정신장애 범죄자의 심신장애 판단구조에 관한 소고 -일본의 책임능력 판단구조를 중심으로-

The Judgment of criminal responsibility for offenders with mental disorders falls within the realm of normative judgment. Judges are not bound by medical expert opinions and independently make normative assessments based on their own experiences, taking into account all relevant factors such as the motive and circumstances of the crime to determine the offender’s capacity for understanding and decision-making. However, assessing a person's mental state is an area that requires a high degree of expertise. Moreover, determining criminal irresponsibility due to mental disorder is not simply about handling crimes committed by individuals suspected of having mental illness, but rather about answering the question of whether the mental disorder was the cause of the crime. Therefore, although it is undeniable that the legal determination of criminal irresponsibility ultimately falls within the judge’s discretion, such a normative judgment—being a legal concept—must be preceded by an accurate diagnosis of the offender’s mental state to be legitimate and persuasive. In this context, the core of the assessment lies not in diagnosing a specific mental disorder, but in understanding how symptoms manifested by that disorder influenced the criminal act. In practice, however, investigations for determining criminal irresponsibility tend to rely heavily on the defendant’s history prior to the offense. Additionally, psychiatric evaluations often follow general diagnostic procedures used for medical purposes, which has led to criticism that they are not specialized for criminal cases. This raises concerns that judges’ independent normative assessments could become arbitrary. Therefore, mechanisms are needed to mitigate such risks. Collaboration between judges—who are legal professionals—and psychiatrists—who are experts in mental health—is essential, and there is a need to systematize the division of roles, particularly the scope of opinions that psychiatric experts should offer. In Japan, the issue of how far psychiatrists should speak on criminal responsibility and to what extent judges should respect their opinions has long been a matter of debate. Rather than focusing on who should determine criminal responsibility, the emphasis has shifted to how the process should be structured. Interdisciplinary research between psychiatry and criminal law has been actively pursued under this awareness. Efforts have been made to ensure the validity of criminal irresponsibility assessments and the reliability of psychiatric evaluations through the structuring of collaborative processes between legal professionals and psychiatric experts, as well as through the standardization of psychiatric evaluation formats. The determination of criminal irresponsibility lies at the intersection of psychiatry and criminal law. Its legitimacy depends on enhancing the credibility of the evaluation process through efficient collaboration between these two fields. This article, therefore, examines Japan's case as a reference and draws implications by exploring the various measures implemented there to ensure the reliability of legal judgments on criminal irresponsibility through such interdisciplinary collaboration.