Eyewitness Memory, Lay Beliefs About

Lay beliefs about factors that influence the reliability of eyewitness testimony have been assessed with a variety of survey and experimental methods. When compared with expert opinion about the effects of these factors, the lay public frequently holds beliefs that would be considered incorrect in the light of psychological research on eyewitness memory.

A brief example provides the framework for understanding the relevance of lay beliefs about eyewitness memory to legal decision making and criminal justice procedures: A man presents a note to a bank teller and tells everyone to get on the floor. A security agent rushes the robber and is shot, but the thief escapes. Six weeks later, a man named Simon Chung is apprehended. His picture is included in a collection of photos that is shown to the teller, the wounded security officer, other employees, and the bank customers. The teller and four customers identify Chung as the robber, whereas the bank security guard and another three employees do not. Chung is charged with the crime and the case proceeds to trial. The prosecution believes that the five eyewitness identifications make up a strong case against Chung. At trial, Chung's defense team presents a cognitive psychologist who, if given the opportunity, will testify that a number of features of the robbery and of the defendant reduce the reliability of the identification evidence. Defense counsel argues that jurors need to be aware of these factors if Chung is to receive a fair trial. The judge considers the expert's testimony and, over the objections of the prosecution, decides that the expert should be allowed to give evidence.

The proffering of expert testimony at trial occurs frequently in common law countries. Judges decide whether an expert will be heard on the basis of several legal criteria, the most important of which for present purposes is the judge's assessment of the levels of lay or juror knowledge about eyewitness testimony. If the substance of an expert's presentation is deemed to be relevant to the case and to be outside the jurors' ken, experience, or their common knowledge, expert testimony intended to inform the jurors will likely be deemed admissible. Only an expert in the specific subject area may provide what is called opinion evidence on the matter. Based on his or her own knowledge and evaluation of the expert testimony, the judge decides whether members of the jury are, as a group, sufficiently informed and, if not, whether the quality and reliability of their deliberations will benefit from an expert's presentation. Given the adversarial nature of common law procedures, it is probable that opposing counsel may also proffer an expert who has a different interpretation of the importance of the relevant eyewitness factors.

Regardless of the decisions made by judges in these situations, there is little research that can tell us whether their assessments of jurors' lay beliefs about eyewitness factors are likely to be correct. Furthermore, although a topic of interest in its own right, few studies have assessed whether judges (or trial counsel) themselves hold correct beliefs concerning eyewitness issues. The question raised here, however, is the following: On what basis do judges decide whether jurors are sufficiently informed (or have “common knowledge”)? Scientific investigations of lay beliefs about eyewitness memory have been conducted and, on occasion, the judges' assessments are informed by descriptions of this line of research.

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