The question of why jurors decide to acquit or convict the defendant in criminal trials has long intrigued researchers. Earlier studies found only weak ties between jurors' views of the case and juror demographics (gender, age, race), although some researchers noted a possible exception for the effect of race. The influence of jurors' attitudes/values is not well understood, but some researchers have suggested that opinions about capital punishment may affect jurors' votes in murder trials. There is consensus, however, that the strength of the evidence is a critical variable in jury verdicts. Researchers also generally agree that a jury's final vote is affected by the dynamics of deliberation and by the size of the initial majority (tally of the first votes).
Using data supplied by the National Center for State Courts, this study isolated the effects of juror demographics and attitudes and case characteristics on jurors' preliminary verdict preferences in criminal trials held in Los Angeles, CA, Maricopa County (Phoenix), AZ, Bronx, NY, and Washington, D.C. during the period June, 2000 to August, 2001. The demographic data included the age, gender, and race of the jurors and the race of the defendant; the attitudinal data concerned juror perceptions about the fairness of the law, the harshness of the consequences for the defendant, and the credibility of police testimony; the case characteristics centered on the presence or absence of a victim. Researchers controlled for the influence of the initial majority and the effect of deliberations on the final outcome by focusing on the first (pre-deliberation) vote. They controlled for the strength of the evidence by comparing jurors' assessment of the proof presented against that of the presiding judge; in fact, the study found that the judge's evaluation of the evidence was strongly associated with jurors' first vote.