False Confessions May Lead to More Errors in Evidence, a Study Shows

A man with a low IQ confesses to a gruesome crime. Confession in hand, the police send his blood to a lab to confirm that his blood type matches the semen found at the scene. It does not. The forensic examiner testifies later that one blood type can change to another with disintegration. This is untrue. The newspaper reports the story, including the time the man says the murder took place. Two witnesses tell the police they saw the woman alive after that. The police send them home, saying they “must have seen a ghost.” After 16 years in prison, the falsely convicted man is exonerated by DNA evidence.

How could this happen? “False confessions can corrupt other evidence, both from laypeople and forensic experts,” says John Jay College of Criminal Justice psychologist Saul Kassin, summarizing a new study conducted with Daniel Bogart of the University of California Irvine and Nova Southeastern University’s Jacqueline Kerner. The findings, which will appear in an upcoming issue of Psychological Science, a journal published by the Association for Psychological Science, have far-reaching implications for judges and juries, prosecutors and defense attorneys.

Confessions, when true, are an important tool in convicting criminals. But false confessions frequently play a major role in convicting innocent people. Experiments show that juries and potential witnesses are influenced by confessions even if they know they were coerced. Also in the lab, experienced polygraph examiners, fingerprint experts, and other experts, when informed of a confession, see what they expect to see—that is, evidence of guilt.

To back up these findings with real-life data, the psychologists thoroughly reviewed the trial records of 241 people exonerated by the Innocence Project since 1992. Of these, 59—or 25 percent—involved false confessions, either by the defendant or an alleged accomplice. One-hundred eighty—or 75 percent—involved eyewitness mistakes. The analysis revealed that multiple errors turned up far more often in false confession cases than in eyewitness cases: 69 percent versus fewer than half. And two thirds of the time, the confession came first, followed by other errors, namely invalid forensic science and government informants.

Kassin believes the findings “greatly underestimate the problem” because of what never shows up in court: evidence of innocence. Told the suspect confessed, “alibi witnesses back out, thinking they’re mistaken,” police stop searching for the real culprit. “We show that confessions bring in other incriminating evidence that is false. What we don’t see is a tendency to suppress exculpatory evidence.”

The study throws doubt on a critical legal concept designed to safeguard the innocent: corroboration. Appeals courts uphold a conviction even if a false confession is discovered, as long as other evidence—say, forensics or other witness testimony—independently shows guilt. “What these findings suggest is that there may well be the appearance of corroboration,” says Kassin, “but it is false evidence that was corrupted by the confession—not independent at all.”

Already, many states require that interrogations be taped, so that confessions are not coerced or taken when the suspect is in psychological distress. With this study, “Juries and judges have more reason to critically evaluate the conditions under which that other evidence was taken, too.”[1]

Radiolab: Do I know you?

How do you know your mother is really your mother? It's simple, right? You look at her, you recognize her, enough said. Well, in this podcast...it may not be that simple.

It turns out that recognizing people, even the people we know the best, is more about how they make us feel than what we see in front of our eyes. And when your feelings about someone get jumbled, it can be disorienting, even traumatic. In this the podcast we talk to Dr. Carol Berman and Dr. V.S. Ramachandran to explore the psychology and neurology behind a rare but disturbing delusional disorder called Capgras.[1]

In the classic 1956 film Invasion of the Body Snatchers, the residents of a fictional town in California are beset by the feeling that their friends and family have been replaced by impostors. In the movie, this apparent delusion is not delusional at all: The townspeople are in fact being replaced — by aliens, no less.

Numerous sci-fi films since have capitalized on our fear of being surrounded by duplicates — replicas who look just like our loved ones but are not. And while there have so far been no confirmed cases of a human being replaced by an alien or any other life-form, the feeling that your loved one has been replaced by someone else can be very real.

