Prosecutors love eyewitnesses. They can be very effective at convincing a jury that someone really did commit the crime they stand accused of. There lies the problem. Sometimes they are too convincing, even when they are wrong.
It’s not that an eyewitness goes onto the stand to purposefully deceive the jury (although there are occasions when that can happen). Rather, it is that people tend to assume what they say is the truth. Why would anyone waste their time going up on the stand otherwise?
Eyewitnesses usually think they are telling the truth
Eyewitnesses can get things wrong for several reasons:
- Poor sight: Maybe their view of events was partially obscured. Perhaps they were too far away to get a really good view. Or perhaps their eyesight is not as great as they believe.
- Seeing what they expect: Some people have biased views about certain groups. It may come from one personal experience, from the society they grew up in or the company they keep. For instance, a person who sees a tussle between a teenager in a hoody and a guy dressed in a suit might instantly assume that the teen in the hoody is the aggressor.
- Fed information: Police officers can sometimes unintentionally (or intentionally) transmit their opinions to an eyewitness through their words, looks or actions. If the eyewitness picks up on that signal it may influence what they believe they saw.
People often believe a memory is fixed. It’s not always. Memories can change over time making it hard for a person to know what they really saw. The more they repeat their version of events the more it becomes ingrained in their head as the truth even if it is not the truth.
If you have an eyewitness willing to testify against you, learning more about how to challenge their version of events could be crucial to your defense.