You may have heard something about the unreliability of eyewitness testimony. The chances are good that what you heard was in conjunction with a wrongful conviction. In the past, prosecutors often used eye witness testimony as the main evidence against accused individuals and ended up winning those cases without much physical evidence.
According to the National Center for State Courts, there has been extensive evidence found through research that eyewitness testimony is not fair or effective evidence because it is unreliable for several reasons.
Outside influences
Witnesses often can have their perception of situations influenced by outsiders. Officers may either consciously or unconsciously influence the memory of a witness or may set up a situation to encourage incorrect recall of a situation or to push you to remember something in a certain way that benefits their case.
It is very easy to influence your recall if you are unsure of what you saw. Because officers want to get answers, they may lead you to remember a certain way, even if they do so without the intent to taint your memory.
Bad memory
Human memory has many flaws. Your brain has a variety of ways it can trick you into thinking you remember something that is not accurate and sometimes not even real. No matter how confident you are that your memory is correct, there is always the chance that it is wrong.
Perception
Compounding this is the issue of perception. Each person may perceive or see something differently. They may have a different view of something due to their physical location or personal background. Two people can see the exact same thing and come up with wildly different accounts.