The Economist asks Radley Balko about the biggest problem with the criminal justice system. Part of his reply:
[T]he incentive problems are most apparent with prosecutors. Prosecutors get no credit for cases they decide not to bring, either because of a lack of evidence or because pressing charges wouldn't be in the interest of justice. They're only rewarded for winning convictions. That's what gets them promoted, or re-elected, or gives them the elevated profile to run for higher office. Every incentive points toward winning convictions. And particularly with prosecutors, there's really no penalty at all for going too far to get a guilty verdict. One real disservice the Duke lacrosse case did for the criminal-justice system is it put in the public consciousness the idea that bad actors like Mike Nifong are regularly disciplined for misconduct. In truth, that case was really exceptional.