According to U.S. Supreme Court Justice Sonia Sotomayor, evidence from eyewitnesses is “a unique threat to the fairness of trial.” She cited research that found eyewitness misidentifications to be the “single greatest cause” of wrongful convictions in the United States.
Bad eyewitness identifications put innocent people in prison. There are many reasons why they happen, and some of them can be prevented.
In 2016, the U.S. Court of Appeals for the Third Circuit, based in Philadelphia, commissioned a report on the reliability of eyewitness evidence. The results offer a clear picture of one weakness in the criminal justice system.
One major issue is that witnesses are typically nervous about identifications and want to be helpful. Therefore, they often try to deliver the result they think law enforcement is hoping for. Meanwhile, the officers are often hoping for a particular person to be identified and can unintentionally give subtle clues about who that might be.
Running a fair lineup
In a fair lineup, neither the officers involved nor the witness would know whether the suspect is even in the lineup, much less who that suspect might be. This is called a “double blind” setup.
The report also found that eyewitness identifications were less reliable when the witness was shown the same suspect more than once. For example, when a witness is shown a photo in a photo array and then sees the same person in a lineup, they are prone to conclude that that person is the perpetrator.
Composite sketches also introduce error. Some eyewitnesses may look for a suspect to resembles the sketch rather than relying on their memory of the actual perpetrator.
Giving a witness books of mug shots to browse has also been associated with mistaken identifications. At least one jurisdiction, New Jersey, has stopped mugshot searching altogether.
A few strategies can increase the chances of a fair identification. One is to make clear to the witness that the perpetrator might not be in the photo array or lineup. Another is to remind the witness that it’s just as important to free an innocent suspect as it is to identify a guilty one. Both of those warnings have been mandated by some jurisdictions.
The filler participants — people known to be innocent — should match the witness’s original description rather than looking similar to the police’s suspect.
When a witness identifies someone, the administrator should immediately ask the witness to gauge how certain they are of the ID.
Finally, the police should refrain from any commentary, even when the witness’s job seems over. This is meant to prevent police from cementing an unsure witness’s identification.
