The Trouble with Eyewitness Testimony

by Sandra Parshall

Why do we continue to give so much weight to eyewitness testimony?

Again and again in the past few years, we’ve seen wrongly convicted people – usually men, usually serving time for rape or murder – freed by DNA evidence after losing years or decades of their lives because a jury believed an eyewitness’s testimony. In some cases, victims and even prosecutors have continued to insist that these people are guilty. They were seen committing the crimes. They must be guilty. 


 
The truth is that the human brain is lousy at remembering details, especially in emotionally charged events. Witnesses and victims remember the emotions far more clearly than they recall the perpetrator’s appearance. As time goes on, the brain alters memories in subtle ways, making them even less unreliable.

The fallibility of eyewitness accounts has been demonstrated in numerous controlled scientific studies and proved in the real world by DNA tests. Police and prosecutors know that five witnesses to the same crime may give five contradictory descriptions of the perpetrator. Yet eyewitness accounts remain the most common “evidence” used to convict people. Despite the popularity of forensics, nothing is more compelling to a jury than a seemingly credible witness on the stand during a trial, pointing at the defendant and declaring, “It was him. He’s the one who did it.” Sometimes, though, it wasn’t him, and he didn’t do it. Sometimes the guilty person goes free while someone who’s innocent goes to prison.

A lot has been written on this subject, with little effect. The latest book about our flawed criminal justice process is In Doubt (Harvard University Press), by Dan Simon, a professor of law and psychology at the University of Southern California. He says that if you use only exonerations in capital murder cases as an indicator, the false conviction rate is around five percent, but he believes that’s a mere fraction of the number of wrongful imprisonments.
 
Simon uses research into the workings of the human brain to prove his conclusions about the destructive use of eyewitness testimony when the future of a human being is at stake. Studies have shown, for example, that our memories are highly selective in what they notice and retain and are not good at registering details of strangers’ faces. In a criminal case, witnesses may unconsciously alter their memories to conform to what they believe the police and prosecutors want – or to fit their own personal bias. Yet even when their recollections change over time, witnesses usually remain convinced that they have an accurate mental picture of what and who they saw.
Simon proposes that all interviews with witnesses, victims, and suspects be recorded and that jurors receive instruction from judges on the possibility that bias may affect testimony. Since prosecutors rely heavily on eyewitness  testimony, they’re not likely to welcome such a warning from the bench.
 
Personally, I’ve read too many stories of innocent people spending half their lives in prison to ever trust eyewitness testimony. If I were on a jury and the only “evidence” presented came from a so-called eyewitness, I would probably not vote to convict because I would still have that all-important shadow of a doubt in my mind.

What about you? Could you send someone to prison for ten, twenty years, for life, on the strength of a witness’s declaration that “It was him. He’s the one who did it”?