[This is a passage I just wrote for a chapter of my current book project, Legal Systems Very Different from Ours. I thought my blog readers might find it of interest.]
People in the past worried about convicting the innocent too. In the early Middle Ages, they had a solution–let God judge. A defendant could be subjected to an ordeal, such as plunging his hand into boiling water, carrying a red hot iron, being dumped bound into water. Various passages in the Bible were interpreted to imply that God would reveal guilt (hand injured or body sank) or innocence (not injured, floated). Since God was omniscient, it was an approach that guaranteed a correct verdict.
The use of ordeals was eventually abandoned on theological grounds. A more careful examination of the biblical passages found little support for it, and it could be viewed as an attempt by humans to compel God to serve them, religiously dubious. In 1215, the fourth Lateran council rejected the religious legitimacy of judicial ordeals and banned priests from participating in them. Over the next few decades most European countries abandoned their use.
That left medieval judicial systems with the problem of finding another way of being certain a defendant was guilty. The solution was to impose a very high standard of proof, evidence “clear as the noonday sun.” Conviction required either two unimpeachable eyewitnesses to the crime or a voluntary confession. Circumstantial evidence, however strong, was insufficient.
In the history of Western culture no legal system has ever made a more valiant effort to perfect its safeguards and thereby to exclude completely the possibility of mistaken conviction. But the Europeans learned in due course the inevitable lesson. They had set the level of safeguard too high. They had constructed a system of proof that could as a practical matter be effective only in cases involving overt crime or repentant criminals. Because society cannot long tolerate a legal system that lacks the capacity to convict unrepentant persons who commit clandestine crimes, something had to be done … .(Langbein 1978)
The solution was the law of torture. Once the court had half-proof, one eyewitness or the equivalent in circumstantial evidence, the defendant could be tortured into confessing. A confession under torture was not voluntary, but that problem could be dealt with. Stop the torture and the next day ask the defendant if he is still willing to confess. Since he is now not being tortured, the confession is voluntary. If he doesn’t confess, torture him again.
John Langbein, my source for this account, offers a parallel story in modern law. Two hundred years ago, jury trials were short:
In the Old Bailey in the 1730s we know that the court routinely processed between twelve and twenty jury trials for felony in a single day. A single jury would be impaneled and would hear evidence in numerous unrelated cases before retiring to formulate verdicts in all. Lawyers were not employed in the conduct of ordinary criminal trials, either for the prosecution or the defense. The trial judge called the witnesses (whom the local justice of the peace had bound over to appear), and the proceeding transpired as a relatively unstructured “altercation” between the witnesses and the accused. In the 1790s, when the Americans were constitutionalizing English jury trial, it was still rapid and efficient. “The trial of Hardy for high treason in 1794 was the first that ever lasted more than one day, and the court seriously considered whether it had any power to adjourn… .”
Over the years since, trials have become longer and much more complicated, at least in part to reduce the risk of convicting the wrong person. Patricia Hearst’s trial for bank robbery lasted forty days. That was unusually long, but the average felony jury trial in Los Angeles in 1968 took 7.2 days, more than a hundred times the length of a felony trial in the Old Bailey in the 1730’s. If every felony conviction in the U.S. took that long, felony trials alone would require the full time efforts of more than the total number of judges in the state and federal systems. Also the full time efforts of close to a million jurors, court attendants, and the like. Not impossible, but very expensive.
The American legal system found a less expensive alternative. Like its medieval predecessor, it substituted confession for trial. The medieval confession was motivated by the threat of torture. The modern version, a plea bargain, is motivated by the threat of a much more severe sentence if the defendant insists on a trial and is convicted. Like the medieval version, it preserves the form–every felony defendant has the right to a jury trial, a lawyer, and all the paraphernalia of the modern law of criminal defense–while abandoning the substance. Conviction after a lengthy and careful jury trial is, arguably, evidence of guilt beyond a reasonable doubt. The willingness to accept a sentence of a year, possibly a year already served while awaiting trial, instead of the risk of ten years if convicted is not.
 In the U.S. in 2006, an estimated 1.2 million persons were convicted of a felony. If each of them had had a jury trial of 7.2 days the total would have been 8.6 million trial days. Assuming that courts function five days a week, 52 weeks a year, felony cases alone would have required the full time effort of 33,000 judges. Add in a few more for the trials of defendants who were acquitted. There are about 30,000 judges in the state judicial systems, and another 1,700 in the federal system.