That eyewitness sketch looks a bit too accurate…

I watch a lot of crime shows. I don’t know what it is about them that makes them so entertaining but I just can’t seem to tear myself away. Currently I’ve been binge-watching NCIS, and I noticed something that happens a lot when they’re getting eyewitness reports on a suspect. So many times they’ll show a sketch of a suspect’s face, recalled from the witness’s memory hours, sometimes days after the incident, and it ends up looking nearly exactly like the person they catch. That is just so hard for me to see as believable. Very few people have memories good enough to make recalling all the details perfectly a possibility. Even if we are extremely confident that what we are remembering is what we actually saw, chances are we’re at least a little bit off. As soon as we experience something, our mind immediately begins to forget the details. Now, I strongly believe our ability to remember things is greatly influenced by stress as well. So, how much to eyewitnesses to crimes, especially murders, really remember?

So first off, we need to form a null and an alternative hypothesis. Our null hypothesis is that the accuracy of an eyewitness’s claim is not affected greatly by high emotional levels, such as stress. Our alternative is that the accuracy of an eyewitness’s claim is affected greatly by high emotional levels.

This study about eyewitness memory was done using a group of people who had witnessed a shooting four to five months before the study. 21 people witnessed a shooting which killed one person and seriously injured another; they were all interviewed by the police during the investigation. The shooting happened on a major street outside of a gunshot and so each of the 21 witnesses saw the incident from various vantage points. 13 of these witnesses agreed to participate in this study months later. The researchers took into account inevitable losses or changes in the memories of the participants by looking at the interviews done by the investigating officers in addition to the ones the researchers themselves conducted. The results of both of these interviews ended up showing that the witness’ reports were usually very accurate to the actual incident. The lowest accuracy level, at around 76% for the police interviews and 73% for the research interviews, came from the descriptions of people, while the object descriptions resulted in about 89% accuracy on average for the police and 85% for the researchers. I noticed that there wasn’t much change in the eyewitness reports even after 4 or 5 months. I believe this may be due in part to the fact that people wouldn’t often forget the details of an experience such as this, but also because the researchers asked quite a few in-depth questions that had to have led to memories resurfacing. In regards to stress, the five witnesses who had direct contact with something pertaining to the shooting ended up reporting the most amount of stress during and after it. In this study, stress is recorded as a confounding variable. This unfortunately means that stress was not greatly taken into consideration during the research. However, the witnesses who reported the most amount of stress had memory accuracy levels that were around 70-80%, which was the average. The results of this study do show that there is some inaccuracy in eyewitness reports due to the eyewitnesses being unable to retain some details in their memories, particularly after some time has past. However, the inaccuracy is not as great as I would have thought it would be, which is reassuring to hear. And, it does not seem to be that stress or other such high emotional levels affected the witness’ abilties to recall details of the incident. At least that means that we can usually trust eyewitness accounts to be accurate in most cases.

Police line-up ... a famous scene from the film The Usual Suspects.

Now, this article is a review of a few other studies that have been done on stress as a factor in eyewitness reports. Quite a few of the studies themselves were done around the 1960s to 80s and each was published in credible research journals. The review states that many studies showed that memories before and after an event are occasionally less accurate or forgotten altogether (at least for a temporary time) if the witness was at a high emotional level at the time of the event. But on the other hand, details of the event itself were usually very well retained, even when the event caused high emotional levels. These various studies show that there is less loss of detail in high emotion causing events than there is in events where the witnesses did not feel high emotional levels. So it seems that high emotion responses to events actually increase a witness’s ability to accurately recount details, not decrease it.

I suppose this means that I was wrong. Stress and other such factors do not seem to hinder a person’s ability to recall details of an event. This means that we must accept the null hypothesis. I am, however, disappointed that I wasn’t able to find more studies done on a topic like this one. I would think that it would be an important subject, especially to forensic scientists and investigators. It’s possible that this topic suffers from the file drawer problem, and that studies have been done that were never published.


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1 thought on “That eyewitness sketch looks a bit too accurate…

  1. Daniel J Lehecka

    Not entirely related to the topic of emotion, but this post made me think of all the terrible witness sketches that I’ve seen online. The one that comes to mind is this one, but interestingly enough the sherrifs department actually said that this picture helped them confirm that they suspect they believed was the correct one. But more on topic to your point, I think if it’s a major crime then those people would actually be more likely to remember if it caused noticeable emotional strain on them. It would be a moment that they would never forget, and might have a more clear mental history of it as a result.

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