The examples of empirical phenomena are drawn from a research program on the highly conventionalized jury decisionmaking task. An analog of the actual jury decision task was created under the control of the experimenters. Sixty-nine 12-person juries were shown the same videotaped murder trial with 4 verdict alternatives. The first phenomena that was apparent in mock-jury research was that when many juries decide the same case they do not usually all render the same verdict due to individual differences in opinion among the jurors at the start of deliberation. A second generalization is that the larger a group advocating a point of view, the more likely the group is to persuade others to accept that point of view. A third phenomena involves shifts in individual opinion from the beginning to the end of deliberation that are not simply shifts toward the initial modal verdict preferences. A fourth phenomena involves the effects of an implicit or explicit agenda on the decision process and outcome. 55 references, 1 table, and 5 figures.