How to make eyewitness evidence more reliable

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Eyewitness testimony is one of the most powerful forms of evidence in a trial. It’s also one of the most problematic; in fact, it’s “the number one cause of wrongful convictions,” says Daniel Medwed.

Medwed is a law professor at Northeastern and a member of the new Standing Committee on Eyewitness Identification, which was recently convened by the Massachusetts Supreme Judicial Court. The committee is charged with devising police and court procedures that take into account the central lesson of research on eyewitness testimony: “Our memories of what we see aren’t static. They’re elastic and malleable and change over time,” Medwed says.

The committee, which developed out of a 2013 review of eyewitness evidence by the Supreme Judicial Court, includes judges, prosecutors, police officers, and a public defender, as well as law professors. It met for the first time in mid-February and is just beginning the process of developing recommendations. Medwed said in an e-mail that it’s “too early to guess about the results” of the process, but in an interview, he sketched some of the reforms he said he could imagine the committee considering:

■ Expand the use of double-blind lineups. In this kind of lineup, the administering officer doesn’t know if there’s a suspect included at all, and this fact is communicated to the eyewitness. Double-blind lineups are already in use in Suffolk County; Medwed would like to see them used throughout Massachusetts. He says the technique compensates for the “natural tendency of a witness to pick somebody,” even when they’re not sure, and removes the possibility that the administering officer is providing “subtle cues” about who to pick.

■ Replace simultaneous lineups with sequential ones. In the first kind, the eyewitness looks at all potential suspects at once; in the second, the eyewitness considers potential suspects one at a time. Medwed says research shows that with simultaneous lineups, eyewitness often engage in a comparative process “instead of making an absolute thumbs up, thumbs down assessment,” and that sequential lineups would minimize the risk of wrongful identification.

■ Ask for confidence statements. Eyewitnesses often grow more confident about their statements over time, regardless of whether they’re actually accurate. One way to take this into account is to require eyewitnesses to make “confidence statements” at the time of identification, in which they state how certain they are that the person they’ve identified is the perpetrator.

■ Give juries better instructions. Prior to deliberations, juries could be instructed about how to evaluate the reliability of eyewitness testimony. Instructions could emphasize different research findings depending on the case’s circumstances, like the fact that eyewitnesses are more likely to misidentify a person whose race is different than their own.

Medwed acknowledged that law enforcement officials and defense attorneys often want different things out of criminal justice reforms. In the case of improving eyewitness identification procedures, though, he thinks there’s a lot of common ground. “The idea of accuracy, and getting it right, is a shared value,” he says. “It’s protecting the innocent, and it’s a way of making sure the guilty are somehow accountable.”