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It is tragic that eyewitness testimony remains one of the most influential pieces of evidence heard by juries; the Association for Psychological Science points out that “convincing” and “accurate” are two often unrelated qualities in a witness’s account. 

Since a conviction could ultimately come down to the correctness of an eyewitnesses’ memory, psychologists work to find the reasons why they are frequently unreliable. 

Why witnesses believe their memories 

A memory is not a video clip. Instead of storing images, frame by frame, the mind creates a version of events that is usually a combination of truth and fabrication. Each time a person recalls a memory, it often changes subtly based on new external information. This distortion almost always happens unconsciously, too. People genuinely believe that their memories are entirely accurate, even when they are not. 

Psychologists believe a few additional factors could affect the accuracy of eyewitness identifications: 

Confirmation bias 

When people successfully recall a face, they are likely to remember those successes. Conversely, people are more apt to forget how often they do not know something. Called confirmation bias, it can invoke a false confidence in eyewitnesses. 

Stress-induced memory suppression 

People are also inclined to believe that a distressing experience like a crime is so impactful that they should instinctively remember every detail. However, quite the opposite is often the case. Psychologists believe that stressful situations actually suppress the formation of memory. Witnesses then are susceptible to “creating” the memory later based on outside suggestions from sources like law enforcement. 

Cross-racial misidentification 

Statistics also show that people generally have more difficulty recalling the features of a person of a race other than their own. The Innocence Project found that of all those convicted based on eyewitness testimony and later exonerated by DNA evidence, over 40% of the errors were cross-racial.