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EYEWITNESS misidentification is the number one cause of wrongful convictions in criminal prosecutions. It has played a role in more than 75 percent of the cases of prisoners who have been exonerated by DNA evidence, according to the New York-based Innocence Project, a nonprofit organization dedicated to exonerating the wrongfully convicted.

A new study shows that knowledge of confessions can exacerbate the problem by exerting a corrupting influence on eyewitness memories.

The study, by postdoctoral scholar Lisa E. Hasel of Iowa State University and Saul M. Kassin, of John Jay College of Criminal Justice in New York, found that 61 percent of eyewitnesses who selected a suspect in a lineup changed their pick when they heard that another individual confessed. And of witnesses who could not select a suspect initially, 50 percent changed their minds when they heard about a confession.

A total of 233 prisoners have been exonerated by DNA evidence, according to the Innocence Project. False confessions, guilty pleas, or incriminating statements were present in about 25 percent of these cases.

Hasel told Security Management that the study was prompted in part by a case in which a man was coerced into confessing to a rape and murder he could not have committed. Although there were several witnesses who stated that they had seen the accused at a birthday party at the time the crime occurred, many of those witnesses changed their stories after hearing about the confession.

In court, the confession and eyewitness stories would typically be viewed by juries as two separate, strong pieces of evidence, but, in this case, “they really should just be considered one piece of evidence, because the eyewitness would not have existed had the confession not been given,” Hasel says.

The law enforcement and legal communities need to understand that confessions and witness identifications are often not independently collected, she says. Ideally, once that is understood, the authorities will attempt to control against it, says Hasel.

Many experts with experience in eyewitness identification are not surprised by Hasel and Kassin’s findings. “Evidentiary independence is fiction,” says Robert Shomer, who has testified as an eyewitness expert in more than a thousand trials. “In fact, it’s only one example of completely outmoded models of human behavior that the legal system uses,” says Shomer.

The way the legal system approaches eyewitnesses is contrary to scientific research on how memory works, Shomer adds. He says the legal system acts as if people are like cameras, taking pictures of people, storing them in compartments, and pulling that data out when it is needed for identification. But that’s not how the mind works, Shomer says. Memories fade and can be influenced by external factors, as Hasel and Kassin point out.

What can be done to prevent eyewitness identification corruption in the future? Various bodies, including the U.S. Department of Justice (DOJ), have published recommendations on how to improve police lineups. For example, one of the universal recommendations is that a lineup administrator be “blind” (not told who the suspect is) so that he or she cannot influence the witness.

Investigators speaking with an eyewitness should not tell the witnesses about any confession, says Nancy Steblay, a psychology professor at Augsburg College in Minneapolis and an eyewitness identification scholar. Ideally, the investigator should not know about the confession either.

Keeping eyewitnesses from knowing about a confession for the duration of the trial can be tough in our open society “because witnesses will read about things in newspapers and witnesses will have conversations with detectives,” says Steblay.

“What’s very important,” she says, “is at the time of that lineup procedure, and at the time the detective is gaining eyewitness evidence…during that brief time span, you have to make sure you collect all the information before there’s any kind of feedback or information given to the witness,” and if you can do that, then perhaps “you get a nice, clean slice of what that witness really can remember.”

Another recommendation for lineups is that they should be sequential, showing the witness one picture or suspect after another, rather than having suspects line up together. The reason for this is that in simultaneous lineups, a witness is comparing the individuals in the lineup to each other and might pick the one who looks most like the perpetrator, even if that individual is not guilty, while in a sequential viewing, the witness must just make an absolute judgment on whether an individual is likely the perpetrator or not.

Although some states, including New Jersey and Wisconsin, have adopted all or a portion of the DOJ recommendations, many police departments in the nation have yet to reform their strategies.

When asked why they do not change, some cite the difficulty in establishing a means by which they can have a detective not know of a suspect when interviewing witnesses, say Steblay and Shomer.

Shomer says that more must be done to evaluate and update standards for evidence gathering so that “when a sheriff or a police officer says to a prosecutor, ‘Well, we have an identification,’ the prosecutor says ‘Well, not according to the rules of evidence that we go by.’”