In Japanese criminal law, the right to defend oneself or others against an unlawful attack is a well-established principle. Known as "legitimate defense" (正当防衛 - seitō bōei), it can fully justify actions that would otherwise be criminal. However, situations often arise where the defensive force used exceeds what was necessary, leading to the complex legal doctrine of "excessive defense" (過剰防衛 - kajō bōei). This is particularly intricate when defensive actions continue even after the immediate threat has subsided—a scenario referred to as "post-facto excess" (事後的過剰 - jigoteki kajō).

Understanding these concepts is not only relevant for individuals but can also provide U.S. corporate legal and business professionals with insights into the Japanese criminal justice system's approach to justification, excuse, and the limits of permissible conduct under pressure. This knowledge can be valuable in assessing risks related to employee conduct or understanding the legal framework surrounding responses to imminent threats more broadly.

The Legal Framework: Self-Defense and Excessive Defense in the Criminal Code

The foundation for these defenses is found in Article 36 of Japan's Criminal Code:

• Article 36, Paragraph 1 (Legitimate Defense - Seitō Bōei): "An act unavoidably performed to protect the rights of oneself or any other person against an imminent and unlawful infringement is not punishable."
  • Key Requirements:
    1. Imminent and Unlawful Infringement (急迫不正の侵害 - kyūhaku fusei no shingai): The danger must be immediate and the attack unjustified by law.
    2. Defensive Intent (防衛の意思 - bōei no ishi): The act must be performed for the purpose of defending against the infringement.
    3. Necessity and Reasonableness (「やむを得ずにした行為」- yamu o ezu ni shita kōi - an unavoidable act): The defensive act must be necessary to avert the danger and proportionate to the threat. It should be the least harmful means available that is effective.
  • Legal Effect: If all conditions are met, the act is justified, meaning no crime is committed, and it is not punishable.
• Article 36, Paragraph 2 (Excessive Defense - Kajō Bōei): "Punishment for an act that exceeds the limits of defense may be reduced or remitted according to the circumstances."
  • "Exceeds the Limits of Defense" (防衛の程度を超えた行為 - bōei no teido o koeta kōi): This occurs when the defensive measures are disproportionate to the threat, either in terms of the intensity of force used or, crucially for this discussion, its continuation beyond the point of necessity.
  • Legal Effect: An act of excessive defense is still considered unlawful. However, the law recognizes that the actor was responding to an unlawful infringement, which can diminish their culpability. Therefore, the court has the discretion to reduce the punishment or even exempt the person from punishment altogether. The theoretical basis for this mitigation (e.g., reduced illegality versus reduced culpability) is a subject of ongoing academic debate.

The Challenge of "Post-Facto Excess" (Jigoteki Kajō)

"Post-facto excess" specifically refers to situations where defensive actions persist after the unlawful infringement has objectively ceased. For example, an attacker is repelled and is no longer posing a threat, but the defender continues to strike them. This raises difficult questions:

• When exactly does an "imminent" threat end?
• Can acts committed after this point still be considered part of the defensive encounter for the purpose of Article 36(2)?

Determining the End of an Infringement

Traditionally, whether an infringement was "imminent" or had "ceased" was often viewed from an objective standpoint after the fact. However, judicial practice and academic discourse have recognized the need for a more nuanced approach:

• The Defender's Perspective (at the time of the act): Some court decisions, such as a Tokyo High Court ruling on July 15, 2015 (Heisei 27.7.15), have emphasized evaluating the situation as it would have appeared to a reasonable person in the defender's position at the moment the defensive act was taken (an ex-ante perspective - 事前的判断 jizenteki handan). This acknowledges that in the heat of the moment, it may not be immediately clear that an attacker has been completely incapacitated or has abandoned their hostile intent.
• A Continuous Series of Defensive Acts: Courts may also consider a rapid sequence of defensive actions as a single, continuous response, even if the final blow technically lands fractionally after the objective cessation of the attacker's immediate capability. The idea is that a defensive response to an ongoing attack might not be divisible into perfectly timed, discrete segments. This often applies to acts occurring in "a very short time and as an unbroken, integrated counterattack" (断絶のない一連一体の反撃行為 - danzetsu no nai ichiren ittai no hangeki kōi).

True "post-facto excess" generally refers to defensive conduct that continues after a reasonable assessment (even from an ex-ante perspective) would indicate the threat has ended, and beyond any such tightly connected final defensive action.

