Limitations in the Prediction of Mass Violence: Cautionary Tales.

The incidents of mass violence that have occurred in the United States have been deeply disturbing to the public as well as to mental health professionals. The public, the media, as well as our patients, family members, and friends have reached out to mental health professionals in the hope that we can provide an understanding of these events that might serve to reduce their frequency in the future. This article explores how we can best respond to these requests, including the current limitations of psychologists in the prediction of mass violence. Two incidents of mass violence are used to illustrate these issues. The first is a review of the investigation of the explosion on the U.S.S. Iowa in April 1989 that resulted in the deaths of 47 seamen. The second incident used for illustration purposes will be the University of Texas Clock Tower shootings that occurred in August 1968. This article discusses the reliability and validity problems inherent in retrospective reviews of the personality characteristics of perpetrators, and the limitations imposed by base-rate issues in the prediction of mass violence.