Criminal and drug use careers : a trajectory-based analysis of the path-dependent and age-graded relationship between drug use and crime

Abstract

For criminology in Australia, 2012/13 will likely be remembered with cautious concern. It was a period of significant change, bringing with it a number of policy decisions which, together, forewarn of a difficult and challenging period ahead. Above all, as the jurisdiction in which this thesis makes its journey, Queensland will be remembered as the first in Australia to have terminated its multi-agency court-supervised drug treatment program, significantly limiting the sentencing options available to those most in need of alternatives to imprisonment. Looking ahead, the future is set to be equally challenging as the paucity of Australian longitudinal and developmental criminological research stands as a significant obstacle in the search for new and proven alternatives. Against this backdrop, this thesis returns to the Queensland component of the Australian Institute of Criminology's (AIC) Drug Use Careers of Offenders (DUCO) study to consider the policy implications of a path-dependent and age-graded relationship between drug use and crime. Using previously unanalysed conviction history data for a representative sample of 1,184 Queensland prisoners, this thesis employs Group Based Trajectory Modelling (GBTM) to identify six quantitatively distinct conviction trajectories spanning the 20 year period between ages 10 and 29, inclusive. Of the six trajectories identified, none exhibited the hallmark characteristics of a life-course persistent offender profile. Instead, a trajectory of high-rate chronic offenders was identified and whose trajectory evinced a clear pathway to desistance as their exposure-adjusted rate of conviction declined steadily throughout their late 20s. In addition, an early-onset trajectory was identified sharing features consistent with that generally described as 'adolescent-limited', while a sample of 'late-bloomers' was identified bearing the hallmark features of an adult-onset and late-peaking conviction trajectory. Once extracted, the six conviction trajectories were later used to examine a series of self-reported illicit drug use indicators, including lifetime prevalence, the trajectories and sequencing of drug use initiation, and the age and speed of escalation to regular and dependent use. Further, measured as a time-varying covariate the initiation of regular illicit drug use was incorporated into the GBTM model to explore path-dependent and age-graded relationships. The results confirmed that although the lifetime experience of drug use was remarkably similar between offenders of different trajectories, the correlation between drug use and conviction rates was both path-dependent and highly variable within trajectories at different stages of the life-course. The theoretical and policy implications of these results are discussed, with a specific focus on the need for trajectory and age-specific interventions for high-rate, adolescent-limited and late-blooming offenders. Show more