Numerous research studies in Australian and other Western nations have reported that persons with an intellectual disability are over-represented in prison populations when compared with the prevalence of intellectual disability in the general community. The question remains whether the over-representation in prisons reflects an over-representation of persons with an intellectual disability appearing before courts, or whether they receive differential treatment by the criminal justice system, resulting in a greater proportion of intellectual disabled accused persons receiving custodial sentences.
This study aimed to investigate the specific question of whether persons with an intellectual disability are over-represented in the population of people appearing before the criminal courts. The results show that lawyers and magistrates may find that one in four of the people appearing before Local Courts have intellectual deficits (including difficulties in verbal skills, memory, reasoning and understanding) which make it extremely difficult for them to participate adequately in the process of justice, and that nearly one in three of the people appearing had results indicating further expert assessment of mental state may be appropriate.
The study took place in four Local Courts in New South Wales - Liverpool, Wagg Wagga, Dubbo and Newtown Local courts were selected for the study because of the high-flow through rate of court appearances, and the range and diversity of offences. Most minor offences are disposed of at this level, and serious criminal offences also initially come before Local Courts for committal proceedings. The particular four courts were selected because they draw from varied socio-economic and ethnic populations. People aged 18 years or older appearing before the Local Courts during seven working days in September-October 1992 were asked to participate voluntarily in the study. These persons completed a form which sought demographic and background information; the Matrices section of the Kaufman Brief Intelligence Test (K-BIT); and an abbreviated version of the Mini-Mental State Examination (MSE). The researchers noted any obvious difficulties or abnormalities.
A total of 120 persons participated in the study, although complete data sets were not obtained from all participants. The sample was not significantly different form the total population presenting to New South Wales Local Courts in respect to category of offence(s), or proportion who had legal representation. Although somewhat under-representative of Aborigines and Islanders, the sample was considered to be sufficiently representative of the New South Wales Local Courts population to allow some conclusions to be drawn.
The K-BIT results show that 14.2% of the sample had a standard score of less than 70, placing them in the mildly intellectually disabled range of cognitive ability. A further 8.8% were in the borderline category. Twenty-five percent of the sample were at or below a percentile rank of 10, indicating that 90% of the population are functioning better than these participants in the area of cognitive skills.
The research also revealed that 31% of those completed the mental state section of the survey fell below the cut-off score which indicates that a further assessment of mental state should be undertaken. An overall total of 36 participants (30% of the sample) had results on one or both tests which would probably have serious difficulty in comprehending or coping with court procedures, and may need further expert assessment.
The study identifies a very important need for identifying the presence of mental abnormality, particularly intellectual disability, in persons appearing before Local Courts. Further research is indicated to extend the scope of the sample, to assess the population appearing before higher courts, and to evaluate possible procedures for identifying the accused with a mental impairment.
