Science tells us not to rely on eyewitnesses

Posted on October 18, 2016

Photo: flickr

Eyewitness identification typically involves selecting the alleged perpetrator from a police lineup, but it can also be based on police sketches and other methods. Soon after selecting a suspect, eyewitnesses are asked to make a formal statement confirming the ID and to try to recall any other details about events surrounding the crime. At the trial, which may be years later, eyewitnesses usually testify in court.

Surveys show that most jurors place heavy weight on eyewitness testimony when deciding whether a suspect is guilty. But although eyewitness reports are sometimes accurate, jurors should not accept them uncritically because of the many factors that can bias such reports. For example, jurors tend to give more weight to the testimony of eyewitnesses who report that they are very sure about their identifications even though most studies indicate that highly confident eyewitnesses are generally only slightly more accurate - and sometimes no more so - than those who are less confident.

How could so many eyewitnesses be wrong? The answer lies in studying memories, or more specifically, memory reconstruction. Psychologists have found that memories are reconstructed rather than played back each time we recall them. The act of remembering, says eminent memory researcher and psychologist Elizabeth F. Loftus of the University of California, Irvine, is "more akin to putting puzzle pieces together than retrieving a video recording." Even questioning by a lawyer can alter the witness's testimony because fragments of the memory may unknowingly be combined with information provided by the questioner, leading to inaccurate recall.

Many researchers have created false memories in normal individuals; what is more, many of these subjects are certain that the memories are real. In one well-known study, Loftus and her colleague Jacqueline Pickrell gave subjects written accounts of four events, three of which they had actually experienced. The fourth story was fiction; it centered on the subject being lost in a mall or another public place when he or she was between four and six years old. A relative provided realistic details for the false story, such as a description of the mall at which the subject's parents shopped. After reading each story, subjects were asked to write down what else they remembered about the incident or to indicate that they did not remember it at all. Remarkably, about one third of the subjects reported partially or fully remembering the false event.

Given the dangers of mistaken convictions based on faulty eyewitness estimony, how can we minimize such errors?

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Source material from Scientific American


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