Foreshadowing targeted violence: Assessing leakage of intent by public mass murderers

The idea that identifiable behaviors presage violence is a core concept in the threat assessment literature. Especially meaningful from an operational perspective is “leakage”, which concerns whether offenders intentionally or unintentionally reveal insights into their thoughts or feelings that suggest impending targeted violence. Previous research has generally been limited to assessing the prevalence of leakage in various offender populations. The present study more thoroughly describes leakage in a sample of 115 public mass murderers in the U.S. whose activities took place between 1990 and 2014. We disaggregate leakage into three distinct forms (written statements, verbal statements to the public, verbal statements to family/friends), and examine these in relation to theorized correlates of leakage. We found that a significant predictor of leakage is the presence of a grievance, specifically a grievance against a person or entity, as opposed to a grievance against a category of people or a grievance against an idea, movement or religion. We discuss implications of these results as well as directions for future research.