Eyewitness identifications of course are not always accurate due to the limitations of human perception and memory. In consideration of these limitations, it would seem appropriate for psychologists who are experts in the area of perception and cognition to educate juries so that they can better evaluate eyewitness testimony. Judges, however, often do not permit psychologists to testify during trial because they believe that the research findings are not beyond the scope of common knowledge already held by the jurors. Presenting the expert testimony, it is argued, would not enhance a jury's ability to weigh the evidence, and might even interefere with the fact finding process which should be left solely to the jury. Additionally, some judges, psychological experts and others believe that research findings are not well enough established to present to jurors as established facts.
In a recent survey of psychological experts, who are familiar with eyewitness identification issues, most respondents agreed that an experts primary responsibility is to educate the jury, and that "jurors are more competent with the aid of expert testimony than without" (Kassin, Ellsworth, & Smith, 1989). Additionally, this study found an agreement rate of 80% among experts for the following topics: the working of questions, lineup instructions, misleading post-event information, the accuracy-confidence correlation, attitudes and expectations, exposure time, unconscious transference, showups, and the forgetting curve. The findings from this survey study are taken by many to indicate that there is a well established body of research in the area of eyewitness identification that experts could be called on to testify. Indeed one legal requirement that the court has to evaluate when considering whether an expert should be allowed to testify is whether there is general agreement or acceptance of the testimony that the expert will present.
Other psychology and the law experts, however, caution that laboratory research findings cannot be generalized in situ (Konecni & Ebbesen, 1986; McCloskey, Egeth, and McKenna, 1986). One limitation of experimental research is that it is conducted in laboratory settings that are only approximations of real world settings. Compared to laboratory investigations, archival research may be a better way to investigate the criminal justice system (Konecni & Ebbesen, 1986).
For a critical exegesis of the use of psychological
testimony in the courtroom, I highly suggest this article: Eyewitness
Memory Research: Probative versus Prejudicial Value
(Ebbesen & Konecni, 1996).
References
Kassin, S.M., Ellsworth, P.C., & Smith, V.L. (1989). The "general acceptance" of psychological research on eyewitness testimony. American Psychologist, 8, 1089-1098.
Konecni, V.J., & Ebbesen, E.B. (1986). Courtroom testimony by psychologists on eyewitness identification issues: Critical notes and reflections. Law and Human Behavior, 10, 117-125.
McCloskey, M., Egeth, H., & McKenna, J. (1986). The Experimental psychologist in court: The ethics of expert testimony. Law and Human Behavior, 10, 1-13.
Wrightsman, L.S., Nietzel, M.T., & Fortune, W.H. (1994).
Psychology
and the legal system. Belmont, CA: Brooks/Cole Publishing Company.