Consider these two true stories:

A 37-year-old woman came into the office of Carol Berman, a psychiatrist at New York University Medical Center, with a strange complaint. She had returned to her house recently to find a man sitting on her couch. He was familiar, sort of, and he was wearing her husband's clothes. But something didn't feel right to this woman. She felt a strange kind of emptiness when she looked at him. She was struck by the very deep sense that her husband had somehow been replaced by this strange man.

A student at the University of California, San Diego was severely injured in a car accident. After several weeks in a coma, he regained consciousness and seemed to be doing fine. But according to V.S. Ramachandran, a neuroscientist at the university, when the patient's mother came to see him, he exclaimed, "Who is this woman? She looks just like my mother, but she's an impostor! She's some other woman pretending to be my mother."

Rare Delusional Disorder

Both patients, it turns out, were suffering from a rare delusional disorder, called Capgras. Capgras delusion can be brought about by a variety of conditions — changes in brain chemistry associated with different mental illnesses, or physical trauma to the brain — but the delusion always involves the distinct feeling that the people around you have been replaced by impostors. While they may look and act just like the real person, some essence of the person is missing, almost as though "the soul of the person isn't in there," Berman says.

Ramachandran thinks that Capgras can be better explained by a structural problem in the brain. According to Ramachandran, when we see someone we know, a part of our brain called the fusiform gyrus identifies the face: "That looks like mom!" That message is then sent to the amygdala, the part of our brains that activates the emotions we associate with that person. In patients experiencing Capgras, Ramachandran says, the connection between visual recognition and emotional recognition is severed. Thus the patient is left with a convincing face — "That looks like mom!" — but none of the accompanying feelings about his mother.Currently, no one is certain of the underlying cause of Capgras, and there are different ways of explaining what is happening to these people. According to Berman, Capgras might be caused by psychological dissonance. There are usually things about the people close to us that we don't like. Normally, we combine these things with the parts we do like and develop a general emotional response to the whole person. But in some extreme cases, a change in character or a newly noticed behavior can just be too difficult to accept, to integrate into the whole. And so, rather than reframing our sense of who that person is, our brain just says: "That must not really be him."

That's Not My Mother

Ramachandran holds that we are so dependent on our emotional reactions to the world around us, that the emotional feeling "that's not my mother" wins out over the visual perception that it is. The compromise worked out by the brain is that your mother was somehow replaced, and this impostor is part of a malevolent scheme.

Ramachandran thinks there's good evidence for this explanation of Capgras, in part because of an odd quirk in his patient's behavior. When his mother calls him on the phone and he hears her voice, he instantly recognizes her. Yet if she walks in the room after that call, he is again convinced that she is an impostor.

Why? Ramachandran says that our visual system and auditory system have different connections to the amygdala, so while the auditory recognition triggers an emotional response in his patient, visual recognition does not.

Treating The Illness

Capgras is very rare, and little is known about how to treat it. Those who have been afflicted with Capgras due to physical brain trauma may eventually re-establish the connection between perception and emotion. (Ramachandran's patient, for example, eventually recovered from his delusion.) And patients who experience Capgras alongside other mental disorders may be helped by medication. But for many Capgras patients, there is no treatment, and no amount of talk or reasoning can cure them.

While the feeling that the people around you have been replaced by impostors is certainly terrifying to imagine, the effect on the supposed impostor can be devastating, too. Carol Berman's husband began suffering Capgras after the onset of a particular kind of dementia in which neural transmission between different parts of the brain decays. Some days he knows that Berman is his wife. But other days, the woman who walks through the door is an impostor.

"I hope he's recognizing me," says Berman, "but you never know what you're going to get when you get back home."[2]

Radio Lab: Memory and Forgetting

What is self in a world where your memories can be deleted?

This hour of Radiolab, a look behind the curtain of how memories are made...and forgetten.


Remembering is an unstable and profoundly unreliable process--it’s easy come, easy go as we learn how true memories can be obliterated, and false ones added. And Oliver Sacks joins us to tell the story of an amnesiac whose love for his wife and music transcend his 7-second memory.[1]