Prevalence of intellectually handicapped offenders serving custodial and non-custodial sentences

Criminology Research Council grant ; (6/87)

This project sought to assess the incidence of intellectual disability in New South Wales prisons. Five gaols were selected, and prisoners were administered a screening test. Those scoring below a pre-determined cut-off point on the screening test were given a full assessment which included the Wechsler Adult Intelligence Scale, the Ravens Progressive Matrices (Standard and/or Coloured), and the Vineland Adaptive Behaviour Scale. Using a definition of intellectual disability which incorporated both cognitive and adaptive behaviour deficits, all the data point to an incidence of 12-13 per cent with IQ less than 79, approximately 4 per cent greater than the proportion of intellectually disabled people in the general population. Particularly low levels of functioning were found in the communication sub-domain of the Vineland Scale. Results indicate that intellectually disabled prisoners are found at all security classification levels from minimum to maximum, and have committed offences ranging in severity from mild to serious, including assault and murder.

Aboriginal prisoners were greatly over-represented amongst the intellectually disabled group. In addition, their communication and socialisation were significantly lower than non- Aboriginal Australians.

Participation in the study was not compulsory. Participation rates varied amongst gaols from a low of 45 per cent at Parramatta to a high of 100 per cent at Broken Hill. For these reasons the figure of one in eight prisoners with an intellectual disability must be seen as a base line estimate.

The study has important implications for the management of intellectually disabled prisoners, with the desirability of unit living with opportunities for acquiring social and adaptive skills being highlighted. The need for training of custodial and non-custodial staff is of paramount importance, given that many of the intellectually disabled prisoners are functioning at levels of lower than seven years of age. There are also implications for the availability and design of educational programs to enhance social, relationship, communication and daily living skills so that intellectually disabled prisoners can have the opportunity for independence and a non-criminal lifestyle in the community.