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Of 81,199 adult offenders, 26% reoffended within two years of the index appearance.
To re-examine the Group Risk Assessment Model (GRAM) for predicting reoffending in adults given non-custodial sentences and to assess the accuracy of the model.
Adult offenders given non-custodial sentences in 2011 were the cohort of interest. Reoffending within 24 months of the index appearance was measured using court data. Models predicting reoffending using personal, index offence and criminal history characteristics were undertaken using multivariate logistic regression and model fits were assessed. Model validity and reliability was also measured by applying the model estimates to sub-group data and to separate smaller cohorts.
Of the 81,199 adult offenders, 26% reoffended within two years of the index appearance. The best model fit for GRAM 2 comprised age, gender, Indigenous status, number of concurrent offences, prior custodial sentence, prior proven offences and the index offence type. The internal and external validity of the model was strong, however application of the model to offenders from smaller geographical areas or to those with a prior history of prison or property offending should be undertaken with care. Application of the model for screening purposes should also be carefully considered.
The GRAM 2 has been shown to be a robust tool for predicting reoffending. Although reliable, model estimates and their applicability should be re-examined periodically.