Psychiatric and Clinical Characteristics of Offenders with Diminished Criminal Responsibility: A Scoping Review

Introduction: Diminished criminal responsibility represents an intermediate determination between full and absent criminal responsibility. This scoping review aimed to map the psychiatric and clinical characteristics of offenders with diminished criminal responsibility. Methods: PubMed/MEDLINE and Scopus were searched for English-language empirical studies published from 2010 up to the date of the literature search (4 September 2026), following Joanna Briggs Institute guidance and PRISMA-ScR. The searches identified 621 records; after removal of 182 duplicates, 439 unique records were screened. Eight eligible studies were identified through database searching and one additional study through supplementary citation searching, resulting in nine included studies. Results: The nine studies represented six jurisdictions and showed substantial heterogeneity in populations, legal definitions, and clinical characteristics. No single psychiatric profile characterised diminished criminal responsibility. Intellectual impairment was one of the most consistent findings across studies. Psychotic disorders occurred among offenders with diminished responsibility but tended to be more strongly associated with severe impairment or absent responsibility. Personality pathology and substance-use disorders were also reported, although their prevalence varied across populations. The findings emphasised the importance of cognitive, volitional, behavioural, and other functional impairments rather than psychiatric diagnosis alone. Conclusions: Diminished criminal responsibility is clinically heterogeneous and cannot be attributed to a specific psychiatric diagnosis. Intellectual impairment appears particularly relevant to intermediate determinations of responsibility, while severe psychotic impairment is more frequently associated with absent responsibility. The forensic significance of psychopathology depends primarily on the extent to which it impairs capacities relevant to criminal responsibility without abolishing them entirely.