A new study reports that there are probably thousands of innocent people in prison. The leading cause of false conviction in rape cases is misidentification by witnesses. The leading causes of erroneous conviction in murder cases are (1) false confession and (2) perjury. False confession is far more common than people believe, medicine more common than common sense would suggest. There needs to be more scientific study on the phenomenon of confession, particularly among children and the mentally retarted.

Perhaps there also need to be more thinking about whether cross examination works. This study suggests that cross examination falls short a significant amount of the time, both in cases where the witness is mistaken and where the witness is lying. I have heard cross examination called the most potent tool devised by humans for the ascertainment of truth. That certainly has not been my experience with it, and I think that’s probably true most of the time for most attorneys, though we are disinclined to say so, lest someone say that we simply don’t wield the tool that well. Our allegience to this blunt tool may simply be because there’s nothing better that we have developed over the years.

A policy question remains. How many false positives (i.e. false convictions) is society willing to tolerate to have an otherwise functional justice system? One District Attorney quoted in the New York Times article on this study said “We all agree that it is better for 10 guilty men to go free than for one innocent man to be convicted. … Is it better for 100,000 guilty men to walk free rather than have one innocent man convicted? The cost-benefit policy answer is no.”

I, of course, think that’s wrong. Criminal prosecution destroys a person’s life and family. If an error can be prevented, it should, and if an error occurs as a regular function of the system, e.g. by relying on unreliable evidence like uncorroborated confession, then the system should change.

But I wonder whether society agrees with me or with the D.A. quoted above? On one hand, people seem very willing to accept some rate of error, even in the most important of endeavors, like voting. Even in the area of medical malpractice, most people who are injured by some kind of mistake do not sue, they just deal with the problem. Perhaps this is why there has been so little public fear and outcry about the detention of Jose Padilla and Yasir Hamdi.

Padilla and Hamdi’s cases will be heard by the U.S. Supreme Court this month. The rate of false conviction in regular criminal cases means that there will be a much higher rate of false detention in these “enemy combatant” cases, since these people are detained without any of the safeguards that adhere in the criminal process (lawyers, cross-examination).