Experimental Research on Jury Decision-Making

Abstract

Because trial juries deliberate in secrecy, legal debates about jury functioning have relied heavily on anecdote and speculation. In recent years, investigators have begun to challenge many common assumptions about jury behavior. An important tool in this effort has been the mock jury experiment, in which research participants are randomly assigned to alternative trial conditions and asked to reach a verdict in a simulated case. Researchers have used mock jury experiments to test hypotheses about causal influences on jury behavior and to develop theoretical models of the jury deliberation process.

Issues in data monitoring and interim analysis of trials

“…These different decision rules usually result in the same verdict in mock jury experiments. 140,167,168 Some studies show that a unanimous decision rule results in 'hung juries' more often than a majority decision rule. Juries operating under a unanimity rule deliberate for longer and spend more time discussing legal definitions of verdict categories.…”

“…A large number of such factors has been studied and reviewed. 140,145,167,168 From these, 12 have been shown to have sizeable effects on jury decision outcomes: definitions of key legal terms, verdict/sentence options, trial structure, juror-defendant demographic similarity, jury personality composition, jury attitude composition, defendant criminal history, strength of evidence, pretrial publicity, inadmissible evidence, case type (for civil trials) and initial juror verdict preference distribution. Some topics not included in this list are associated with small yet reliable effects (e.g.…”

“…Following this decision, federal government and most states banned access to the jury room, limiting the range of research that could be conducted with real juries. 140,167 Since that time, research on jury decision-making has largely been confined to experimental studies of mock juries, interviews or surveys of real jurors after their deliberations and archival studies of real jury verdicts. In the 1990s, two large field studies of juries were initiated in the USA.…”

“…140,165 Smaller juries are less likely to include members of minority groups, recall less evidence, deliberate more quickly and less thoroughly, and less likely to reach a verdict. 140,167,168 Six-member juries award larger damages in civil cases. 140,168 Decision rule Juries may be asked to return a verdict on the basis of either a unanimous or a majority decision (usually a two-thirds majority).…”

Do Judges Vary in Their Treatment of Race?

“…3 "No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws." Amendment XIV, US Constitution 4 Given this difficulty, a number of studies (Devine, et al, 2000;Sommers and Ellsworth, 2000;MacCoun, 1989) have made use of experimental simulations of court cases, most often to understand the behavior of juries. While laboratory studies allow the careful manipulation of the variable of interest, defendant race, sectional studies suffer from a potentially severe omitted variables bias.…”