While the technological advances of DNA testing in the past decade have improved the criminal justice system as a whole, there are two specific areas it has made the largest impact: cold cases and the wrongfully convicted. There has been story after story of how DNA found on a murder weapon or at the scene of the crime proves the innocence of an incarcerated person. Those stories typically have a common thread: the guilty verdict hinged on an eyewitness account.
In a new study, published in Memory & Cognition, researchers in the UK put eyewitnesses to the test.
“Having a stereotypically ‘criminal’ or threatening appearance has long been established to be a disadvantage in the judicial system, both in terms of the likelihood of initially being arrested and in terms of courtroom sentencing,” said co-author Terence McElvaney, Ph.D. student in the department of biological and experimental psychology at Queen Mary University. “What we wanted to establish through this new research was whether some people are also more likely to be falsely identified as a criminal because they naturally have a more threatening appearance.”
Contrary to the researchers’ expectations, their study showed no eyewitness bias toward selecting people with threatening facial characteristics or muscular bodies. However, suspects with highly muscled, “threatening” bodies were most accurately identified by eyewitnesses in line-ups.
For the study, 200 adult volunteers took part in three separate experiments. In each one, participants were presented with either the outline of a violent crime, neutral information, or no background information. They were then shown a realistic computer-generated image of the male suspect (target) and asked to identify him from a selection of images that varied in facial threat or body muscle. All faces in the dataset were white men, converted to grayscale.
Experiment 1
Participants were divided into two teams, with one group told the person they were about to see was involved in an armed robbery; the other told the aim of the experiment was to see how accurately they could identify unfamiliar people. The groups completed 20 trials in total, identifying a different suspect each time from a selection of faces and body shapes with blurred heads. In each case, the target image was shown for one second, followed by a blank screen for one second, followed by the line-up.
Experiment 2
This experiment introduced a distractor task adding a five-minute delay between participants seeing the target image for 30 seconds and trying to identify it. Contributors were divided into three categories: in the crime and neutral groups, they were presented with background information, such as a shop robbery resulting in a murder, or someone purchasing a winning lottery ticket. The final group was told to study the person for later identification. Fixation dots and a random noise mark were also added to the start of each trial to break concentration. This time, faces or bodies were shown individually with those taking part responding Yes or No to the question: “Did that face/body EXACTLY match the one you previously studied?”
Experiment 3
Three groups of participants with different context were given 30 seconds to study the target, then following a distractor task lasting 10 minutes, were asked to identify him from a line-up of bodies only, from which the perpetrator was missing.
Conclusions and limitations
While the authors hypothesized that more threatening faces and larger bodies would be selected when the perpetrator was presented in a criminal context—rather than in a neutral context—that was not the case. According to the study results, giving criminal background information about the suspects did not significantly influence participants’ memories.
“Participants viewing images of alleged violent criminals were no more likely to overestimate the facial threat or musculature of the target stimuli than those who studied the targets in empty or neutral contexts,” the authors explain. “These results suggest that, although errors of eyewitness identification can or do occur, they may not be driven by systematic biases related to how threatening a criminal is later recalled.”
However, a substantial limitation of the study results exists: all faces in the dataset were white men. Therefore, while this study can be used to inform conclusions on white persons eyewitness accounts, the results are not applicable to Hispanic, Black or other minorities—the ones whom have traditionally been impacted by eyewitness bias.