In 1996, the U.S. Department of Justice released a report on the first 28 known cases of DNA exoneration. After studying those and 12 subsequent cases, Mr. Wells discovered that mistaken eyewitness testimony had played a part in about 90 percent of the convictions. Concerned about the high rate of eyewitness error in the DNA cases, U.S. Attorney General Janet Reno invited him to a meeting in early 1997. The guide, published in October, gave scholars the opportunity to show that human memory is not a highly reliable tool for determining guilt in the courtroom. For example, contrary to popular belief, people under stress remember events no better than, and often less well than, they do under ordinary circumstances.
Witnesses also perceive time as moving more slowly during traumatic events.
That, in turn, leads them to overestimate how much time they had to notice details, a key factor of their credibility in court. Researchers cannot ethically recreate the trauma of real crimes. But plenty of field research suggests that witnesses are apt to misidentify people. In addition, all sorts of factors inhibit our ability to recognize and recall facial detail. For instance, psychologists have established that most of us have more difficulty recognizing people of a different race.