A follow-up survey was conducted to identify risk factors that influence recidivism. We analyzed the recidivism of 520 delinquents who were released from a Juvenile Classification Home. The analysis was performed by using split population model that was one technique of survival analysis. As a result, the following risk factors were revealed to be significant predictors of the recidivism, low age at commitment, low IQ score, property offense, the violation of the Road Traffic Law, robber and broken home. This paper clarified risk factors of delinquents released from a Juvenile Classification Home with the evidence by using a statistical model. An empirical research of risk factors of the recidivism is very few in Japan, so the technique used in this paper and the obtained findings are important. It will be thought that a more detailed, more objective risk assessment becomes possible, by accumulating variables and building findings.

Two main models, namely, Terri Moffitt's hypotheses and Travis Hirschi and Micheal Gottfredson's General Theory of Crime, have been proposed since around 1990, as an explanation of the consistency and change of individual criminality. There has been a heated debate over the relative validity of the two models. This research attempts to contribute to the solution of this debate. By defining criminality that gives rise to individual offending behavior as a probability process, the two models are expressed in a single framework. We examined whether the predictions of these two models better fit the actual observation obtained from the event history analysis of the recidivism of releasees from a Juvenile Classification Home. The result suggests that Moffitt's hypotheses are more congruent with the observation.