“Experts” appear in the modern American courtroom on the jury as well as in the witness box, posing a dilemma for the legal system by offering a potentially valuable resource and an uncontrolled source of influence. Courts give ambiguous guidance to jurors on how they should handle their expertise in the deliberation room. On the one hand, jurors are told that they should “decide what the facts are from the evidence presented here in court.” By direct implication, then, jurors should not use outside information to evaluate the evidence. Jurors are also told, however, that they should “consider all of the evidence in the light of reason, common sense, and experience.” And indeed, all decision makers, including jurors, are unavoidably influenced by their own backgrounds and experiences as they evaluate evidence and reach decisions.

In this Article we examine the actual and desirable behavior during deliberations of jurors with specialized expertise. We draw on three sources to assess how often citizens with specialized knowledge serve as jurors, how they behave when they do, and how legal professionals view the appropriateness of the contributions juror-experts may make. Our sources include: (1) a survey of 167 experienced trial attorneys who reported on their recent trial experience with juror “experts”; (2) the actual deliberations of jurors in fifty civil trials from the Arizona Jury Project, which revealed how real jurors use their expertise in the jury room; and (3) a survey of 128 judges and attorneys who evaluated examples of “expert” juror behavior.

Some scholars suggest that jurors with specialized expertise should be excused for cause. In light of our findings, we conclude that such drastic intervention is unwarranted and would inappropriately undermine the increasing heterogeneity on the jury that the elimination of occupational exemptions has worked to promote. We instead advocate a tempered response to the growing presence of juror expertise in the jury room.