Juries have the implicit power to acquit defendants despite evidence and judicial instructions to the contrary. The jury's right to decide a criminal case by its own lights without fear of outside coercion and pressure has been a hallmark of Anglo-American jurisprudence. To some observers of criminal cases where juries nullified the evidence or instructions, jury acquittals in the face of ostensibly strong prosecution cases were tantamount to racially-based jury nullification. Others suggest that it is both possible and perhaps even probable that such acquittals were really not jury nullifications of the law, but simply instances of the prosecution failing to meet its burden of proof. This research tests a model of jury nullification and involves four experiments that examine the influence of judicial instructions and various fact and legal situations that may provoke juries to nullify. The mock jury experiments, as guided by the model, involve 1316 juror-participants using videotaped trials presented in a realistic setting. The first experiment is an exploration of the effects of jurors' emotional biases in reaching a nullification verdict. Jurors will view a trial that has elicited nullification verdicts or a trial that has not. Jurors will either be given standard (pattern) or nullification instructions by the trial judge. Emotional biases will be primed by varying the attributes of the victim who will be presented either in a neutral light or will be very unsympathetic. A second battery of experiments will delineate three nullification-relevant legal situations (i.e., unfair laws, unfair application of law to the defendant, and violation of due process). While commentators have argued that these situations tend to evoke the jury's nullification tendencies, there is no extant empirical evidence that this is so. The studies also investigate the impact of providing juries with nullification instructions as compared to standard (pattern) judicial instructions. The researchers examine the impact of these instructions on both the verdicts and dynamics of jury deliberations within the context of the three categories of nullification. The third proposed experiment explores the impact on a nullification decision of a juror who argues that the jury should focus on a just outcome rather than solely on an outcome that complies with the law (a trigger). The researchers experimentally manipulate the presence or absence of a trigger in two trials and analyze the effects on the jury's deliberations and verdicts. The research proposed will provide empirical evidence as to when, why, and how juries nullify and inform the debate as to whether juries should be informed of their power.