Memory affects the accuracy of eyewitness identifications because eyewitnesses often think they remember things that really did not happen. Because memory can be faulty, eyewitness identifications can be faulty as well.
Many people tend to think that we remember things exactly as they happened. People believe that we can simply play back an incident in our mind and see it just as it occurred in real life. The problem is that memory does not work this way. Instead, our memories are constructed by our brains, which put together pieces of things we really do remember but which also have to fill in blanks in our memories. There are things that we simply cannot remember even if they did happen to us.
In addition, our memories are subject to suggestion. If people tell us or even hint to us that something might have happened, we are able to construct false memories to go along with what we have been told. This makes eyewitnesses very susceptible to making mistaken identifications if the police do anything (even inadvertently) that tampers with the witnesses’ memories.
Memories are incomplete and easily falsified. Because of these problems, eyewitness identifications can often be erroneous.