Testifying on eyewitness reliability: Expert advice is not always persuasive.

Maass, A., Brigham, J. C., & West, S. G. (1985). Testifying on eyewitness reliability: Expert advice is not always persuasive. Journal of Applied Social Psychology, 15, 207-229.

This study investigates the impact of different types of expert testimony regarding the unreliability of eyewitness identification. In two hypothetical court cases involving eyewitnesses, expert testimony was presented that was either sample-based (presenting the results of a research program on eyewitness identification) or person-based (presenting information about the particular eyewitness under consideration); the expert either offered causal explanations for his unreliability claim or failed to do so. Two additional control groups (with and without eye-witness identification) were not presented with any expert testimony. The results indicate that subjects who had been confronted with an expert statement made more lenient judgments about the offender but did not discount the eyewitness identification completely. Sample-based information had a moderate impact on the subjects’ judgments, regardless of whether or not causal explanations were given. Person-based testimony was the most influential type of expert advice when a causal explanation was provided but the least influential one when no reasons were given. The practical (international differences in admissibility of expert testimony) and theoretical implications (processing of base-rate information) of these findings are discussed. Strong impact of eyewitness identification on conviction rate. Expert testimony reduced impact of eyewitness identification when it included causal explanations. Longer deliberation when expert testimony provided, especially when it did not include causal explanations.