The text addresses procedures governing courtroom trials and introduces the major actors: jurors, defendants, and victims. It reviews three procedural issues attracting much research attention: the psychological consequences of employing an adversarial system of justice, the effects of the order of presenting information, and the comprehensibility and effectiveness of judicial instructions to jurors. A discussion of juror selection describes the fundamental principles, key issues, and involvement of psychologists in jury selection. One paper focuses on the effects of defendants' and victims' personal characteristics on trial outcomes. Two chapters examine the general issue of testimony, including the question of eyewitness reliability and witness credibility. Three chapters review research on the decisionmaking process for the individual juror, the jury, and the judge. The final section looks at methodological considerations in the study of courtroom psychology and the problem of innovation and change in the courtroom. Tables, footnotes, chapter references, and author and subject indexes are supplied. For individual papers, see NCJ 897672-71. (Author summary modified)