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Saturday, May 08, 2010

The Unreliability of Eyewitness Testimony: A Case Study

Eyewitness testimony is notoriously unreliable. This has been shown empirically on a number of occasions. In my introspection class last semester we decided to test this claim in a class experiment.

The class was attended by a real lawyer Tom, who was professionally trained to query eyewitnesses. Chris was assigned the role of police officer, Alex was assigned the role of juror, and Lisa, Jessica and Matt were assigned the roles of criminals and victims.

Tom, Chris and Alex were asked to leave the room. Lisa, Jessica and Matt were then told to go to the main office and plan a crime. They were also told to change their clothes and enter the room later wearing accessories, as they saw fit.

I then instructed the rest of the class to pretend that they were at a cafe. They were told to engage in real conversations with each other, as they would at a real cafe. They were furthermore asked not to pay any special pay attention to Lisa, Matt and Jessica, were they to enter the room, unless there was something special to pay attention to.

Jessica and Matt then entered the room, sat down, and I overheard them engage in a conversation about cats. Then Lisa entered the room, noticed Jessica and Matt and got terribly upset. An argument took place, and Lisa then stabbed Matt and ran away. One of the cafe patrons called the police on his cell phone. Chris then came and questioned Jessica and Matt (who survived the stabbing). He caught Lisa and then questioned her too.

Tom (the lawyer) interviewed victims, criminals, the police officer, and eyewitnesses. Then the trial began. Tom called and queried people, as he saw fit, one at a time. Finally Alex the juror was asked to decide which of the eyewitnesses was the most reliable.

Alex said that he thought Kristina was the most reliable eyewitness. Her report was clear and to the point. She also offered many details which were lacking in the other eye-witnesses' accounts. She looked self-confident and reliable and used very few modifiers of the sort "I believe", "I think", "probably", "could be", "might have".

As it turned out, Kristina was the least reliable eyewitness. She got the color of Lisa's shirt wrong, and there were various other inaccuracies in her story. Our class experiment had confirmed the existing theory: Eyewitness testimony is notoriously unreliable. What's more: We are unable to tell when it is.

All the eyewitnesses wrongly categorized the crime as a jealousy stabbing which involved a man (Matt), his new lover (Jessica) and his old lover (Lisa). In fact, Jessica and Lisa were lovers, and Jessica was cheating on Lisa!

2 comments:

Anonymous said...

HI, Jonathan Speke Laudly here,

The author of the Perry Mason novels, Earl Gardner, was himself a lawyer.
He once gained aquittal for a chinese man after a sworn witness
identified the chinese man sitting next to Gardner at the defender's table as the culprit.
Gardner at once called into the courtroom the real defendant, who had been waiting in the hallway. Gardner had replaced him with another chinese man.
Yes, eyewitness accounts are notoriously fallable.
What is amazing and disgusting to me is the cocksure arrogance shown by prosecutors, judges and jurors in the face of such general unreliability, when they have convicted a defendant based upon such information. God protect me from such people!

Brit Brogaard said...

Right, one of my students, who was a juror recently, told me that the suspect was convicted on the basis of eyewitness reports alone! No weapon had been found, no fingerprints, etc. Apparently one of the eyewitnesses had been watching television. It was about someone who had been convicted for a different offense. Then she had an AHA moment and went to the police. There she identified the suspect from a line-up. But did she remember him from the crime scene or from television?