In criminal trials, persons who, due to mental disability, are unable to discern between right and wrong in their own actions, or are able to make such discernment but are unable to act on it, are treated as insane persons and may therefore not be punished. Also, persons whose ability to make such discernment or to act on such discernment is extremely limited are treated as quasi-insane persons, and their punishment is mitigated accordingly.
  Under the Law concerning Mental Health and Welfare of Mentally Disabled Persons (referred to as the "Mental Health and Welfare Law" for the purpose of this Chapter), public prosecutors, the directors of probation offices and the wardens or the superintendents of correctional institutions shall notify the relevant prefectural governor of any person who is mentally disabled or suspected to be mentally disabled. The governor may have the person admitted to a mental hospital or designated hospital established by the country or the prefecture (involuntary admission to mental hospital), provided that there is an agreement on the results of diagnosis by two or more designated doctors, indicating that the person is mentally disabled and poses a risk of injury to him/herself or to others.