Not So Different After All: Increased arrests and convictions (but not sentence length) deter terrorism

Michael Wolfowicz, Gian Maria Campedelli, Amber Seaward and Paul Gill

While countries differ significantly in how they handle terrorism, in the west, criminal justice systems tend to treat terrorism similar to other crime, with police, prosecutors, judges and courts, and penal systems carrying out similar functions of investigations, apprehension, charging, convicting, and overseeing punishments respectively. While there is a robust literature on deterrent effects for crime, there is a dearth of research when it comes to terrorism. This despite evidence of significant overlaps between crime and terrorism. We address this gap in the literature with a unique dataset covering terrorism offending, arrests, charges, convictions, and sentencing over 16 years in 28 EU-member states. Applying a dynamic panel data model, we find that the probability of apprehension and punishment has an inverse relationship with terrorism offending. Conversely, the rate of charged individuals is associated with a small increase in the terrorism offending rate. The results for sentence length are less clear, with either negligible, or small iatrogenic effects. The results demonstrate that the overlap between crime and terrorism may extend to general deterrence. These findings should be informative for both the research agenda and policy discussion.

PREPRINT - 2023. 16p.