Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Psychology (PhD)

Degree Level



Psychological Science


James M. Lampinen

Committee Member

David A. Schroeder

Second Committee Member

Scott Eidelman


Social sciences, Psychology, Attribution theory, Criminal trails, Decision making, Excuse defense, Juries


In the typical criminal trial, a defendant is trying to prove he/she is not guilty because they were not the individual that committed the crime. However, another type of defense exists in which the defendant admits they were the culprit, but provides an excuse in an attempt to avoid criminal punishment. These so called "excuse defenses" include insanity, involuntary intoxication, age, and entrapment. In all cases, juries are required to determine whether the defendant had sufficient mental capacity to form the intent to commit the crime. Although jury decision making is a popular research area in psychology, relatively little has been done to examine excuse defenses. In the following paper, three theoretical areas were discussed in relation to excuse defenses: excuses in interpersonal relationships, the traditional jury decision making Story Model, and Social Attribution Theory. A combined theory designed to specifically explain jury decision making in excuse defense cases was postulated and two experiments were performed to test this theory. In Experiment 1, participants read a trial summary in which the type of excuse defense and aspects of Attribution Theory were varied. Experiment 1 found weak support for the importance of Attribution Theory in jury decision making. The strongest predictor of participants' verdicts was the Crime Control versus Due Process Orientation. Conclusions based on Experiment 1 should be limited however due to a significant number of participant problems. Experiment 2 utilized a card selection task in which participants chose which evidence they wished to view. Experiment 2 found strong support that Attribution Theory plays an important part in jury decision making and that the importance of evidence changes depending on the type of excuse defense used. For Entrapment, Consensus and Distinctiveness are both important, however, for Brain Damage, Distinctiveness evidence takes priority. The proposed theory was discussed with regard to the evidence provided in the current experiments and implications for individuals working in the legal system were suggested.