For centuries, eyewitness testimony has been one of the most compelling pieces of evidence when seeking a criminal conviction. The idea that a witness saw the events would seem to remove reasonable doubts. However, the court systems in many states, including Alabama, have begun to question the reliability of this resource.
The problem of memory
The human brain is constantly trying to make sense of the world. When it has an incomplete picture, it naturally fills in details in ways that make sense to the observer. People often create scenarios in their memories where they see what they expect to see.
The effects of stress
In criminal defense circles, how a witness experienced an event is critical in determining how well they observed it. When someone feels that they are in danger, the fight-or-flight stress response activates.
In the natural stress response, the body primes itself for action, producing hormones that increase the heart rate and blood pressure. This same process tends to turn down perception and critical thinking. If a witness felt threatened during an event, their memories of the details may not be reliable.
Witnesses asked to identify a subject may look at a lineup of individuals or photos. The witness in this situation often wants to cooperate and may choose the person who looks the most like their memory rather than making a definite identification.
If the officers involved in the procedure know the identification of the potential suspect, they may unintentionally ask leading questions that push the witness toward their expected conclusion. The court may call the resulting evidence into question.
Changing standards of evidence
Eyewitness testimony will continue to come under scrutiny as researchers understand more about its weaknesses. In the meantime, investigators will increase their focus on DNA testing and other more concrete forms of evidence.