The rules of evidence that have evolved prevent lawyers from using the most powerful, yet the most informationally empty, techniques of persuasion. The rules compel litigators to fight their battles by presenting juries with information. Studies conducted on jury decision-making indicate that evidence—factual information about the events in dispute—is the most potent force driving the verdicts of trials. Studies show that judges and jurors would reach the same verdicts in four-fifths of trials; that similarity is because they are responding to the same information. Studies of differences among jurors in demographics, attitudes, personalities, and knowledge have found that in the great majority of cases such differences matter very little to the outcomes of cases. Variation in the strength of evidence influences decisions far more than who is hearing the evidence. That is good news if we want trials to produce rational decisions based on evidence. The focus on evidence makes a juror’s job a demanding one, presenting challenges to understanding, remembering, evaluating, drawing inferences, and using evidence (in conjunction with the law) to reach conclusions about a disputed matter. Working as a group helps. Groups have advantages over individuals: they possess more cognitive and social resources such as wider background knowledge and experience, the ability of multiple minds to remember, to correct each other’s errors, to think about the proper meaning of the evidence, and so on.
The Two–dimensional Model of Jury Decision Making