Journal of Applied Psychology 1980, Vol. 65, No. 1,9-15 Impact of Expert Psychological Testimony on the Unreliability of Eyewitness Identification Elizabeth F. Loftus University of Washington The purpose of the present research was to study the influence on jurors of expert testimony about eyewitness identification. In Experiment 1 240 students (all registered voters) acted as jurors and received evidence against a defendant in a violent or a nonviolent case. The major piece of prosecution evidence was the testimony of the eyewitness. Half of the jurors read about the testimony of a defense expert on the reliability of eyewitness identification, whereas half did not. Individual verdicts were reached. The results indicated that there were fewer convictions when expert testimony was permitted. In Experiment 2 120 students received evidence in a hypothetical violent crime and then deliberated injuries of 6 to reach a verdict for or against the defendant. Jurors who had read about the expert testimony spent much more time discussing the eyewitness account than did jurors who had not been presented with expert testimony. The results indicate that one consequence of presenting psychologi- cal expert testimony is an increase in the amount of attention that jurors give to eyewitness accounts, perhaps enhancing their scrutinization. Some pros and cons of the psychological expert testimony are discussed. The unreliability of eyewitness identifica- tion evidence poses one of the most serious problems in the administration of criminal justice. Some known cases of mistaken identification have been rectified before an individual has suffered too much harm. But in other instances innocent persons have been identified, convicted, and even sent to prison on the erroneous word of a fellow citizen. These tragedies force us to ask, What shall be done to protect against the danger of a mistaken identification? One solution is to allow the judge or the jury to hear an expert witness present psy- chological testimony about the factors that This research was supported by grants from the National Institute of Mental Health and the National Science Foundation to E. Loftus. The preparation of this manuscript was facilitated by grants from the Na- tional Science Foundation and The Andrew Mellon Foundation to the Center for Advanced Study in the Behavioral Sciences. The ideas in this paper benefited from discussions the author had with Carl Wagner and John Kaplan. Requests for reprints should be sent to Elizabeth Loftus, Department of Psychology, University of Wash- ington, Seattle, Washington 98195. affect the reliability of eyewitness accounts. The expert psychologist can describe the studies that have been conducted, along with experimental results, on people's ability to perceive and recall complex events. Factors that may have affected the accuracy of the particular identification in the case at bar can be related to the jury. In this way the jurors will have enough information on which to evaluate the identification evidence fully and properly. Such expert testimony, al- though Relatively new, has already been al- lowed in numerous states around the country (Fishman & Loftus, 1978). The basic purpose of any evidence, in- cluding the testimony of an expert psycholo- gist, is to facilitate the acquisition of knowl- edge by the jury, or trier of fact, thus enabling them to reach a final determination. The system of evidence used in American courts rests on the following two axioms: Only facts having rational probative or evi- dential value are admissible, and all facts having such value are admissible unless some specific policy forbids. The trial judge has the broad discretion to decide whether Copyright 1980 by the American Psychological Association, Inc. 0021-9010/80/6501-0009$00.75 9