Think back to last weekend. What time did you get up on Saturday morning? What did you have for breakfast? What clothes did you wear? Did you go out? Who did you speak to? What were they wearing? What did you watch on the TV? What time did you go to bed?
Chances are, you may well be able to remember some of those details. But perhaps you may not be able to recall them exactly in the right order, or in the right timeframe.
Now imagine that the replies you give could affect whether someone is innocent or guilty of a crime. Your testimony could demonstrate that they were with you at a certain time, and not at the scene of a crime. How confident would you be that your recall of the events was correct.
And what if the weekend in question occurred more than a year ago? Still confident?
Many people have been convicted of crimes with the “help” of eye-witness testimonies. This form of evidence still plays a major role in many court cases, and jurors can be heavily influenced by eye-witness accounts.
Yet studies have shown that eye-witness accounts cannot always be relied on. The way we recall our memories is complex. Our brains do not replay memories like a video recorder. Our recall can be influenced by many things: the stress of the event being recalled, how those recollections fit into our experience and conventions of the world we live in, and also on the focus of the recollection. We tend to filter out what we perceive to be unimportant. We reconstruct the memory according to what we believe happened. This does not necessarily mean our memories are false, but it is an individual perception, rather than fact.
And if a weapon is involved in the event being recalled, eye-witness descriptions of the person holding the weapon have been shown to be even more unreliable. A 1987 study showed a group of people two short films of the same man. In one film, the man was holding a cheque In the other film, he was holding a gun. The group were able to describe the man far more accurately when he was holding the cheque. The description of him when he was holding the gun was much less accurate, as the group’s attention was focused on the gun.
The unreliability of eye-witness testimonies has been recognised since the 1930s. Much of the unreliability stems from the way we process memories. A simple experiment carried out by psychologists, asking groups of people to retell a story they had just been told, resulted in varying interpretations. Facts were left out or altered to fit more precisely with the conventions familiar to the story-teller. None of the misrepresentations was deliberate, but rather a result of the fallibility of our memory.
Despite all this, eye-witnesses are still considered to be a vital part of the evidence process. Cases have been won and lost on the recall of one person. But more importantly, lives have been ruined by the acceptance of those memories as fact.
Have a look at this short video to test your powers of recall: http://www.youramazingbrain.org/testyourself/eyewitness.htm