If accused of a criminal offense, you may feel hopeful you can prove your innocence. Then the prosecution announces it has a witness who places you at the scene of the crime. Witnesses have been vital to many prosecutions over the years. People have been put behind bars and sentenced to death on account of an eyewitness testimony. The problem is eyewitnesses are often wrong.

You may wonder why someone is willing to say they saw you if they did not. Except for the odd occasion where a witness does this to save themselves or settle a score, they usually believe they did see you.

Our memory is not as accurate as we think. People tend to think memory is like a snapshot taken with a camera, preserving history forever. Yet it is not. Memories are dynamic, not static.

Maybe your mom keeps a photo album of your childhood. Perhaps there is a picture of you in a particularly hideous outfit when you were 6 years old. Just looking at it, you can feel the embarrassment come flooding back. You can remember the touch of crinoline against your skin and the tantrums you had when forced to wear it. Yet, most likely, you do not actually remember that moment in time or that outfit. What has happened is your mom has pulled out that photo so often that you have built up an image of it, and it stored it in your memory as if it were real. You know you disliked that outfit because your mom told you, not because you remember disliking it.

If you face criminal charges, your defense counsel can challenge the validity of a witness’s testimony. They may convince a court and the eyewitness themselves that the so-called memory is merely something repeated so often that they have stored it as if it were real.