The "Series of Acts" (Ichiren no Kōi) Debate and Its Limits

In Japanese legal academia, particularly following some key Supreme Court decisions around 2008-2009, there has been significant discussion about the "series of acts" theory. This theory suggests that a closely connected sequence of actions should sometimes be evaluated as a single, indivisible unit for the purpose of determining criminal liability.

However, applying this theory to post-facto excessive defense can be problematic:

• Supreme Court, June 25, 2008 (Heisei 20.6.25): In this influential case, the Court distinguished between a first act of violence by the defendant (committed while the infringement was ongoing) and a second act of violence (committed after the infringement had ceased). Despite the temporal and spatial continuity, the Court indicated that if the "defensive intent" (bōei no ishi) was absent for the second act, that act could not be treated as excessive defense but rather as a separate unlawful act. This decision demonstrated a willingness to "sever" acts within a continuous sequence based on the actor's intent and the objective circumstances.
• Critique of Overemphasis: Some scholars argue that an overemphasis on whether acts form a single "social episode" can obscure the more critical question: does the post-facto portion of the conduct still possess the necessary characteristics to qualify for the mitigated treatment under Article 36(2)? The mere fact that actions are closely connected in time and place does not automatically mean they share the same legal character, especially if the actor's intent or the objective justification changes.

The core issue is not just the social perception of the event as one continuous incident, but the legal characterization of each phase of the conduct, especially the actions taken after the initial threat has passed.

Justified Initial Defense vs. Subsequent Excess: Avoiding Unfair "Bundling"

A significant point of contention in the discussion of post-facto excess is how to treat a situation where the defender's initial actions (while the threat was imminent) were perfectly justified under Article 36(1), but their subsequent actions (after the threat ceased) were excessive.

• The "Bundling" Problem: If the entire sequence—the justified initial defense and the subsequent post-facto excess—is treated as a single instance of "excessive defense," this can lead to an unfair outcome. "Excessive defense," while subject to mitigation, is still an unlawful act. Treating an initially justified, non-criminal act as part of an overall unlawful (albeit mitigated) act effectively means that the justified portion is retroactively tainted and, in a sense, punished. This is particularly problematic if the most serious harm caused by the defender occurred during the initial, justified phase.
• Focus on Distinguishing Phases: A more analytically sound approach, advocated by some scholars, is to separately evaluate the legality of the actions taken during the imminent threat and those taken after its cessation.
  • If the acts during the imminent threat fulfilled all requirements of legitimate defense (Article 36(1)), those acts are justified and not punishable.
  • The acts committed after the threat ceased should then be assessed independently. Do they constitute excessive defense under Article 36(2) (if they still possess some "defensive character" and were driven by the preceding attack)? Or, have they transformed into a new, separate unlawful act (e.g., retaliation) devoid of defensive justification?
• Importance of Causal Link and Proof: In cases where it's unclear precisely when a particular injury was inflicted (during the justified phase or the later excessive phase), an approach that bundles everything into a single "excessive defense" risks unfairly attributing harm caused by a justified act to an unlawful (though mitigated) one. This runs contrary to principles of fairness and the presumption of innocence regarding any specific portion of conduct.

The Rationale for Mitigating Excessive Defense: Application to Post-Facto Acts

The legal basis for reducing or remitting punishment for excessive defense is crucial for understanding how post-facto excess is treated. Two main theories exist:

1. Reduced Illegality Theory (違法減少説 - Ihō Genshōsetsu): This theory suggests that an act of excessive defense, while still unlawful, is "less illegal" than an ordinary crime because it originates from a situation of defending a legitimate interest against an unlawful attack. However, this theory faces challenges in justifying mitigation for purely post-facto acts, as the element of protecting a present legal interest against an imminent threat is, by definition, absent once the threat has ceased.
2. Reduced Culpability Theory (責任減少説 - Sekinin Genshōsetsu): This theory focuses on the actor's state of mind. It argues that the fear, agitation, confusion, or excitement caused by the unlawful infringement can diminish the actor's culpability or their capacity to act strictly within the bounds of law. This perspective can more readily accommodate post-facto excess, provided the psychological impact of the attack reasonably continues to influence the actor's behavior, and their actions retain some "defensive character."

Many contemporary analyses lean towards the reduced culpability theory, or a combination, as better explaining the mitigation for excessive defense, especially in complex scenarios like post-facto excess. The key is often whether the post-facto acts, even if objectively no longer necessary for defense against an ongoing threat, can still be understood as an overreaction stemming from the initial defensive situation, rather than a detached, purely aggressive new act.

