Eyewitnesses are one of the most relied upon pieces of evidence in the trial process. Most jury members do not understand the limitations of eyewitness testimony, and they rely upon it as “fact”. Memory doesn’t function like a video camera: it is malleable and can be influenced by a lot of outside factors. Unlike eyewitness testimony, DNA is conclusive. The Innocence Project states that since 1989, 358 people previously sentenced to death have been exonerated by DNA, and 71% of the convictions involved eyewitness misidentification (APS). It’s important to learn about the fallibility of eyewitness testimony to balance and weigh evidence in trial. This blog will focus on issues in perceiving the crime and memory storage that influence accuracy.
In memory acquisition, many factors, such as level of stress, weapon focus, and physical conditions, can lead to inaccurate memories. The relationship between stress and performance follows a Yerkes-Dodson model. This means that optimal performance (memory) has a moderate level of stress, while very high or very low levels of stress both lead to low performance levels (Simply Psychology). This can be applied to an understanding of eyewitness memory. Those who witness a violent crime will have higher levels of stress, and therefore worse memory, than those who witness non-violent crime. The more stressful the situation, the more likely memory will be inaccurate. In addition, studies have demonstrated that the presence of a weapon decreases recall of the person holding that weapon (weapon focus). In studies where participants are presented with pictures where someone holds a weapon, less information about the person in the picture is accurately remembered compared to participants who are shown the same picture but without a weapon (Psychology). This is due to more focus on encoding the weapon into memory and less time spent identifying characteristics of the person holding that weapon. The physical conditions that eyewitnesses experience also have an effect on memory. For example, low lighting and large distance from the event are both factors that negatively impact memory (Taylor and Francis Online). Obviously, real life witnesses are not always going to have perfect conditions with good lighting and close distance to a crime. It’s important to note the physical conditions that witnesses experience to determine the probability of accurate testimony.
Memory storage processes, such as reconstructive memory and the misinformation effect, can also lead to inaccurate memories. As we encode memories, we construct scripts to connect details that are closely related. These scripts condense information into smaller portions to make encoding simpler. However, recalling memories based on these condensed scripts may lead to inaccuracies. For example, if a person views a scene at a beach, they might recall seeing an umbrella (since umbrellas are often found at beaches), even if there was no umbrella in this scene (Science Direct). When we condense memory into scripts based on prior knowledge and associations, the specific details can be lost. Another factor that impacts memory is the questioning process. Questions may alter a memory if they give information about the memory itself (misinformation effect). In a study by Elizabeth Loftus, participants viewed the same car crash on video (Simply Psychology 1). Participants were asked to recall the accident as if they were witnesses. Groups were asked how fast the cars were going when they smashed/collided/bumped/hit/contacted each other. The difference in the word used to describe the accident affected the estimate of speed. Those who had the question with “smashed” estimated higher speeds than those who had the question with “hit,” even though all participants watched the same video. Later on, a follow-up was conducted (without rewatching the video) and participants were asked if there was broken glass from the accident (there was no broken glass in the video). Participants who had the question with “smashed” earlier in the experiment were significantly more likely to remember seeing broken glass. These results are due to the script these participants built of cars that “smash” into each other being a severe accident. This experiment proves that memory can be altered by questions and information given after the event.
It’s really important to note all of the factors that may influence memory so that we can be more critical of eyewitness testimony. The acquisition and storage processes of information can lead to inaccuracies, and jurors should know the situations in which these inaccuracies arise so they can deduce how much weight to give eyewitness testimony. In the next blog, I intend to demonstrate the factors that influence memory recall and can lead to inaccuracies.