False confessions in criminal cases are very hard to reverse in the minds of police, jurors and judges, even when substantial evidence is available to show that the confession is false.
Saul Kassin of the John Jay College of Justice has a fascinating paper in American Psychologist [abstract free, $ for full article] on false confessions, in which he presents some startling findings on why innocent people confess.
Police often bluff to suspects that they have airtight evidence and the confession is just a formality to confirm what they can already prove. Kassin and his colleagues tried this same technique in experiments in which subjects who were typing were told that they had hit the wrong key and crashed a computer’s hard drive. When told that all keystrokes were recorded for later review, innocent subjects became more likely to confess to having hit the wrong key.
Apparently, innocent experimental subjects assumed there was no harm in falsely confessing as they would be exonerated by the airtight evidence later. In an actual criminal case, this same assumption by an innocent suspect can lead to a wrongful conviction when the police are only bluffing about the existence of the airtight evidence.