Background: Previous studies have led to suggestions that there are at least three sub-types of offenders with schizophrenia, but these have not previously been examined simultaneously in one sample. Aims: The aims of this study were to investigate categorisation of offenders with psychosis as early or late starters or late first offenders, and test the hypotheses that, compared with non-offenders with psychosis, early starters would be characterised by low educational or occupational achievement, negative childhood experiences and early substance use, whereas positive psychotic symptoms would characterise late starters or late first offenders. Methods: A retrospective file study was conducted, yielding 97 early starters, 100 late starters and 26 late first offenders identified from a specialist inpatient forensic mental health assessment service and 129 non-offenders identified from general psychiatric services in the same geographic region, all with schizophreniform psychoses. Results: We found little difference between early and later starters in terms of measured antecedents, but substance misuse was up to 20 times less likely among late first offenders. Persecutory and/or grandiose delusions were more strongly associated with each offender group compared with non-offenders, most so with late first offenders. Conclusions: Our findings underscore the importance of treating delusions - for safety as well as health. Childhood antecedents may be less important indicators of offender sub-types among people with psychosis than previously thought. When patients present with grandiose or persecutory delusions over the age of 35years without co-morbid substance misuse disorders, but with a history of childhood neglect and low educational achievement, particular care should be taken to assess risk of violence.