Humans are evolutionarily designed to trust our memories. Our ancestors had to remember a variety of locations, details about other people, and community norms. This memory helped them effectively hunt and gather, recall which group members could be trusted, and when to engage in or refrain from different activities. If a human failed to remember just one of thousands of crucial pieces of information, it could spell their doom. Hence, memory evolved to be one of the most powerful and important tools for a longevity-driven society. Due to this evolutionary history, we have come to trust that our memory is accurate, and in many ways it is.
In the context of eyewitness testimony at criminal proceedings, however, memory is frequently revealed as less than reliable. There are several phenomena at play that lead to faulty memories being recounted by eyewitnesses. One prominent example is the misinformation effect. The misinformation effect is a phenomenon in which a person’s memories become erroneous due to exposure to incorrect information between the original event and the time at which the memory is recounted (e.g. in a police interview or in court). For example, if A sees B stealing a red bike, and then A talks to C (a third party who also witnessed the event), who confidently says the bike was blue, the conversation may cause a reshaping of A’s memory regarding the color of the bike. This can happen with a variety of aspects of an event, including what another person did, what they looked like, and the surrounding circumstances. Numerous studies show that this phenomenon exists, and that it plays a relevant role in many eyewitness testimonies.
Speaking more broadly, a number of studies have shown the lack of reliability of eyewitness testimony in court proceedings [1]. For example, a 2006 study found that in at least 75% of the first 180 DNA exoneration cases involved eyewitness error, and experts estimate that over half of all wrongful felony convictions involve eyewitness error [2].
But if eyewitness testimonies are so unreliable, why do we still rely on them? The short answer is because we have to. A study published in 1987 concluded that just under 80,000 criminal trials every year in the United States are cases in which eyewitness testimony is the primary or sole evidence against the defendant. This number is too large to dismiss all cases in which eyewitness testimony is the primary or sole evidence against the defendant.
The good news is that there is an upshot to all of this. The more we know about the fallacies of human memory, the more we can combat the problem of wrongful convictions. Having law enforcement engage in more careful data collection with witnesses and lawyers engage in more effortful questioning of witnesses can root out some problems caused by phenomena such as the misinformation effect. Interviewing witnesses as soon as possible and taking detailed notes can also help combat potential seeds of the misinformation effect; witnesses will have less time to communicate with other people and, thus, risk contaminating their recollection of an event. Lastly, Given that improperly phrased or suggestive questions can lead to the alteration of memories, questions could also be more purposefully and neutrally designed. Fortunately, much research is being done in this area and judges, law enforcement, and lawyers alike are becoming more aware of the unreliability of human memory. Hopefully, greater awareness will lead to changes that result in fewer wrongful convictions on the basis of eyewitness testimony.
[1] C. Ronald Huff, Wrongful Convictions: Societal Tolerance of Injustice, 4 RES. IN SOC. PROBS. & PUB. POL'Y 99, 103 (1987); Arye Rattner, Convicted but Innocent, 12 L. & HUM. BEHAV. 283, 289 (1988);
[2] Id.