Witness for the Prosecution

When aviator Charles Lindbergh’s baby son was kidnapped from his crib and later found murdered in the spring of 1932, the nation was transfixed by the crime and the two years of police work that followed. Bruno Hauptmann, a German carpenter, was eventually arrested, tried, convicted and executed for the crime. He never confessed. But more than 200 other people did.

What is it with false confession? It seems crazy on the face of it, to take the blame for a crime you didn’t commit. And indeed experts believe that many false confessors—including those in the Lindbergh case—are mentally disturbed attention seekers. Others are taking the fall for someone else, while still others may have been illegally coerced into confessing. According to one estimate, fully a quarter of convictions later overturned by DNA evidence involved a false confession.

Confessions are powerful evidence in court. But in our legal system, confessions are supposed to be just one more piece of evidence, weighed along with fingerprints and alibis and eyewitness testimony and so forth. But is this possible? Are judges and juries capable of weighing evidence fairly when they’re faced with someone proclaiming: I did it? Indeed, are eyewitnesses themselves immune to the persuasiveness of a confession? Or is a confession so potent that it trumps everything else?

Legal experts are obviously very interested in this question, and psychologists have been working to piece together an answer. In a recent study, Lisa Hasel of Iowa State University and Saul Kassin of John Jay College actually created a crime scene to explore the mind of the eyewitness and the integrity of eyewitness testimony. Put yourself in the position of a witness:

You are one of several people sitting in a university laboratory, waiting to participate in a study. At some point, a white man walks in, picks up a laptop from the desk, and leaves. You don’t think anything of it, but a few minutes later, a woman enters the room and announces, with obvious distress, that her laptop is missing. It’s been stolen, and you’re the eyewitness. The police recruit you to help solve the crime.

The first thing you do is look at a line-up of white men, to see if you can identify the thief. Once you’ve fingered the thief (or not), you go home, but you’re summoned back a couple days later. The crime is still unsolved, although all the men in the lineup have by this time been interrogated. You learn that the person you identified as the thief has in fact confessed. Case closed.

But wait. What if you learn instead that one of the other men has confessed? Or that they are all swearing up and down that they are innocent? And what if you had fingered nobody on the day of the crime, and you learn now that one of the men has confessed?

These are all among the scenarios that Hasel and Kassin created for volunteers in their experiment. They wanted to see if eyewitnesses would be swayed enough by a confession to change their mind about their memory of the crime. Would they retract their original statement, fingering the confessor? Or stick to their guns?

The results, reported in the January issue of the journal Psychological Science, are a bit unsettling. None of the men in the lineup was in fact the real thief, so the only reliable testimony came from those who fingered no one. That is, the vast majority did identify an innocent man as the criminal, and many with confidence. That’s disturbing in itself, but it gets worse. While few were persuaded by claims of innocence—that happens all the time—a disturbing number changed their mind when a suspect confessed. An astonishing 60 percent who had fingered one suspect flip-flopped when a different man confessed. Even those who had been very sure of their original identification experienced a steep drop in confidence. When asked to explain their change of heart, most said they had been mistaken earlier, that their memories had fooled them.

How about the rare ones who (correctly) refused to finger any one of the original six in the lineup? These witnesses would seem to be especially cautious about falsely accusing someone of a crime. Yet fully half of these eyewitnesses also changed their minds when told that a specific suspect had confessed. That particular suspect’s face was now familiar to them as the face of the criminal, where it had not been before.

Remember that these were all false confessions. The guy who actually walked off with the laptop was never seen again. Mock jury studies have shown that jurors will ignore all sorts of exculpatory evidence if it does not fit with what they believe. This study suggests that false confessions can corrupt criminal evidence before the jury ever gets to weigh it at trial.

For more insights into human nature, visit “We’re Only Human” at www.psychologicalscience.org/onlyhuman. Excerpts from the blog also appear regularly in the magazine Scientific American Mind and at www.sciam.com.