The principle that perpetrators of atrocity should be brought to justice before courts of criminal law enjoys near total acceptance. However, because of the nature of the transgressions adjudicated, the major trials of perpetrators have also served a didactic and moral function in redefining and re-imposing rule-based legality. As a consequence, these trials address history and memory in the course of trying the accused. This essay examines three particular filters that affect the way the memory and history of the events concerned enter the trial process: first, the nature of the evidence admitted; second, the substantive incriminations directed at the accused; and third, the principle of criminal accountability deployed by the prosecution. The essay also considers how the timing and place of the trial influence its didactic value. Ultimately, the didactic and moral effectiveness of such trials is beyond the control of the courts and can only be evaluated over the longer term.