One of the most enjoyable things about economic analysis is that it often yields surprising facts about cherished institutions. For example, the jury selection process in the United States probably burdens defendants disproportionately in criminal trials – most people believe jury selection serves to mitigate the problem of biased juries.
Why? Imagine the distribution of jurors by how sympathetic they are to the defendant. I would guess the distribution isn’t normal with a mean of “indifferent”; instead, the average juror probably starts from a relatively unsympathetic position. Assume for a particular defendant, 60% of the population has some bias against the defendant and 40% has some bias in favor. If the jury is randomly selected, we would expect 6/10 jurors to be relatively anti-defendant. If the prosecutor and defense attorney can identify the jurors biases and are allowed one challenge each, the final jury should be 6.2/10 anti-defendant. Every additional challenge increases the frequency of anti-defendant jurors in the panel.
Apparently Scots law embraces (wisely, I think) random jury selection. The quotation below is from Peter Duff’s “The Scottish Criminal Jury: A Very Peculiar Institution”:
There is no equivalent to the voir dire procedure in Scotland, a fact which might surprise some American readers. The strong opposition of the Scottish criminal justice system to any procedure of this type is well illustrated by the observations of the Appeal Court in McCadden v. H. M. Advocate:
There may never be a process which eliminates the possibility of personal prejudices existing among jurors, the nearest practical one (and it is not foolproof) being possibly the “vetting” of jurors, a system against which the law of Scotland has steadfastly closed the doors. Evidence of how it is used and abused in countries in which it is operated only tends to confirm the wisdom of that decision.
The court went on to observe that it should not be “lightly assumed” that jurors will pursue their prejudices in defiance of their oath and the directions of the judge. On a more practical note, the court pointed out that the broad base from which jurors are drawn means that any prejudices and biases tend to cancel each other out, and further, that the majority verdict, whereby a bare eight to-seven vote either way suffices, ensures that it is unlikely that one prejudiced juror can affect the outcome of the case.