Exploring criminal specialisation in co-offending groups

Researchers have studied criminal specialisation at the offenders’ level to understand criminal careers. Despite criminal careers comprising events in which offenders co-offend with others, we know less about the extent of co-offending groups showing signs of becoming specialists. To start addressing this gap, in this study we report a method through which we identified 1,796 co-offending groups in a network containing information about adult offenders (n = 76,697) connected to criminal investigations (m = 35,604) between 2010 and 2018. During this timeframe, one in five co-offending groups remained unchanged in their composition and re-offended. Of those re-offending, 54% became specialists in crimes such as those affecting private property. The other 46% that re-offended were generalists. Simulation analyses showed that the proportion of highly specialised groups was not observed by chance. These results suggest that criminal specialisation is a characteristic also shared by co-offending groups. Criminologists and practitioners might find helpful the method employed here to identify co-offending groups and assess their level of specialisation.