When you watch a video of a past event, it is recorded as perfectly as the video camera could manage. When you think of a memory of a past event, odds are that you think of it the same way. You imagine that the memory in your head is a perfect rendition of what actually took place, recorded by your brain in the same way that a video camera or a smartphone can record a video.
But this isn’t actually how human memory works. It’s malleable and it changes over time.
A common example of this is when people think they have “memories” of pictures they’ve seen of past events. Someone may say that they have a memory of sitting in the living room with their great-grandparents on Christmas morning 30 years ago, only to find that there is a picture of that morning in their photo collection.
Why does this matter for criminal defense cases?
The problem here is that in the majority of exonerated cases – where someone was convicted of a crime and DNA evidence later showed that they did not commit the crime – eyewitness testimony was the reason for the conviction. Since DNA evidence can prove that the conviction was false, this suggests that the eyewitnesses were wrong.
In some cases, it could be that an eyewitness was lying intentionally. But because memory can change, it’s equally possible that the eyewitness thinks they are giving an accurate account when they are actually getting it wrong.
This adds a high level of complexity to a criminal case, and it’s one reason why those facing charges need to know exactly what legal defense options they have at their disposal.