Background A relationship exists between mental disorder and offending
behaviours but the nature and extent of the association remains in do
ubt. Method Those convicted in the higher courts of Victoria between 1
993 and 1995 had their pyschiatric history explored by case linkage to
a register listing virtually all contacts with the public psychiatric
services. Results Prior psychiatric contact was found in 25% or offen
ders, but the personality disorder and substance misuse accounted for
much of this relationship. Schizophrenia and affective disorders were
also over-represented, particularly those with coexisting substance mi
suse. Conclusions The increased offending in schizophrenia and affecti
ve illness is modest and may often be mediated by coexisting substance
misuse. The risk of a serious crime being committed by someone with a
major mental illness is small and does not justify subjecting them, a
s a group, to either increased institutional containment or greater co
ercion.