WASHINGTON - Fingerprints, DNA matches and fibers may be more reliably objective indicators that a suspect committed a crime, but, studies have found, for most jurors, nothing beats the confident testimony of an eyewitness, even when the eyewitness is completely wrong. Research has shown that incorrect eyewitness identifications account for more convictions of innocent persons than all other causes combined. Now a new study reported in the June edition of the Journal of Applied Psychology, published by the American Psychological Association (APA), provides even further evidence that eyewitness testimony may not deserve the confidence that many jurors have in it.
Psychologist Gary L. Wells, Ph.D., and Ph.D. candidate Amy L. Bradfield, of Iowa State University, conducted two experiments to test the degree to which eyewitnesses are influenced by the positive or negative feedback they get immediately after making an identification. Providing such feedback, the authors say, is a common police practice. Their findings were both unexpected and alarming.
In the two studies, which involved a total of 352 people, the researchers had participants watch a grainy surveillance camera videotape of a person who later shot and killed a store security guard. They were then presented a photospread of five faces that did not include the actual gunman, but were asked to identify the man they had seen on the videotape. After the participants in the first study made their identifications (which were, of course, always wrong), they were randomly told: "Good. You identified the actual suspect in the case." or "Oh. You identified number X. The suspect is number Y." or they received no feedback. The participants then filled out a form that asked a long series of questions about their identification, asking how good a view they had of the gunman, how well they were able to make out specific features of the gunman's face from the video, how certain they were of their identification at the time they made it, how easy or difficult it was to figure out which photo was that of the gunman, how willing they would be to testify in court that the person they identified was the gunman, etc.
As expected, those who received positive feedback were more confident of their identification than those who received either negative feedback or no feedback at all (even though all participants were equally wrong). However, the positive feedback about the supposed accuracy of their identification seemed to make them remember almost everything about their identification differently. That is, in addition to being more confident of their choice of photographs, they also remembered having a better view of the culprit, having paid greater attention to the videotape, having had an easier time making the identification, needing less time to make the identification and being better able to make out details of the culprit's face than those who received negative feedback or no feedback. In other words, positive feedback distorted the witnesses' reports of almost every aspect of the identification process. It served, the authors say, "to manufacture credible witnesses from a pool of inaccurate witnesses who were not particularly credible on their own. We are alarmed at these findings."
The second study, which was a variation of the first, also found that while most eyewitnesses denied that positive feedback had any influence over how they recalled making their identifications, it did have influence nonetheless. But the second study also found a potential antidote to the influence of positive feedback: asking questions before giving feedback. In this study, some participants, randomly selected, were asked how confident they were about their identifications before receiving any feedback. The authors say asking such a question -- and probably others - might help prevent eyewitnesses from being unduly influenced by positive feedback.
The authors say they see no reason why the effects seen in these experiments would somehow disappear in real cases. In fact, they say, feedback might even have stronger effects in real cases than it had here. Another reason for alarm is the fact that the criteria most courts use to determine the likely accuracy of an eyewitness's identification of a criminal suspect - presumably to keep eyewitnesses who are not credible off the stand - would have no effect in detecting or countering feedback-caused memory distortion.
Based on these findings, the authors strongly advocate that lineups and photospreads be supervised by someone who does not know who the suspect is and that eyewitnesses at least be asked about their confidence -- and have their responses recorded -- "at the time of the identification, rather than after there is an opportunity for other events to influence the eyewitnesses' confidence and other judgments."
Article: "'Good, You Identified the Suspect': Feedback to Eyewitnesses Distorts Their Reports of the Witnessing Experience," by Gary L. Wells, Ph.D., and Amy L. Bradfield, Iowa State University, in the Journal of Applied Psychology, Vol. 83, No. 3.
(Full text available from the APA Public Affairs Office.)
Gary L. Wells, Ph.D., can be reached at (515) 294-6033 or at glwells@iastate.edu
The American Psychological Association (APA), in Washington, DC, is the largest scientific and professional organization representing psychology in the United States and is the world's largest association of psychologists. APA's membership includes more than 155,000 researchers, educators, clinicians, consultants and students. Through its divisions in 50 subfields of psychology and affiliations with 58 state, territorial and Canadian provincial associations, APA works to advance psychology as a science, as a profession and as a means of promoting human welfare.
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Journal of Applied Psychology