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    Support for this research was provided by Grant N00140510629 from the Department of Homeland Security through the National Consortium for the Study of Terrorism and Responses to Terrorism (START). Any opinions, findings, conclusions, or recommendations in this document are those of the authors and do not necessarily reflect the views of the Department of Homeland Security. An earlier version of this article was presented at the Stockholm Criminology Symposium, Stockholm, Sweden, in June 2006. We would like to thank Karen Heimer, Clark McCauley, Brendan O'Leary, Jean McGloin, Peter R. Neumann, Allison Smith, Bert Useem, Robert W. White, and several anonymous reviewers for their helpful comments on earlier drafts, as well as Hugh Barber, Susan Fahey, and Erin Miller for their assistance with the database. Direct correspondence to Gary LaFree, START Center, University of Maryland, 3300 Symons Hall, College Park, MD 20742 (e-mail:, and to Laura Dugan, Department of Criminology and Criminal Justice, University of Maryland, 2220 LeFrak Hall, College Park, MD 20742 (e-mail:


Since philosophers Beccaria and Bentham, criminologists have been concerned with predicting how governmental attempts to maintain lawful behavior affect subsequent rates of criminal violence. In this article, we build on prior research to argue that governmental responses to a specific form of criminal violence—terrorism—may produce both a positive deterrence effect (i.e., reducing future incidence of prohibited behavior) and a negative backlash effect (i.e., increasing future incidence of prohibited behavior). Deterrence-based models have long dominated both criminal justice and counterterrorist policies on responding to violence. The models maintain that an individual's prohibited behavior can be altered by the threat and imposition of punishment. Backlash models are more theoretically scattered but receive mixed support from several sources, which include research on counterterrorism; the criminology literature on labeling, legitimacy, and defiance; and the psychological literature on social power and decision making. In this article, we identify six major British strategies aimed at reducing political violence in Northern Ireland from 1969 to 1992 and then use a Cox proportional hazard model to estimate the impact of these interventions on the risk of new attacks. In general, we find the strongest support for backlash models. The only support for deterrence models was a military surge called Operation Motorman, which was followed by significant declines in the risk of new attacks. The results underscore the importance of considering the possibility that antiterrorist interventions might both increase and decrease subsequent violence.