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Suspicious preoperational activities and law enforcement interdiction of terrorist plots

Jeff Gruenewald (School of Public and Environmental Affairs, Indiana University Purdue University at Indianapolis, Indianapolis, Indiana, USA)
Brent R. Klein (Michigan State University, East Lansing, Michigan, USA)
Grant Drawve (University of Arkansas, Fayetteville, Arkansas, USA)
Brent L. Smith (University of Arkansas, Fayetteville, Arkansas, USA)
Katie Ratcliff (University of Arkansas, Fayetteville, Arkansas, USA)

Policing: An International Journal

ISSN: 1363-951X

Article publication date: 6 November 2018

Issue publication date: 4 February 2019




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).


The study reveals several key findings. First, certain behaviors categorized as suspicious, such as making threats, occur more frequently than others. Second, making threats, conducting surveillance and terrorist recruitment/financing predict law enforcement interdiction in terrorism plots, while misrepresentation (or the manufacturing and use of false documents) is more associated with terrorist success. Third, prevalent SAR indicators operate differently in the context of various combinations of suspicious activities to shape the likelihood for law enforcement interdiction.

Research limitations/implications

The current study’s findings may not be generalizable to other forms of violent extremism and terrorism outside of the USA.

Practical implications

This study illuminates opportunities for the NSI to provide law enforcement with the necessary tools to reduce terrorism risk and prevent future attacks.


To our knowledge, no scholarly work to date has assessed how observable behavioral indicators of suspicious preoperational activities affect the outcomes of terrorist plots.



Gruenewald, J., Klein, B.R., Drawve, G., Smith, B.L. and Ratcliff, K. (2019), "Suspicious preoperational activities and law enforcement interdiction of terrorist plots", Policing: An International Journal, Vol. 42 No. 1, pp. 89-107.



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