The Innocence Project has used DNA technology to overturn hundreds of wrongful convictions. Slate has an excellent two part series on the two main reasons why these people were falsely jailed: eyewitness misidentifications and false confessions.
The series is by law professor Brandon Garrett who has analysed the first overturned 250 cases to examine the psychology behind distorted justice.
This is from the piece onthe biases that in line-ups that have sent people down for long-stretches after being falsely identified:
Where did this false certainty come from? The trial records I looked at suggest that unsound and suggestive police identification procedures played a large and troubling role. Police used unnecessary show-ups, where they presented the eyewitness with just the defendant. Or stacked lineups to make the defendant stand out.
Or offered suggestive remarks, telling the eyewitness whom to identify or to expect a suspect in a lineup. Or confirmed the witness’s choice as the right one. Even well-intended, encouraging remarks, like “good job, you picked the guy,” can have a dramatic effect on eyewitness memory, as psychologists have shown.
Indeed, more than one-third of the cases I looked at involved multiple eyewitnesses, as many as three or four or five eyewitnesses who all somehow misidentified the same innocent person. Further, almost half of the eyewitness identifications were cross-racial. Psychologists have long shown how eyewitnesses have greater difficulty identifying persons of another race.
Both pieces tackles how biases have warped specific high profile cases, sometimes leading to decades of false imprisonment.
Link to Slate piece on eyewitness misidentifications (via @psyDoctor8)
Link to Slate piece on false confessions.
Mind Hacks 
It is curious that so much collective attention and effort is given to the “false negative” side of the innocence/guilt issue, and so little to the suddenly unresolved case that gave rise to the conviction. Both prosecution and defense should (and, I believe, usually do) have an interest in the integrity of the investigation and prosecution of crimes. I wonder how the police officers and prosecutors react when they are shown that the real perpetrator of the crime is still out there.