Predictive validity of the START with intellectually disabled offenders

Abstract

Purpose – Offenders with intellectual disability (ID) have been largely neglected in past forensic literature on assessment of dynamic risk factors. The purpose of this paper is to evaluate the predictive validity of the Short-Term Assessment of Risk and Treatability (START), in a sample of males with IDs in a low-secure hospital (n=28). Design/methodology/approach – A prospective analysis was conducted, with START scores as the predictor variables, and the number of recorded aversive incidents as the outcome measure. Findings – Receiver operating characteristic analysis demonstrated that total START risk scores had a significant high predictive accuracy for incidents of physical aggression to others (area under the curve (AUC)=0.710, p<0.001) and property damage/theft (AUC=0.730, p<0.001), over a 30-day period, reducing to medium predictive validity over a 90-day period. Medium predictive validity was also identified for incidents of verbal aggression, suicide, self-harm, and stalking and intimidation. START strength scores were also predictive of overt aggression (AUC=0.716), possible reasons for this are explored. Research limitations/implications – The small sample size limits the generalisability of the findings, and further research is required. Practical implications – The paper offers preliminary support for the use of the START with ID offenders in low-secure settings. Given the lack of validation of any previous dynamic risk assessment tools, multi-disciplinary teams in such settings now have the option to use a tool which has potentially good validity with an ID population. Originality/value – This study represents the first attempt to examine the predictive validity of the START with ID offenders, and a step forward in the understanding of dynamic risk factors for violence in this population. The significant predictive relationship with incidents of physical aggression and property damage offers clinicians a preliminary evidence base supporting its use in low-secure settings.