Suspicious preoperational activities and law enforcement interdiction of terrorist plots

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The purpose of this paper is to provide a metric for validating the Nationwide Suspicious Activity Reporting (SAR) Initiative’s (NSI) sixteen-category instrument, which is designed to guide law enforcement in the collection and analysis of suspicious behaviors preceding serious crimes, including terrorist attacks. Data on suspicious preoperational activities and terrorism incident outcomes in the USA between 1972 and 2013 come from the American Terrorism Study (ATS). Using a mixed-method approach, the authors conduct descriptive and multivariate analyses to examine the frequencies of the least and most prevalent suspicious activities (or SAR indicators) and how they predict the likelihood of terrorism prevention. In addition, the authors contextualize how configurations of SAR indicators are associated with the successful thwarting of terrorism incidents by law enforcement using an analytical method known as conjunctive analysis of case configurations (CACC).