The probabilities of sex offender re-arrest

Estimates of the probabilities of re-arrest for sex offenders apprehended in Western Australia between April 1984 and December 1994 are reported.

Of the 116,151 distinct male persons arrested for the first time from 1984 94, 2785 were identified with at least one sex offence. Subjects on average were followed up for 5.7 years and assessed by criminal record, Aboriginality, bail status, age, occupation and penal intervention. Three criteria, rearrest for any, repeat sex or a violent offence are used to summarize the 'careers' of sex offenders.

Overall ultimate probabilities of rearrest for any offence were 0.61, for a repeat sex offence 0.33 and for a violent offence 0.51. Probabilities of re-arrest for non-Aboriginal offenders were lower for all definitions. Younger offenders, Aborigines and those with prior arrest for non-sex offences had higher probabilities for any or violent rearrest but older offenders tended to have higher probabilities of repeat sex offending. Community supervision and imprisonment significantly reduced the 'rate' or speed of re-arrest.

Actuarial risk assessments for low-probability high-consequence events such as dangerous recidivism are useful for identifying groups with a high probability of rearrest, assisting management of these groups and evaluating penal interventions.