What eyewitnesses are told by law enforcement officials even 48 hours after identifying a suspect from a lineup can significantly influence their confidence in recalling an event and identifying a perpetrator, according to a study in the Journal of Experimental Psychology: Applied (Vol. 9, No. 1) by distinguished psychology professor Gary Wells, PhD, and doctoral students Elizabeth Olson and Steve Charman of Iowa State University.
Previous studies have shown that immediate feedback given to eyewitnesses by law enforcement officials can affect their confidence. As such, many law enforcement agencies now delay feedback given to eyewitnesses by making them wait a day or two to find out if they identified fillers or actual suspects.
In this recent study, researchers tested whether the delay also could have an affect by having 253 college students view a staged crime video and then identify a suspect from a six-person photographic lineup--which did not include the actual culprit. While all the participants identified a culprit, those who received confirming feedback--such as "Good, you identified the suspect"--either immediately after their identification or 48 hours later were the most overconfident about their choices. They tended to overestimate how good their view of the perpetrator had been, how much they were able to make out facial details, and how much attention they had paid to the crime. "These are all distortions caused by giving them feedback," Wells notes.
On the other hand, receiving no feedback whatsoever or receiving disconfirming feedback--such as "No, it was really suspect No. 4"--did not have a significant effect on their confidence.
Wells says he was surprised that eyewitnesses were still affected by the confirming feedback even 48 hours after selecting a suspect from the lineup. "We thought that when we did give them feedback later, they wouldn't be so dependent on it since they were given 48 hours to think about it," Wells says. "But they were found to be just as malleable as they were at the time [when they first identified the suspect]."
Based on the results, the researchers argue for double-blind lineups led by neutral parties who aren't familiar with the actual suspects. That way, no influential feedback can be given to eyewitnesses. Also, the researchers note, it's important for neutral parties to determine how confident witnesses are in their selections by questioning them afterward about their decisions.
"What we're trying to do is make this eyewitness identification process more pristine--with more of the actual thoughts, beliefs and memory of the witness and less of outside agents," Wells says.