Arrests and convictions but not sentence length deter terrorism in 28 European Union member states.

While countries differ in how they handle terrorism, criminal justice systems in Europe and elsewhere treat terrorism similar to other crime, with police, prosecutors, judges, courts and penal systems carrying out similar functions of investigations, apprehension, charging, convicting and overseeing punishments, respectively. We address a dearth of research on potential deterrent effects against terrorism by analysing data on terrorism offending, arrests, charges, convictions and sentencing over 16 years in 28 European Union member states. Applying both count and dynamic panel data models across multiple specifications, we find that increased probability of apprehension and punishment demonstrate an inverse relationship with terrorism offending, while the rate of charged individuals is associated with a small increase in terrorism. The results for sentence length are less clear but also indicate potential backlash effects. These findings unveil overlaps between crime and terrorism in terms of deterrent effects and have implications for both the research agenda and policy discussion.