Whether and to what extent juvenile offenders specialize in commilling certain types of crimes during their delinquent careers has substantial impfo.:ations for theory and policy. The question of offender specialization arguably first emerged with the advent of the positivist school in crimi­nology in the late nineteenth century when Caesare Lombroso sought to identify criminal types. With the intrduction of specialized juve­nile justice in laws in the early twentieth century and their fundamental refomls in many countries in the second half of the twentieth century and into the initial decade of the twenty-first century, there have been considerable theorizing, research, and debate about specialization in youthful offending. Political debates in countries such as Australia, Canada, England-Wales, and the United States concerning the refonn of youth justice laws have been inHuenced, in part, by the considerable research on speciali1,a1ion youthful offending. The main theoretical debate ha<; been focused on the attempts 10 specify potential distinguishing charncteristics of certain types of violent juvenile delinquents such as serious sex­ual offenders, murderers, and gang members, compared to less serious violent offenders, prop­erty offenders, and drug users/traffickers, for example. Many diverse labels have been applied to young offenders, such as serial fire-seller/rap­ist/murderer, career criminal, life-course-persis­tent/adolescence-limited offender, chronic/ nonchronic offender, and adolescent psycho­path/conduct disordered, that typically include attempts to specify types and patterns of crime. Oftentimes these labels or categories have been introduced into the media, political, and legisla­tive circles, and debates emerge about whether to incarcerate, punish, and/or rehabilitate juvenile delinquents depending on what "type" of offender they are.