People with an intellectual disability in the criminal justice system: Developing an assessment tool for measuring prevalence

Objectives. To develop a screening tool to detect those who may have intellectual disabilities or borderline intellectual disabilities in the criminal justice system (CJS). Design. The items for the assessment tool were based on data from an earlier study. The assessment tool was piloted on 80 participants, who also completed a short form of the WAIS-R. Method. Items for the screening tool were derived using a discriminant analysis procedure with data from a previous study (measuring IQ and other factors in people on probation). A sample of 40 participants with an intellectual disability and 40 with an IQ in the normal range then completed the screening measure and the WAIS-R. Results. The screening measure showed good concurrent validity, and correctly classified 87% of participants. Conclusions. The screening measure is a useful tool for people working in the CJS to use in the identification of those who may be in need of further support owing to an intellectual disability or borderline intellectual disability.