Memory and Witness Identification

There are now more than 300 cases of DNA exoneration in the United States—cases in which DNA evidence, available only after a trial was over, has shown incontrovertibly that the courts had convicted the wrong person. In each case, someone totally innocent spent years in jail, while the actually guilty person walked around free. In many cases, the innocent person, now exonerated, had been on death row awaiting execution. If the DNA evidence hadn’t been available, the wrong person would have been executed. 

In the vast majority of these cases, the mistaken conviction can be traced to bad eyewitness evidence: The juries had (understandably) been persuaded when an eyewitness confidently pointed to the defendant and said, “That’s the man who raped me” (or “robbed me” or “shot my friend”). But in case after case, the witnesses were wrong, and the jury’s decision was correspondingly mistaken. 

It’s crucial, therefore, to ask what we can do to avoid these incorrect identifications, and we can be guided by what we know about memory’s operation in general and about memory for faces in particular. For example, research has identified a number of factors that can undermine the accuracy of an identification, and we can use these factors as a basis for deciding which identifications need to be treated with special caution. As just one illustration, we mentioned in the Cognitive Psychology and the Law essay for Chapter 3 that eyewitness identifications tend to be less accurate when the witness and the perpetrator are of different races. This suggests a need for caution when interpreting a cross-race identification, and this by itself can potentially help the courts to make better use of eyewitness evidence. 

Other research has asked what steps we can take to diminish the chance of eyewitness error. For example, psychologists have offered advice on how a police lineup should be constructed—that is, what faces should be included, in addition to the suspect’s—to minimize the chance of error. Evidence makes it clear that a well-chosen lineup can markedly decrease the chance of witness error, and so it is crucial, for example, that the other faces in the lineup be consistent with the witness’s initial description of the perpetrator; otherwise, some lineup members may not be taken seriously as real choices for the witness, and this can guide the witness’s attention to the suspect’s picture, increasing the risk of a false (incorrect) identification. 

We can also change the instructions given to witnesses. It is important, for example, to remind witnesses before viewing a lineup that they are under no obligation to make a choice, and that the perpetrator’s face may or may not be among those presented. This instruction seems to have little effect if the perpetrator is actually present in the lineup—in essence, if he’s there, you’re likely to spot him. But if the perpetrator is not present in the lineup (i.e., if clues have led police to the wrong person), then this instruction is remarkably effective in protecting the innocent: Merely telling the witness that “the perpetrator may or may not be shown here” and “you’re under no obligation to choose” seems, in some studies, to cut the risk of a false identification in half. 

A different proposal concerns how the faces are shown. In a standard lineup, the witness is shown all six faces at once and must choose from among the group. In a sequential lineup, the witness is shown the faces one by one and must make a yes or no judgment about each one before seeing the next. This procedure has been controversial, but even so, it does seem to decrease the number of false identifications, and so may be an improvement on the standard (simultaneous) presentation. 

These various points—including the procedural improvements—offer a considerable potential for improving eyewitness accuracy. It is therefore gratifying that law enforcement is taking these steps seriously with a real prospect that we can use what we know about face memory and eyewitness behavior to improve the criminal justice system.

What are some reasons why an eyewitness might “recognize” and identify an innocent person in a photo lineup? How might a false recognition affect subsequent courtroom testimony?
What steps can be taken when constructing and presenting a photo lineup to minimize the chances of a false identification? Can you think of any beyond those described in the reading?
Would it be better to use a photo lineup consisting of those who fit the verbal description provided by the witness or of those who bear some resemblance to a suspect who appears in the lineup? Justify your answer.
In Chapter 11 we learned how long-term visual memory may be represented in terms of propositions, rather than perceptual representations. How might this kind of visual memory lead to identification errors in a photo lineup? How might you counteract or avoid those errors?
The two videos in this module feature two artists with extraordinary visual memory. But do they exhibit eidetic memory or photographic memory? What is the distinction? How would you expect their brains to differ from the brains of those without such extraordinary abilities?