The Lay Judge System was introduced to Japanese courts in 2009, in which laypersons selected from the general population participate in trials. Since then, the courts have requested psychiatric experts to provide clear, concise testimony regarding the mental status of defendants, with focus on the influence of psychiatric symptoms on the commitment of offences. This author aimed to determine the manner in which this principle of inviting psychiatric experts affects current court decisions, using four recent cases as examples. The courts at the first trial of the defendants, recognized that they all had confirmed psychiatric disorders, namely delusional disorder, schizophrenia and substance―induced psychosis. Nonetheless, they ruled that the defendants were fully responsible for their offences and condemned them to death. The main reasons for dismissing the insanity defense were as follows. Although auditory hallucinations and persecutory delusions were evident at the time of the offences, direct influences of these psychotic symptoms on commitment of the offences were not demonstrated, and the court considered that the offences were executed by the operation of free will that was assumed to be intact. This author is very concerned about the possibility that the exculpation of psychiatrically disordered offenders is becoming increasingly narrowed under the present judicial policy.
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