Mark Kleiman asks a good question:
Having worked on the problems of crime control for almost thirty years, I tend to be much more sympathetic to the viewpoints and operational needs of law enforcement agencies than the average of the people I usually agree with politically. But on one point, I find myself utterly unable to understand what my friends in the law enforcement biz could possibly be thinking: why isn't it as obvious to them as it is to me that clearing innocent people is just as important a goal of law enforcement as nailing guilty ones?
I agree 100% that this should be a coequal goal with convicting the guilty; but it doesn't surprise me that it isn't. Human beings are such irrepressible optimists, so naturally aversive to meditating upon their own failures, that psychologists have a technical term for the rare people who are predisposed to clearly and accurately assess their achievements: "depressives". When we fail, the natural urge is to cover it up--to others, in order to preserve our status, and to ourselves, in order to preserve our peace of mind. Undoubtedly, the folks at the FBI who decided not to notify people that they'd been convicted on faulty evidence reasoned that those people were all probably guilty anyway, and no real harm had been done, so why rock the boat?
The more important question, I think, is why the rest of us don't spend more time worrying about false convinctions. What I've read about the Jeffrey MacDonald case, for example, makes it clear that at the very least, prosecutorial misconduct and dubious forensic testimony played some role in his conviction. This should bother us whether or not he's guilty, since presumably the kind of games the prosecutors played with the evidence have been inflicted on other, less notorious, defendants who may have been innocent. Yet there's been little interest from any quarter.