For years I thought this was a trivial issue. The real problem with American justice was our zeal to over-punish the guilty (especially those guilty of largely preventive crimes). Errors must occasionally happen in every system, but given the growing budgets and training of police, such errors must be decreasing, right?
Wrong. Now I believe wrongful conviction is a robust and persistent feature of contemporary law enforcement. Check out two stories in Sunday's New York Times that describe very typical patterns seen in such cases (Brenda Goodman on the Troy Davis case; Peter Applebome on Richard LaPointe's case -requires Times Select-).
I believe that wrongful convictions may be going up despite better training of police and more legal representation for defendants than was true in the past. Rather than being aberrational, such events are highly predictable and driven by several features of governing through crime:
1. Once crime was upgraded to a "war," it was inevitable that rule-based limitations on police would be internally undermined. If you are in a war against a criminal class then it does not matter whether you get them for trivial crimes or serious ones, whether the evidence is persuasive or whether it has to be doctored. If the way to reduce crime is to mass incarcerate this "criminal class," questions of guilt are inevitably technicalities.
2. Mass criminalization of social problems like mental illness, homelessness, and poverty, means that most jails and many poor neighborhoods are packed with people who can be pressured into giving false testimony in order to avoid lengthy jail sentences. Because so many of these crimes are prosecuted on a racially selective basis, if you are Black or Hispanic, the odds that somebody in jail (or rounded up the street) will know your name are much higher than for whites.
3. In an age of governing through crime, police and prosecutors face much more pressure to "solve" violent crimes, especially when they happen to victims who, because of age, race, or social standing, become magnets for the media.
For a fuller analysis, check out the following online "work in progress":
Jonathan S. Simon (April 26, 2007) Recovering the Craft of Policing: Wrongful Convictions, the War on Crime, and the Problem of Security