By Gary LaFree , · Bo Jiang and· Lauren C. Porter

Abstract Objectives In the current study we consider the link between imprisonment and post-prison participation in violent political extremism. We examine three research questions: (1) whether spending time in prison increases the post-release risk of engaging in violent acts; (2) whether political extremists who were radicalized in prison are more likely to commit violent acts than political extremists radicalized elsewhere; and (3) whether individuals who were in prison and radicalized there were more likely to engage in post-prison violent extremism compared to individuals who were in prison and did not radicalize there. Methods We perform a two-stage analysis where we frst preprocess the data using a matching technique to approximate a fully blocked experimental design. Using the matched data, we then calculate the conditional odds ratio for engaging in violent extremism and estimate average treatment efects (ATE) of our outcomes of interest. Results Our results show that the efects of imprisonment and prison radicalization increases post-prison violent extremism by 78–187% for the logistic regression analysis, and 24.6–48.53% for the ATE analysis. Both analyses show that when radicalization occurs in the context of prison, the criminogenic efect of imprisonment is doubled. Conclusions In support of longstanding arguments that prison plays a major role in the identity and behavior of individuals after their release, we fnd consistent evidence that the post-prison use of politically motivated violence can be estimated in part by whether perpetrators spent time in prison and whether they were radicalized there.

Journal of Quantitative Criminology, (2020) 36:473–498