Students playing the roles of jurors judged cases involving fellow-students charged with disciplinary offenses under the student code (i.e., theft of an examination, assault and battery, unauthorized use of a faculty account, and possession of marijuana), both by rendering a guilty or not-guilty verdict and stating their reactions to the credibility of prosecution and defendant, based on the subjects' prior knowledge that the defendant had, or did not have, a prior conviction. Contrary to the working hypotheses upon which the experiments were based, the presence or absence of a prior conviction did not have a significant effect on either the defendant's credibility or the verdict. However, for those jurors who found the defendant guilty, a more severe punishment was imposed on the defendant if he had a prior disciplinary offense than if he had no prior disciplinary record. Seventeen appendixes form the main body of this study. The text contains no footnotes. A bibliography containing 31 references is appended.