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.

This study sought to investigate the relation between expert witness likeability and juror judgments of credibility and sentencing. Two actors playing expert witnesses were trained to present themselves as high and low in likeability in a standard testimony scenario involving capital trial sentencing. The effects of extraversion and gender in mock jurors in attending to expert testimony were also examined. The dependent variables were the perceptions of the witnesses’ credibility and agreement with testimony and the participants were 210 psychology undergraduates. Likeability of expert witnesses was found to be significantly related to judgments of trustworthiness of the experts, but not related to confidence or knowledge of the experts or to the mock juror sentencing decisions. Women participants rated high likeable experts as more credible than low likeable experts; men did not. For men jurors, agreement with testimony increased as extraversion increased. However, for women jurors, agreement with testimony decreased as extraversion increased. The results suggest that likeability can be an important element of source credibility, and that attorneys and trial consultants now have an empirical foundation for addressing likeability as part of witness preparation.

The power of language in leadership positions and social movements is well established. Charismatic Language patterns have been identified as effective for influencing perception and decision-making. This study examines the use of Charismatic Language in a court of law through a randomized survey of different treatments of oral arguments in a homicide case. Results show that Charismatic Language used by the prosecution is less likely to influence a jury and can even dissuade their decision. Additionally, the study finds that Charismatic Language used by a female attorney may hinder the argument's reliability to a jury.