Another problem with eyewitness testimony was highlighted with a recent study that showed police officers are more forgetful after a chase or an altercation. A CNN story about the study says that the officers had a briefing on three armed robberies and then shown six photographs of suspects. Then:

The group was split into pairs where one officer rigorously assaulted a punching bag until he was visibly tired, the other did not. They were then taken to a trailer set up to represent a realistic “home” environment complete with a “target” individual who had access to multiple weapons strategically placed around the room.

Each officer went through a scenario where there was a brief but angry verbal confrontation with that person. Shortly after the scenario was over, officers were given three memory tests. They were asked to recall details of their initial briefing, the encounter – and then shown the lineup photographs.

Researchers found the group that physically exerted themselves remembered less information from the original briefing and the encounter with the target individual. In fact, more than 90% of the officers in the non-exertion group could recall at least one detail about the target. Barely a third of the officers who were involved in the physical activity remembered seeing the target person at all.

Although the study was conducted on just police officers, there is no reason to believe that the results would have been any different if they had been conducted on the general public. The participants in the study were screened to ensure that they were physically fit, and, as police officers, they are regularly asked to remember crucial details, often after physical exertion. Only a third of trained officers were able to remember any details at all about the person they encountered, so laypeople are going to have a more difficult time. Winded witnesses simply cannot be trusted to adequately identify suspects. And yet juries continue to give undue credibility on eyewitness identification.