A review of the literature indicates that young males, who are unemployed with low levels of education, predominate in populations of pre-trial criminal offenders suspected of having a psychiatric illness, also known as “Observation Patients” according to the Criminal Procedures Act of 1977 in South Africa. Other contributory factors include a history of mental illness and non-compliance on psychiatric medication, a previous forensic history, co-morbid substance abuse and being intoxicated at the time of the offence. Dual diagnosis is considered a key contributor to criminal behaviour in this group of patients. The review of the literature also shows a significant proportion of co-morbid intellectual disability among offenders found to be psychiatrically ill at the time of the criminal event. A previous study conducted 20 years earlier, in 1986 at the Sterkfontein Forensic Psychiatric Unit by Vorster (1986) showed that the typical profile was a single, unemployed, poorly educated male in his twenties, usually with a history of psychiatric treatment. This typical profile confirmed the evidence in the literatures at the time of the study.