The trouble with eyewitness identification, explained

“I saw it with my own eyes.”

There is little more convincing than the confident declaration of a witness, absolutely sure of her own memory. Eyewitness testimony has long enjoyed a lofty status as “the gold standard of the criminal justice system,” the real stuff of proof.  Yet it has also been decisively dethroned by modern science.

While scientists of the mind have long questioned the reliability of eyewitness testimony, it took the public spotlight on Troy Davis earlier this fall to cast more than a reasonable doubt in the minds of many. But how much do we really know about eyewitness identification, and what’s being done about it? Here we sort through the science, the law, and the future plans for this fundamental pillar of the criminal justice system.

What does the science say?

As TIME, the New York Times, and Slate note, there are all sorts of factors that affect how accurately witnesses can identify a suspect: how far they were from the scene, whether it was daytime or nighttime, whether they were under the influence of drugs or alcohol, whether the person they identified was of a different race. After the crime, other factors can skew a person’s memory during the identification process: how much time has elapsed since the crime, suggestions from the police officer, having seen photographs of the prime suspect, or even just wanting to believe a certain story. Over 30 years of peer-reviewed research on eyewitness memory has found that it’s pretty much inherently unreliable.

The problem is, we don’t believe it is. We tend to think that memory, especially our own, is just fine, thank you very much. As reported in Scientific American, 63 percent of US adults think that memory is about as good as a video camera. And according to the American Psychological Association, jurors tend to over believe eyewitness accounts. But the fact is, our memories are far from perfect.

How does this affect the criminal justice system?

In a big way. According to the Innocence Project, eyewitness misidentification is “the single greatest cause of wrongful convictions nationwide.” In 75 percent of cases where a suspect was found innocent because of DNA evidence, it was eyewitness testimony that put them behind bars in the first place. All sorts of problems can crop up, from discrepancies in a person’s description to problems in the line-up procedure.  The Virginia Law Library has a chart showing all the ways eyewitnesses have been mistaken in cases where the suspect was later exonerated.

And it’s not just that innocent people are convicted. As Santa Clara County Assistant District Attorney Karyn Sinunu-Towery tells TIME, “every time there’s a wrong identification, it means the real criminal is still out there.”

What are some easy ways to help fix the current system?

According to Nancy Skeblay, a psychologist at Ausburg College who researches eyewitness accuracy, we could see major improvements by simply switching the way a police lineup is done. Traditionally, witnesses are shown a row of photographs all at once and asked to pick out the culprit. But research suggests that when witnesses are shown each photo one at a time – a “sequential lineup” – they make fewer errors. It’s also important for the lineups to be double-blind, or administered by someone with no knowledge of the case. That way the officer won’t unintentionally sway the witness towards picking a particular suspect.

Finally, merely telling jurors about the well-known problems with eyewitness accounts may dampen their confidence in the testimony. The Innocence Project also has a list of other reforms that could improve the system.

So what’s being done about it?

Sadly, not too much, but that may change. Right now only ten jurisdictions across the US (New York is not one of them) use the recommended double-blind sequential line-up, and most don’t have strict regulations for how eyewitness accounts are handled in court. But this summer, the New Jersey Supreme Court set new guidelines for how its courts assess eyewitness identifications (here’s WNYC’s comprehensive podcast on the subject). New Jersey could serve as a model for other courts looking to make similar changes.

And for the first time in 33 years, the Supreme Court is hearing a major case about the place of eyewitness testimony in the criminal justice system. As this Slate piece makes clear, Perry v. New Hampshire may not be the ideal forum for a landmark decision (the high court looks like it will avoid confronting the issue head on). But given the explosion of commentary on the subject, it seems as though the failure of memory in the courtroom is finally getting the public attention it deserves.