Normal Science and Middle-Range Theory in Criminology: Assessing the Contested Notion of Offending Specialization

This review traces the evolution of the specialization concept in criminology and assesses its value for theory, research, and policy. Although empirical research has generally shown that most offenders exhibit versatility rather than long-term specialization, we argue that specialization remains an important dimension of criminal behavior and is productive for middle-range theory and normal science in criminology. We assess common methodological approaches to measuring specialization, highlighting how differences in operationalization shape substantive conclusions. We then synthesize contemporary research that uses specialization to probe theoretical mechanisms, examine social and developmental processes, and evaluate justice system practices and policy. Across these areas, between- and within-individual variation in specialization (versatility) informs questions about opportunity, peer influence, decision-making, and the criminal career. We conclude that specialization should not be treated as a binary property but as a conditional, theoretically generative construct that, if effectively utilized, can advance criminology's objectives.