Identifying factors associated with criminal responsibility by analyzing court trial verdicts

The criminal responsibility of offenders with mental disorders is a key issue in forensic psychiatry. Japan's implementation of the Medical Treatment and Supervision Act and Lay Judge Act in the early 2000s raised public awareness of this issue. To determine how criminal court judges in Japan assess the criminal responsibility of offenders, we examined 453 district court verdicts that mention psychiatric evidence. We extracted elements from each verdict that may be associated with courts' decision-making regarding criminal responsibility and analyzed the relationship between each element and the adjudication of criminal responsibility. We investigated the changes in each element's prevalence over time. A logistic regression analysis revealed that the following were independently associated with the court decisions that offenders' criminal responsibility was intact: understandable motivation for committing the offense, homogeneity of the offense from the defendant's usual behavioral pattern, a coherent process used to commit the offense, alertness while offending, and absence of psychotic symptoms. We observed that recent verdicts are more focused on the offender's perception of illegality and the coherence of the offending process while disregarding the defendant's consciousness and memory while offending. Thus, the courts focus on some specific elements for evaluating the criminal responsibility of each offender.