Expert Diagnostic Evidence By Psychologists: Disciplinary Tensions and Admissibility Issues

Controversy has existed since the 1960s on the difficult issue of the subject matter upon which psychologists should be permitted to offer expert opinions to the courts. A particularly problematic aspect of the controversy has been evidence by psychologists about diagnoses which generally is given by reference to the two main taxonomies of diagnosis, the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders and the World Health Organization's International Classification of Diseases. This column reviews the leading decisions on the issue in the United States, the United Kingdom and Australia, including a 2021 Queensland Court of Appeal decision. It argues that the trend of recent case law is in favour of psychologists being permitted to give such evidence but only, on a case-by-case basis, when sufficient specialised knowledge is established in relation to the specific diagnosis proposed by a psychologist.