Controversies in assessing risk and deviancy in sex offenders with intellectual disabilities

Abstract

While the literature on the assessment, treatment and management of non-intellectual disabled sex offenders is well established, it is only in recent years that researchers and clinicians have focused on sex offenders with intellectual disability (ID). This article focuses on two areas: the assessment of risk and recidivism, and the assessment of sexual deviancy in sex offenders with ID. The first part of this article reviews the literature on the assessment of sexual offence recidivism risk for sex offenders with ID. Static and dynamic risk factors associated with sexual recidivism risk in sex offenders with ID are identified and the use of actuarial risk assessment scales and structured risk assessment systems with this client group are considered. The second part of this article discusses difficulties associated with the assessment of sexual deviancy in sex offenders with ID. An alternative approach to assessing deviancy is considered where deviant behaviour is compared against a four-group continuum of normal to deviant sexual behaviour in terms of developmental and chronological levels. From the literature a number of suggestions are made regarding the assessment of risk and sexual deviancy with this client group.

Keywords:

• actuarial risk assessment
• sex offenders with intellectual disability
• static and dynamic risk

Acknowledgements

The author is grateful to the two anonymous reviewers for their helpful comments in revising this manuscript.

Notes

1. When considering the predictive accuracy of an actuarial risk scale, statistics derived from the ‘Receiver Operating Characteristic’ (ROC) analysis are preferred indices of predictive accuracy and effect size (Harris, 2003; Swets, Dawes, & Monahan, 2000). The ROC analysis plots the sensitivity against 1 – specificity, producing a line of data points across the graph. The ‘curve’ for a perfect test would travel up the vertical axis then along the top of the box until it reaches the top right-hand corner, producing a curve on the graph. A perfectly accurate test would yield an ‘Area under the Curve’ (AUC) of 1.0 (no overlap between recidivists and non-recidivists). In contrast, a diagonal line with an AUC of 0.50 indicates a test with a predictive accuracy no better than flipping a coin. The AUC statistic can be interpreted as the probability that a randomly selected recidivist would have a more deviant score than a randomly selected non-recidivist. A typical AUC for sexual reconviction is often in the range of about 0.75 (see Craig, Browne, & Beech, 2008).