I find “beyond reasonable doubt” rational, in principle - the devil is what people consider “reasonable doubt” of course.
This is a complex issue, from a practical perspective. I believe that the philosophical matter is very simple – you must be certain that the accused did the deed. Empirically, it is well-established that the prevailing US jury instructions on burden of proof fail to communicate what must be communicated. Here is a sample of the problem. In Cage v. Louisiana, 498 U.S. 39 (1990), the trial court instructed that:
[A reasonable doubt] is one that is founded upon a real tangible substantial basis and not upon mere caprice and conjecture.
It must be such doubt as would give rise to a grave uncertainty
, raised in your mind by reasons of the unsatisfactory character of the evidence or lack thereof. A reasonable doubt is not a mere possible doubt.
It is an actual substantial doubt
. It is a doubt that a reasonable man can seriously entertain. What is required is not an absolute or mathematical certainty, but a moral certainty.
This is way wrong (as was determined on appeal) – it requires establishing grave and substantial doubt. It simply misstates the burden of proof, imposing an unconstitutional affirmative burden on the defense.
The must successful approach states the burden of proof (BOP) in terms of the state’s obligation to prove something. That specifically refers to a doubt grounded in a concrete, unanswered fact. Thus arbitrary and imaginary claims to not constitute “doubt”; but if there is weak evidence (real i.e. unrefuted evidence) that constitutes support for a claim of an alibi, then there is a concrete unanswered fact that constitutes “doubt”.
A serious problem with current instructions is that they lead jurors to believe that once the prosecution has advanced some incredibly weak claim, it is the duty of the defense to refute that claim. I think one reason this happens is that jurors are told to make a decision between “guilty” and “not guilty”. The problem is how people are likely to interpret that two-way choice. If the alternative were between “proven guilty” and “not proven guilty”, there would be fewer convictions in questionable cases. As it is, instructions don’t clearly tell jurors that “if you are not completely certain, vote ‘not guilty’”. An example of an empirical finding on this point, about 30% of jurors polled in Wyoming agree that when the state gives some evidence of guilt, the defense must then persuade the jury of his innocence. (This is false, w.r.t. what the BOP instruction is supposed to have jurors thinking).
The Federal Judicial Center instructions address this, more satisfactorily, with the recommended instruction “A reasonable doubt may arise from the evidence itself or from a lack of evidence”. There are various empirical studies that show that this kind of instruction plus a re-statement of what the state must do – leave the juror “firmly convinced” – substantially reduces the percentage of improper convictions.
There are some important linguistic effects pertaining to the expression “beyond a reasonable doubt”, which has become common in jury instructions. The noun “doubt” can refer to the mental state of having a certain propositional attitude, or it can refer to a piece of evidence against a proposition. If you use “reasonable doubt” as a mass noun, it refers to a mental state, and if you use “reasonable doubt” as a count noun, then it refers to pieces of evidence. The current expression “proof beyond a reasonable doubt” treats “doubt” as a count noun, which means that, if you think you have “a reasonable doubt” you must ask “what are they” (the pieces of evidence), which means that the defense must provide doubts.
Now finally, here is why every juror should be forced to read OPAR ch. 5. Recall that the strongest mental state is that you are certain, that the evidence is sufficient to prove the conclusion, and that there is no evidence to suggest otherwise. You could also disbelieve, because there is very strong evidence showing that the proposition is actually false – thus “be certain that it is not the case”. In the middle but towards the certainty end, you could strongly suspect that a proposition is true. Even earlier on the Peikovian evidentiary scale, towards the disbelief end, you may have some evidence indicating that the claim is true but more evidence that it is false, so you doubt the claim.
As you can see, “doubt” is a fairly active state of disbelief. But this is the wrong end of the scale for a juror to be on. It is not the burden of the defense to so totally overcome the arguments of the prosecution that the juror does beyond saying “The prosecution’s claim is only weakly possible, in fact the claim is arbitrary”. By demanding the creation of “doubt”, the defense is put in the position of having to prove the falsity of the prosecution claim.
So the focus should be on requiring the prosecution to provide actual evidence of guilt to the point that the juror is certain that the claim is true.