The Role of "Defensive Intent" in Post-Facto Actions

As highlighted by the Supreme Court (Heisei 20.6.25), the continuation of "defensive intent" into the post-facto phase is critical. If, after the threat ends, the actor's intent shifts from defense to clear retaliation, revenge, or further unprovoked attack, the subsequent actions are unlikely to qualify as excessive defense.

However, "defensive intent" in the context of post-facto excess is not necessarily about the actor still perceiving an active, ongoing threat. Rather, it can refer to a state where the actions are still an extension or an over-continuation of the mindset and behavior initiated in response to the original unlawful infringement, and this defensive orientation has not been entirely replaced by a purely aggressive or retaliatory motive. The actor might be acting under the lingering psychological effects of the attack, "carried away by the momentum" of the defense.

Legal Characterization of Post-Facto Defensive Actions

Given these complexities, actions taken after an imminent threat has ceased can lead to several potential legal outcomes:

1. Legitimate Defense + Subsequent Excessive Defense: The initial actions during the imminent threat were fully justified (Article 36(1)). The subsequent actions, taken after the threat ceased but still linked to the defensive encounter and possessing some "defensive character" (e.g., driven by lingering fear or confusion, not pure malice), exceed the limits and are treated as excessive defense (Article 36(2)), with potential mitigation of punishment.
2. Legitimate Defense + Subsequent Separate Unlawful Act: The initial actions were justified. However, the subsequent actions taken after the threat ceased are found to lack any defensive character and are motivated by retaliation or other non-defensive purposes. These are treated as new, distinct criminal offenses, fully punishable according to their nature.
3. Unitary Excessive Defense: The entire sequence of events, from the commencement of the defensive action through the post-facto continuation, is viewed as a single, continuous defensive episode that, when considered globally, exceeded the necessary limits. This approach is often criticized if it results in the initial, objectively justified portion of the defense being treated as part of an unlawful act, thereby denying full justification where it was due.
4. No Defensive Character for Post-Facto Acts (Full Criminal Liability): If the post-facto acts are clearly detached from any defensive purpose and constitute a new aggressive assault, they will be treated as straightforward criminal offenses without any mitigation related to the prior defensive context.

An older Supreme Court precedent (Taisho 14.12.15 - December 15, 1925) illustrated a bifurcated approach, finding an initial act of stabbing an attacker with a wrested knife to be legitimate defense, while a subsequent pursuit and further stabbing after the attacker had fled was deemed excessive defense. This historical approach supports the idea of analyzing the phases of the encounter distinctly.

Relevance to Corporate Understanding

While excessive defense scenarios typically involve individual altercations, the principles at play offer broader insights for corporate understanding of the Japanese legal system:

• Employee Conduct: If an employee is involved in a situation requiring self-protection (whether on or off duty, if it leads to legal consequences that might affect the company), understanding how Japanese law assesses the limits of defensive force is important for evaluating potential liabilities and defenses.
• Standard of "Unavoidable Acts": The concept of an "unavoidable act" (yamu o ezu ni shita kōi) in legitimate defense reflects a legal standard that assesses actions taken under duress or in response to immediate threats. While not directly translatable to corporate decision-making in all crises, it provides a lens into how the legal system approaches situations where actions are taken under extreme pressure to protect significant interests. The law recognizes that in such moments, perfect judgment or the use of the absolute minimum force might not always be achievable, leading to doctrines like excessive defense that acknowledge human fallibility under pressure.
• Importance of Intent and Context: The emphasis on "defensive intent" and the detailed contextual analysis in these cases highlight that Japanese criminal law often looks beyond the mere physical act to understand the actor's state of mind and the surrounding circumstances. This is a general feature of Japanese criminal jurisprudence that can be relevant in assessing various types of conduct.

Conclusion

The doctrine of excessive defense in Japan, particularly concerning actions that continue after an immediate threat has passed ("post-facto excess"), is a complex area of criminal law. It involves a careful balancing of the right to self-protection against the need to prevent disproportionate harm. Courts and legal scholars continue to grapple with defining the precise boundaries, focusing on factors such as the cessation of the threat, the actor's continuing intent, the psychological impact of the initial attack, and whether subsequent actions retain a "defensive character." While direct application to corporate liability is limited, understanding these principles offers valuable insight into the Japanese legal system's approach to justification, excuse, and the assessment of conduct under pressure.