How (purported) Confessions Taint Other Evidence
Social science confirms what defense lawyers have long known: when an eyewitness thinks a particular individual has confessed to the crime, they are more likely to identify that person as the criminal, and to be more certain about it, than if they did not have information about the confession. People who previously identified nobody will identify the person who confessed once they hear about the confession, and say that they now recognize the perpetrator–they claim that they are not merely relying on the fact of the confession.
The problem is that they are.
Lisa Hasel of Iowa State University and Saul Kassin of the John Jay College of Criminal Justice did a study in which college students witnessed the staged theft of a laptop. They were then shown a lineup of suspects and asked to identify the perpetrator. Two days later, they were given information that somebody in the lineup had confessed. There were a bunch of variations, but here’s the smoking gun:
Among people who had identified somebody in the first lineup, 61% changed their mind when told that a different person had confessed. 100% of those who changed their mind picked the person who allegedly confessed.
Among people who had identified nobody, 50% picked the person who they were told confessed. Again, none changed their minds but picked a non-confessor.
Why is this a problem? Because people confess falsely. How’s this for a scary scenario: an innocent person is arrested and the eywitness says “i’m not sure, I think it might be him.” The police tell the innocent person that the jig is up, the eyewitness IDd them. They tell the innocent person that things will go easier for them if they confess. So they sign the confession that the police have already written out for them. Then the police go back and tell the eyewitness that they got a confession. Now the eyewitness is prepared to go to court and testify to the identification with complete certainty. Any doubt has been erased by the confession.
It’s not just eyewitnesses, either. Hasel and Kassin cite a 2006 study in which 17% of fingerprint experts change their previous (correct) conclusions when told (falsely) that the suspect had confessed (suggesting that the prints should match) or that the suspect was locked up at the time of the offense (suggesting that the prints should not match).
The take-home message from these results: attorneys and courts should be suspicious of all evidence in cases with confessions–not just the confession itself.
You can read the full article at
http://www.psychologicalscience.org/journals/ps/20_1_inpress/Hasel.pdf
Posted by AndyCowan on December 23rd, 2008 :: Filed under In the News
Tags :: confessions, forensic evidence, identifications, social science and law