Faculty and Staff

There is substantial controversy over the extent to which social science should be used in jury selection. Underlying the debate are two competing interests in the make-up of a jury: a privilege to strike prospective jurors on subjective grounds, which supports scientific jury selection, and a collective interest of citizens to be free from exclusion from jury service, which does not. While the incommensurability of the interests precludes resolution of the controversy in the abstract, specific solutions are possible. Using the example of selection of jurors based upon their respective levels of extraversion, we describe how the competing interests frequently do not apply to concrete cases. In the subsequent analysis, we show that, rhetoric notwithstanding, a normative preference for adhering to tradition and institutional inertia are the primary instrumental considerations for determining whether peremptory challenges based upon personality traits like extraversion ought to be allowed. Consistent with this analysis, we conclude that the practice of striking jurors based upon estimates of such personality traits is appropriate.

The knowledge of experts presumably affects their credibility and the degree to which the trier of fact will agree with them. However, specific effects of demonstrated knowledge are largely unknown. This experiment manipulated a forensic expert’s level of knowledge in a mock trial paradigm. We tested the relation between low versus high expert knowledge on mock juror perceptions of expert credibility, on agreement with the expert, and on sentencing. We also tested expert gender as a potential moderator. Knowledge effects were statistically significant; however, these differences carried little practical utility in predicting mock jurors’ ultimate decisions. Contrary to hypotheses that high knowledge would yield increased credibility and agreement, knowledge manipulations only influenced perceived expert likeability. The low knowledge expert was perceived as more likeable than his or her high knowledge counterpart, a paradoxical finding. No significant differences across expert gender were found. Implications for conceptualizing expert witness knowledge, credibility, and their potential effects on juror decision-making are discussed.

The essential tasks for an expert witness are to be prepared, to be effective and credible on the stand, and to manage well the demands of cross-examinations. Most novice experts are excessively anxious about their testimony. Effective experts are well-oriented to the legal and scientific context of court testimony. This chapter reviews research-backed tips for preparing for expert testimony.