The inﬂ uence of cognitive impairment is pervasive in all aspects of the care of mentally disordered offenders (MDOs). Substantial evidence now exists that the most common diagnoses among our clients, including schizophrenia, antisocial personality disorder (ASPD) and psychopathy, are associated with speciﬁ c cognitive deﬁ cits (e.g., Blair, 2003; Dolan and Park, 2002; Nuechterlein, et al., 2004). These deﬁ cits are compounded by their increased risk of acquired brain injury as a result of violence and substance abuse. In a cohort study of 256 special hospital patients, 91 per cent had either a diagnosis of schizophrenia or learning disability, a neurological injury or illness, or a history of drug and alcohol abuse indicative of probable impairment (O’Rourke and Hartley, 2011). Amongst a group of 125 special hospital patients, 79 per cent had one or more Wechsler Adult Intelligence Scale 3rd Edition (WAIS-III) IQ or index scores in the borderline range or below (O’Rourke and Hartley, 2011).