Time sequencing the TRAP-18 indicators.

A time sequence analysis is conducted on 125 lone actor terrorists, most of whom mounted attacks in Europe and North America, utilizing the TRAP-18 (Terrorist Radicalization Assessment Protocol), a structured professional judgment instrument with demonstrable interrater reliability and criterion, discriminant, and predictive validity. Both frequency filters (>3) and coefficient filters (>.50) were applied to the data. Results indicate that virtually all distal characteristics, such as criminal violence, mental disorder, and ideology, preceded the proximal warning behaviors, such as pathway, fixation, identification, leakage, last resort, and directly communicated threats. Indicators that were “gatekeepers” and “turning point events” were also identifie d (Taylor et al., 2008). The time sequence analysis further validates the model of the TRAP-18 as a risk instrument for the assessment and management of lone actor terrorist violence. This study applies a terrorist risk assessment instrument, the TRAP-18, to a large sample of lone actor terrorists using time sequence analysis: a method by which indicators of risk are organized in a temporal relationship with one another. It allows counterterrorism investigators to better understand the unfolding of risk indicators over time on the way to a terrorist attack, and helps prioritize the most dangerous cases.