In a recent study by Huff (1987), who examined 500 wrongful convictions, the conclusion was that 60% of these wrongful convictions was due to faulty eyewitnesses. There are several reasons why the accuracy of eyewitnesses is compromised.
First, no one's memory is perfect. This is a fact that we must never forget. Second, on account of the faultiness of human memories, what tends to happen is that the human mind supplies the missing pieces from expectations, biases, and external sources like what a person has seen in the media. This affects accuracy. This is a serious problem, because it can lead to wrong iidentifications.
Second, the mind also has the habit of also conflating (i.e., combining) other memories to make the most recent memory more cogent or believable. This affects accuracy.
In light of these two propensities of the human mind that affect accuracy, it is no wonder that there are many wrongful identifications. In light of this, eyewitnesses evidence must be carefully weighed.