Science has prevailed over injustice in the state of New Jersey, where all jurors will soon learn about memory's unreliability and the limits of eyewitness testimony.

According to instructions issued July 19 by New Jersey's Supreme Court, judges must tell jurors that "human memory is not foolproof," and enumerate the many ways in which eyewitness recall can be distorted or mistaken.

Cognitive scientists who study memory have celebrated the new requirements.

"Eyewitness identification evidence is seen by jurors as being trustworthy and reliable," said psychologist Charles Brainerd of Cornell University, who specializes in memory. "The science shows exactly the opposite."

The guidelines were prompted by State v. Henderson, in which the New Jersey Supreme Court overturned the conviction of Larry Henderson, an accused murder accomplice whose identification from a lineup was unduly influenced by police.

Though egregiously unjust, Henderson's case was hardly unusual: Eyewitness misidentification is the most common cause of wrongful conviction in the United States. Of prisoners exonerated by DNA testing, some 75 percent were mistakenly identified.

"In the U.S., in 95 percent of felony cases, there's no evidence other than what people say and report," Brainerd said. "Over the years, we've had thousands of experiments on eyewitness identification. Under the best conditions, people have about a 50/50 chance of getting it right."

Rarely do the best possible conditions prevail. The vast majority of eyewitness identifications are based on police presentations of photographic lineups, which may be constructed so as to point subtly at a lead suspect.

A witness may be shown a suspect's mug shot, for example, while other photographs in an array come from driver's licenses. And while arrays should ideally contain a group of similar-looking people, some may obviously not be suspects.

Sometimes the bias isn't subtle, but blatant. "I had one case in Missouri in which I was given the six-person photo spread used in the case, and there was a checkmark under the suspect," said Brainerd.

Psychologist Gary Wells of Iowa State University, who served as an expert in State v. Henderson, called New Jersey's new rules "a great advance." But he warned that jury instructions aren't always effective.

"There's no substitute for trying to prevent mistaken identifications from occurring in the first place," he said, calling for the development of "even better lineup procedures and safeguards." These can include computer-generated lineup arrays designed to minimize bias.

In stark contrast to New Jersey's example, some states don't allow jurors to hear criticisms of eyewitness fallibility from experts like Brainerd and Wells. Cognitive scientists may also be overruled.

"In the few trials where I testified on eyewitness reliability, the introduction to the jury directed them to place confidence in eyewitnesses," said psychologist Barbara Tversky of Stanford University. "That certainly disturbed me as someone who is all too aware of the fallability and malleabilty of memory."

Another example of reform comes from the United Kingdom, where an especially egregious case of mistaken identification prompted the country to forbid convictions based solely on eyewitness identification. While that won't likely occur anytime soon in the United States, other states may follow New Jersey's lead.

"The developments in New Jersey are thrilling," said cognitive scientist Elizabeth Loftus of the University of California, Irvine. "I've been working with a judge in Pennsylvania to do something similar, and anticipate such efforts will be forthcoming in many states."

Image: James Cridland/Flickr