Joint Crime, Individual Defenses: Japan's Supreme Court on Co-Principals and Self-Defense

Case: The Supreme Court of Japan, Second Petty Bench, Case No. 1990 (A) 788
Decision Date: June 5, 1992

In a foundational decision clarifying the principles of complicity in Japanese criminal law, the Supreme Court of Japan addressed a critical question: when one participant in a joint crime acts in excessive self-defense, does that defense automatically extend to their co-conspirator? The Court's unequivocal answer was no. The ruling established that legal defenses are not contagious; they must be assessed individually for each participant based on their unique circumstances and state of mind, particularly their intent upon entering the conflict.

The Facts: A Dispute Escalates to Tragedy

The case began with a seemingly minor slight. The defendant, X, was at a friend's apartment when he called a female friend at her workplace, a restaurant. The restaurant's manager, A, admonished X for the long call and abruptly hung up the phone. Enraged by this, X repeatedly called back, demanding to speak to his friend. A refused and allegedly insulted X, which further fueled his anger.

Incensed, X resolved to confront A at the restaurant. He persuaded his reluctant friend, Y, to accompany him. Critically, X armed Y with a kitchen knife (with a blade length of approximately 14.5 cm) before they left for the restaurant in a taxi.

During the taxi ride, the conspiracy solidified. Although X himself had never met A and did not know what he looked like, he instructed Y, "I'm known there, so you go in first. If a fight breaks out, I won't abandon you." X then escalated his instructions, demonstrating a contingent intent to kill A. He told Y, "If you get hit, use the knife."

Upon arriving near the restaurant around 5:00 AM, X directed Y to wait near the entrance while he himself stayed a short distance away, talking with the female friend who had just emerged from the establishment. Y, who also had no prior acquaintance with A, waited as instructed, thinking it unlikely he would be assaulted without provocation.

Contrary to his expectations, A emerged from the restaurant and, mistaking Y for X, immediately attacked him. A grabbed Y by the collar, dragged him around, punched him in the face with his fists, and, after knocking him to the concrete, began kicking him. Y fought back but was overpowered and knocked down again. Fearing for his life and body, and with no help from X, Y acted in a desperate attempt to defend himself. Recalling X's instructions, he decided that even killing A was unavoidable. Acting on the conspiracy with X, Y pulled out the knife and stabbed A multiple times in the left chest and other areas. A died from blood loss due to a punctured heart and liver.

The Lower Courts: A Shifting View of Intent and Defense

The path of the case through the lower courts reveals a developing analysis of each participant's culpability.

The District Court (Tokyo): The first-instance court found both X and Y guilty of murder. It determined that a conspiracy to murder, with at least conditional intent (dolus eventualis), was formed in the taxi. The court denied the claim of self-defense for both men. It reasoned that because both had approached the scene with an "aggressive intent," the subsequent attack by A could not be considered an "imminent and unjust infringement" that would trigger the right to self-defense under Article 36 of the Penal Code.

The High Court (Tokyo): On appeal, the High Court partially amended the lower court's judgment. It affirmed that Y was guilty of murder but granted him a reduced sentence on the grounds of excessive self-defense (Article 36, Paragraph 2). The High Court’s reasoning was that Y's personal intent to kill was only formed at the precise moment he was being violently assaulted by A. Before that point, Y did not possess an "aggressive intent." Therefore, from Y's perspective, A's violent assault did constitute an "imminent and unjust infringement." While Y's response with a knife was disproportionate and thus excessive, the foundational requirement for the defense was met.

However, the High Court refused to extend this defense to X. It found that X, unlike Y, had anticipated the conflict and approached it with clear aggressive intent. X had orchestrated the confrontation with the goal of having Y counter-attack with the knife if an opportunity arose. For X, the situation was not a sudden emergency but a planned eventuality.

X appealed to the Supreme Court, arguing that as a co-principal, he should benefit from the finding of excessive self-defense granted to Y.

The Supreme Court Decision: The Individualization of Defenses

The Supreme Court rejected X's appeal and upheld the High Court's decision, cementing a vital principle of Japanese criminal law.

The Court's central thesis was stated with absolute clarity: "The applicability of excessive self-defense in cases of joint perpetration should be determined by examining whether the requirements are met for each co-principal individually. The fact that excessive self-defense is established for one co-principal does not mean that it is automatically established for the other co-principals."

The Court then applied this principle by dissecting the roles and mental states of X and Y:

• For Y: The assault by A was an "imminent and unjust infringement." Y had no initial aggressive intent and was the victim of a sudden, mistaken, and violent attack. His action was a response to a direct threat to his life and body. This established the prerequisite for a self-defense claim.
• For X: The exact same assault by A on Y did not constitute an "imminent and unjust infringement" from X's perspective. The Court found that X had "approached the infringement with aggressive intent." He had anticipated that A might attack, and he planned to use that very attack as a pretext to have Y retaliate with the knife. For X, the event was not "imminent" in the sense of being an unforeseen emergency. It was a foreseen, and indeed desired, opportunity to inflict harm on A.

The Court referenced its own 1977 precedent, which held that a person who anticipates an attack and confronts it with aggressive intent cannot claim the "imminence" required for self-defense. X's actions fell squarely within this precedent. He was not a defender but an instigator.

Legal Analysis: The Relativity of Illegality

This decision is a powerful illustration of the principle that in criminal law, justifications for an act are not absolute but can be relative to the individual participant. A long-standing maxim in Japanese criminal theory posits that "illegality is collective, while responsibility is individual." This generally means that if an act is illegal (e.g., a killing), it is illegal for all participants, but the degree of personal blame (responsibility) can differ based on factors like intent or duress.

This case challenges the simplicity of that maxim. Here, the act of killing A was viewed through two different legal lenses. For Y, the act was deemed only partially illegal, as it was committed under the justifying circumstances of self-defense (albeit excessively). For X, the very same act was deemed fully illegal, without any mitigating justification. The "illegality" itself was not uniform or collective; it was individualized.

The core reason for this divergence lies in X's role as the architect of the conflict. X's preparatory actions—goading the reluctant Y, arming him, and directing him into the confrontation—were not acts in furtherance of protecting Y. To the contrary, they created the danger to Y's life and body that had not previously existed. X's goal was to bring about harm to A, using Y's predictable defensive reaction as the instrument. An individual cannot engineer a dangerous conflict and then claim the benefit of a legal justification that arises from that very danger. This is analogous to the common law concept of "provocation" or the doctrine of "unclean hands," where a party who wrongfully creates a situation cannot then rely on it for legal protection.

In essence, the Supreme Court evaluated X's entire course of conduct, from his initial anger to the fatal instructions in the taxi. It saw his liability as stemming from this whole chain of events, which constituted a fully illegal act of realizing a homicide through the manipulation of another person and the exploitation of a conflict he himself had sought out.

Conclusion

The Supreme Court's 1992 decision provides a clear and enduring rule for cases involving co-principals. Legal justifications such as self-defense are deeply personal and are not transferable between participants in a crime. Each individual's criminal liability is determined by their own actions, their own intent, and their own relationship to the circumstances of the offense. One who enters a conflict with aggressive intent, seeking to provoke or exploit a violent response, forfeits the right to claim self-defense. The ruling reinforces the fundamental principle of individual accountability and demonstrates that the law will look past the final act to scrutinize the culpability of those who set the stage for violence.