Social changes, particularly in mental health policy, may affect the distribution of crime and the legal process. Data for this study were obtained from the prosecutor's office on 2,094 MDOs who were not prosecuted, or whose criminal responsibility was judged as diminished, or who were exempted because of mental disorders. Findings disclosed that: (1) women in the 1994 group were, on average, 4 years older; (2) the female MDOs showed the same tendency as the general population of female offenders toward an increase in the percentage of non-violent crime; (3) the legal process applied to the 1994 group was more simplified than that of 1980; and (4) the 1994 group used significantly more outpatient and community mental health services, highlighting the impact of the social changes in the reform of mental health policy, particularly that of deinstitutionalization. There is no clear evidence of the superiority of hospital care over community care, and it is too early to conclude that Japan has been successful in dealing with the issue of deinstitutionalization. Notes, figure, tables, references