The reliability of witness testimony is a vastly complex subject, but legal scholars and forensic psychologists say it’s possible to extract the truth from contradictory accounts and evolving memories. According to Barbara Tversky, professor emerita of psychology at Stanford University, the bottom line is this: “All other things equal, earlier recountings are more likely to be accurate than later ones. The longer the delay, the more likely that subsequent information will get confused with the target memory.”
Memory is a reconstructive process, says Richard Wise, a forensic psychologist at the University of North Dakota. “When an eyewitness recalls a crime, he or she must reconstruct his or her memory of the crime.” This, he says, is an unconscious process. To reconstruct a memory, the eyewitness draws upon several sources of information, only one being his or her actual recollection.
“To fill in gaps in memory, the eyewitness relies upon his or her expectation, attitudes, prejudices, bias, and prior knowledge. Furthermore, information supplied to an eyewitness after a crime (i.e., post-event information) by the police, prosecutor, other eyewitnesses, media, etc., can alter an eyewitness’s memory of the crime,” Wise said in an email.
That external input is what makes eyewitness testimony so unreliable. Eyewitnesses are generally unaware that their memory has been altered by post-event information, and feel convinced they’re recalling only the incident itself. “Once an eyewitness’s memory of the crime has been altered by post-event information, it is difficult or impossible to restore the eyewitness’s original memory of the crime,” Wise told Life’s Little Mysteries.
Posted on June 4, 2012 at 6:36 AM •
How do most wrongful convictions come about?
The primary cause is mistaken identification. Actually, I wouldn’t call it mistaken identification; I’d call it misidentification, because you often find that there was some sort of misconduct by the police. In a lot of cases, the victim initially wasn’t so sure. And then the police say, “Oh, no, you got the right guy. In fact, we think he’s done two others that we just couldn’t get him for.” Or: “Yup, that’s who we thought it was all along, great call.”
It’s disturbing that misidentifications still play such a large role in wrongful convictions, given that we’ve known about the fallibility of eyewitness testimony for over a century.
In terms of empirical studies, that’s right. And 30 or 40 years ago, the Supreme Court acknowledged that eyewitness identification is problematic and can lead to wrongful convictions. The trouble is, it instructed lower courts to determine the validity of eyewitness testimony based on a lot of factors that are irrelevant, like the certainty of the witness. But the certainty you express [in court] a year and half later has nothing to do with how certain you felt two days after the event when you picked the photograph out of the array or picked the guy out of the lineup. You become more certain over time; that’s just the way the mind works. With the passage of time, your story becomes your reality. You get wedded to your own version.
And the police participate in this. They show the victim the same picture again and again to prepare her for the trial. So at a certain point you’re no longer remembering the event; you’re just remembering this picture that you keep seeing.
Posted on August 30, 2010 at 12:05 PM •
Witnesses are much more accurate at identifying criminals when computers assist in the identification process, not police officers.
A major cause of miscarriages of justice could be avoided if computers, rather than detectives, guided witnesses through the identification of suspects. That’s according to Brent Daugherty at the University of North Carolina in Charlotte and colleagues, who say that too often officers influence witnesses’ choices.
The problem was highlighted in 2003 when the Innocence Project in New York analysed the case histories of 130 wrongly imprisoned people later freed by DNA evidence. Mistaken eyewitness identification was a factor in 77 per cent of the cases examined.
Makes sense to me.
Posted on October 7, 2009 at 7:12 AM •
People confess to crimes they don’t commit. They do it a lot. What’s interesting about this research is that confessions—whether false or true—corrupt other eyewitnesses:
A confession is potent evidence, persuasive to judges and juries. Is it possible that a confession can also affect other evidence? The present study tested the hypothesis that a confession will alter eyewitnesses’ identification decisions. Two days after witnessing a staged theft and making an identification decision from a lineup that did not include the thief, participants were told that certain lineup members had confessed or denied guilt during a subsequent interrogation. Among those participants who had made a selection but were told that another lineup member confessed, 61% changed their identifications. Among those participants who had not made an identification, 50% went on to select the confessor when his identity was known. These findings challenge the presumption in law that different forms of evidence are independent and suggest an important overlooked mechanism by which innocent confessors are wrongfully convicted: Potentially exculpatory evidence is corrupted by a confession itself.
When asked to explain their change, subjects revealed they were actually convinced by the confessor, and not simply complying with it, saying, “His face now looks more familiar than the one I chose before.”
Posted on February 4, 2009 at 6:35 AM •
According to this article, “Mistaken eyewitness identification is the leading cause of wrongful convictions.” Given what I’ve been reading recently about memory and the brain, this does not surprise me at all.
New Mexico is currently debating a bill reforming eyewitness identification procedures:
Under the proposed regulations, an eyewitness must provide a written description before a lineup takes place; there must be at least six individuals in a live lineup and 10 photos in a photographic line-up; and the members of the lineup must be shown sequentially rather than simultaneously.
The bill would also restrict the amount of time in which law enforcement could bring a suspect by for a physical identification by a victim or witness to within one hour after the crime was reported. Anything beyond one hour would require a lineup with multiple photos or people.
I don’t have access to any of the psychological or criminology studies that back these reforms up, but the bill is being supported by the right sorts of people.
Posted on February 7, 2007 at 6:38 AM •
Sidebar photo of Bruce Schneier by Joe MacInnis.