necessity of rules that exclude certain kinds of information from courtrooms, given the population currently doing the judging.)
Okay, then I think we’re in agreement. I guess I had interpreted your earlier comment as a much stronger claim about the mapping between pure Bayesianism and existing legal systems, but I definitely agree with what you’ve said here. I would just note that it would probably be more accurate to say that the rules of evidence are hacks to approximate Bayes and correct for predictable cognitive biases, though perhaps in this context those aren’t quite separate categories.
I think that is an incomplete description of the justification of the rules of evidence—some of these rules are also introduced to discourage particular abuses of the system, such as unreasonable searches. Otherwise, agreed.
No, they’re not. The first one I listed can go either way.
The second one can go either way too; it just as much excludes e.g. hearsay evidence that implicates someone else.
Sure, but that needs to be accounted for via the guilt probability threshold, not by reducing the accuracy of the evidence. Favoring acquittal through a high burden and biasing evidence in favor of the defendant is “double-dipping”.
I only listed a few examples off the top of my head. The appropriate comparison is to the general policy of, per Bayesianism, incorporating all informative evidence. This would probably lead to more accurate assessments of guilt. In particularly egregious cases like K/S, it would have been a tremendous boon to them to allow them to have an explicit guilt threshold and count up the (log) likelihood ratio of all the evidence.
In any case, remember that there’s a cost to false negatives as well. Although that’s heavily muddled by the fundamental injustice of so many laws for which such a cost is non-existent.
Let me take a step back here, because despite the fact that it sounds like we’re arguing, I find myself in total agreement with other comments of yours in this thread, in particular your description of how trials should work; I could scarcely have said it better myself.
Here’s what I claim: the rules of evidence constitute crude attempts to impose some degree of rationality on jurors and prosecutors who are otherwise not particularly inclined to be rational. These hacks are not always successful, and occasionally even backfire; and they would not be necessary or useful for Bayesian juries who could be counted on to evaluate evidence properly. However, removing such rules without improving the rationality of jurors would be a disaster.
(Let’s not forget, after all, that there were people here on LW who reacted with indignation at my dismissal of certain discredited evidence in the Knox case, protesting that legal rules of admissibility don’t apply to Bayesian calculations—as if I had been trying to pass off some kind of legal loophole as a Bayesian argument. Such people were apparently taking it for granted that this evidence was significant, which suggests to me that it is very difficult for people—even aspiring rationalists—to discount information they come across. This provides support for the necessity of rules that exclude certain kinds of information from courtrooms, given the population currently doing the judging.)
Okay, then I think we’re in agreement. I guess I had interpreted your earlier comment as a much stronger claim about the mapping between pure Bayesianism and existing legal systems, but I definitely agree with what you’ve said here. I would just note that it would probably be more accurate to say that the rules of evidence are hacks to approximate Bayes and correct for predictable cognitive biases, though perhaps in this context those aren’t quite separate categories.
I think that is an incomplete description of the justification of the rules of evidence—some of these rules are also introduced to discourage particular abuses of the system, such as unreasonable searches. Otherwise, agreed.