The majority of adolescents in contemporary developed nations engage in juvenile delinquency. But why do most delinquents desist whereas a few become violent career criminals. Moffitt's developmental taxonomy proposes that antisocial acts are committed by two very different 'groups' of people: A 'life-course persistent' group whose antisocial behavior onsets early in life and who become life-long offenders versus a larger 'adolescence-limited' group who offend during their teenage years, mostly reforming when they become adults with jobs and families. The theory contains numerous testable propositions. It has had wide-ranging impact, contributing to new methods for the study of longitudinal data and shaping discourse about the social construction of crime, psychiatric nosologies, crime and punishment, and legal rights and responsibilities.