Networks of criminal offenders have received a lot of attention during recent years. This is due to the rising share of crime that these networks account for and to recent, network-based crime fighting strategies that have been pursued in many countries with widelyvarying degrees of success.

The aim of this research project is to study how targeting criminals embedded in some network can have important effects on crime reduction. To do this, we will address two important questions concerning the role of social interactions and social networks in the etiology of crime. First, we want to investigate the role of peer effects in crime. Second, we want to test the empirical relevance of the "key player" policy in an important, real world setting, where the aim is to target the criminal who once removed from the network reduces total crime the most. We also want to compare the predictive performance of the key player policy to the performance of other policies based on more traditional measure of network centrality and to other reasonable policies such as targeting the most
active criminals.

Following this, we intend to investigate the origins co-offending networks. We will study the importance of family, neighborhood, and school-level networks for the formation of juvenile delinquent networks. We will also study the effect of juvenile detention and adult incarceration on changes in the strength and structure of co-offending networks (post release).