Research to date suggests that violent individuals with psychosis do not constitute a homogenous group, and subtypes of offender exist. One proposed subtype consists of people with comorbid antisocial personality traits, who constitute a significant proportion of individuals in forensic psychiatric services but have attracted little focussed research. This thesis aimed to characterise this comorbid group by examining the neuropsychological characteristics, emotion processing characteristics and clinical outcomes of male patients recruited from high-secure forensic psychiatric hospital, falling into one of the following diagnostic groups: 1. psychotic disorder (n=15); 2. dissocial personality disorder (DPD; n=17); and 3. comorbid psychosis and DPD (n=26). Clinical groups were compared to each other and to a group of healthy controls (n=30) on measures of neuropsychological functioning, facial affect recognition, sensorimotor gating and appetitive and defensive responding. In addition, the clinical groups were compared on their historical characteristics (offending, psychosocial, psychopathy) and current clinical outcomes, corresponding to clinician rated clinical progress, risk/violence and engagement with the clinical team. The relationship between the characterisation measures and outcomes (progress, risk and engagement) was explored to assess the clinical relevance of such indices. The results supported a distinct subgroup of those with comorbid psychosis and DPD, who were characterised by a poorer sensorimotor gating profile and poorer fearful facial affect recognition than their non-DPD counterparts, with a tendency towards poorer neurocognition. The comorbid group was more similar to the DPD alone group on experimental and historical measures. The clinical groups did not differ from each other, or healthy controls, on appetitive/defensive responding, and the clinical groups did not differ with respect to outcomes. Measures of memory, executive function and facial affect recognition correlated with indices of outcome, suggesting that such characteristics may be promising treatment targets within forensic mental health services.