The six basic rules of jury deliberation are the jury is the finder of fact, the judge is the law giver, only evidence presented in court is to be considered, the jury must arrive at a unanimous decision (or near unanimous in civil cases), there are no time limits on deliberation, the juror must vote his conscience, and the evidence should be debated. The theoretical impact of these rules on group processes was examined through evaluation of videotapes of the deliberations of a jury which served at an experimental trial conducted in the Moot Courtroom of the State University of New York at Buffalo Law School. The study showed that the judge's instructions to the jury and the charge have important effects on the development of the jury as a group and on constraining and participation of individual members. The charge focuses the question and defines the jury's work. The rule that jurors consider only the evidence presented in court is powerful in restraining individual expressions of opinion. In building the group culture, jury members admonish each other to hold to the rules. Whenever a juror wishes to express an opinion, it must be referred back to the evidence, and others disagree if a juror misstates the testimony. A culture develops in which members internalize the rules. If the evidence is not there, the juror is unable to present a persuasive case to others. Thus, a fair trial outcome could be ensured by carefully socializing jurors to their roles and helping them to understand the rules of deliberation. Four tables, 2 figures, 9 footnotes, and 34 references are provided.