Eyewitness Testimony, Accuracy Of

History of Research on Accuracy of Eyewitness Testimony

For many years, psychologists have been trying actively to understand how and why eyewitnesses make mistakes. Hugo Munsterburg published his groundbreaking volume on the topic, titled On the Witness Stand, in 1906. This book, based on basic memory research, detailed how eyewitnesses were prone to a number of errors and did not have the perfect memories the legal system often assumed. Although Munsterburg's book stimulated a great deal of discussion after it was published, it was largely dismissed by the legal system because it did not describe research that had been done specifically on eyewitnesses to crimes.

Contemporary Research

Hundreds of more recent studies have explored the accuracy of eyewitness identifications. The basic distinction these researchers have made is between system variables, factors the legal system can control, and estimator variables, factors the legal system cannot control. With system variables, one can construct the situation so that errors may be avoided. For example, a biased lineup instruction from the police (e.g., “The guy is in the lineup, all you have to do is pick him out”) will lead to more eyewitness errors than will an unbiased instruction (e.g., “The criminal may or may not be present in the lineup”).

An example of an estimator variable is the race of the criminal relative to the witness. Research has shown a consistent decrease in eyewitness accuracy if the witness and the suspect are of different races. Because this decrement is greater when the majority group member identifies a minority, relative to when a minority attempts to identify a majority group member, some researchers have suggested familiarity with the other group may be the cause of the increased error. Other researchers have suggested that different racial groups focus on different facial features. However, a definitive cause has thus far eluded researchers. Importantly, there is little the legal system can do to alleviate this problem. Thus, many researchers have argued it may be best to focus on system variables, as these are the factors that the legal system will be able to change.

Guidelines for Investigators

Although research in the field has been around for 35 years, it is only recently that practitioners have begun to embrace the findings and change their procedures to avoid errors. In 1999, the U.S. Department of Justice published a landmark set of recommendations on the treatment of eyewitness evidence, titled Eyewitness Evidence: A Guide for Law Enforcement. Then attorney general of the United States, Janet Reno called together the relevant stakeholder groups and asked them to come up with an empirically validated guide for law enforcement that the whole group could [Page 338]support. The final group consisted of 33 members: 17 police officers, 4 district attorneys, 6 public defenders, and 6 eyewitness researchers. The Guide, jointly developed by the legal community and researchers, may represent the most comprehensive and potentially influential work of its type ever developed.

...