A comparison of three studies of the influence of expert testimony on jurors

Three conceptual replications of the effects of expert testimony on jurors' decisions and behaviors were compared. Taken together, these studies demonstrated significant increases in jurors' scrutiny of the evidence presented to them and significant reductions in their beliefs in the general accuracy of eyewitness testimony. The overall effect of expert testimony had a combined probability ofp=.0000084. This means that these combined results would occur by sampling bias alone less than one time out of 100,000. Expert testimony accounted for 3% of the variance in verdicts and 68% of the variance in the time jurors deliberated about eyewitness testimony. Several implications of these findings for psychologists investigating eyewitness identification and for the criminal justice system are discussed.I would like to thank James V. Devine, Judith P. Goggin, Elizabeth F. Loftus, and Gary L. Wells for their valuable comments on an earlier draft of this article.