Lone-actor terrorist attacks are on the rise in the Western world in terms of numbers and severity. Public officials are eager for an evidence-based tool to assess the risk that individuals pose for terroristic involvement. Yet actuarial models of risk validated for ordinary criminal violence are unsuitable to terrorism. Lone-actor terrorists vary dramatically in their socio-psychological profiles and the base rate of terrorism is too low for actuarial modeling to achieve statistical significance. This Article proposes a new conceptual model for the terroristic threat assessment of individuals. Unlike risk assessment that is founded upon numerical probabilities, this threat assessment considers possibilistic thinking and considers the often idiosyncratic ideologies and strategies of lone-actor terrorists.

The conceptual threat assessment model connects three overlapping foundations: (a) structured professional judgment concerning an individual’s goals, capabilities, and susceptibility to extremist thought, plus the imminence of a potential terroristic attack; (b) a multidisciplinary intelligence team engaging collective imaginaries of an otherwise unknown future of terrorism events; and (c) coordination between counterintelligence officials and academic communities to share data and conduct more research on lone-actor terrorists utilizing a systematic case study approach and engaging theoretical methodologies to inform about potential new ideological motivations and terroristic strategies which may be emerging due to cultural, environmental, and political drivers.