Thousands of police departments use face composite software to help create a picture of crime suspects. You’ve probably seen one of the systems in use on TV: witnesses build a picture of the suspect by choosing each individual facial feature — hair, eyes, nose, and so on. But what happens when the suspect is captured and the witness is asked to identify the real perpetrator in a lineup? Does the witness remember the actual face they saw at the crime scene, or the composite face created at the police station? A recent study has found that the process of creating a face composite can have a dramatic impact on the memory of a real face.

Research in face perception shows that we tend to remember faces not so much based on the individual features, the way face composite software works, but based on the relationship between the elements of a face. It makes sense: after all, we can still recognize our friends if they get a haircut or shave off their mustache. A team led by Gary Wells reasoned that if crime witnesses spend 20 minutes recreating a face they saw for perhaps only a few seconds at the crime scene, the face they create might supplant the real thing in memory. While a few studies have tested this notion previously, they were typically done on too small of a scale to have conclusive results. In an effort to find a more definitive answer, Wells’ team created two studies with over 300 participants.

In the first experiment, 150 participants were divided into 3 groups. All the “witnesses” were told they were going to be participating in a study on “perceptions of people.” They were first shown one of 50 different photos and asked to rate it on 10 different traits, such as intelligent, humorous, and so on. Next the picture was removed and they were asked to write a description of the face. The first (control) group was sent home and asked to return 48 hours later. The second group was asked to use FACES computer software, the most popular face composite software, to create a composite image of the face they had seen. The third group didn’t create the composite, but was instead shown a composite of the face they had seen, created by one of the participants in the second group.

Finally, in 48 hours, all the participants returned and were asked to pick the photo they had previously seen out of a lineup of six photos, which had been selected for similar general characteristics to the “suspect” (this is standard police procedure — it wouldn’t be fair, for example, to place a black suspect in a lineup of white people, or a bearded suspect in a group of clean shaven people). They were initially told that the suspect may or may not be in the lineup, and so the correct answer might be “none of the above” (again, standard police procedure). If no suspect was selected at this point, then participants were asked who they would pick if they had to make a choice. Here are the results:

As you can see, the results are dramatic. Just 10 percent of the people who built composites correctly identified the suspect initially. Even when forced to make a choice, their accuracy only climbed to 30 percent, not much better than chance. By contrast, the control group, who had only seen the original photo, was 84 percent accurate originally, and 94 percent when forced.

But these results aren’t ideal. Witnesses see real crimes, not static photos. And misidentifications when the perpetrator is in the lineup aren’t catastrophic, because the “filler” lineup participants are not going to be prosecuted — the problem comes when the police arrest the wrong suspect and he or she is picked out of a lineup. In the second experiment, Wells’ team addressed these issues in a new experiment by showing participants a simulated crime video, and by using some lineups that didn’t actually include the perpetrator.

As before, the 200 “witnesses” were told that they were in an experiment on “perceptions of people.” They were told to watch the crime video closely because they’d be asked questions about it later. When the video was over, they were told that the video showed a person planting a bomb in a building’s air shaft, and they would need to write down a description of the “roof bomber,” whose face had been clearly visible in the video for 21 seconds. Half the participants were sent home, and the other half made composites, as before.

48 hours later, all participants were called back and asked to identify the perpetrator in a lineup, exactly as before. This time, however, half the lineups didn’t included the perpetrator at all. Here are the results:

There was no difference between the lineups with and without the perpetrator, so that data is not presented here. As you can see, however, those who made composites made many fewer correct IDs when the perpetrator was present, and also selected the incorrect suspect significantly more often, even when the perpetrator was not present in the lineup. In this more realistic scenario, creating a composite face still puts the witness at a whopping disadvantage compared to people who had only described the ciminal verbally.

Wells’ team is careful to point out that face composites can still be an important crime-fighting tool. If there are several witnesses, one could make the composite and the others could ID the suspect in a lineup. A face composite may be the only way police have of locating the suspect at all; when captured, other evidence might link the individual to the crime.

However, Wells et al. do point to an older technology which may need to be revisited: the police sketch artist. Perhaps if a sketch artist creates an image based on a witness’s description instead of relying on composite-creating software, the witness may still accurately remember the perpetrator.

Wells, G.L., Charman, S.D., & Olson, E.A. (2005). Building face composites can harm lineup identification performance. Journal of Experimental Psychology: Applied, 11(3), 147-156.