How Does Japanese Law Handle Torts Committed by Multiple Actors (Joint Torts)?

When harm is caused by the actions of more than one person or entity, determining the liability of each involved party can become complex. Japanese law addresses such situations through primarily two frameworks: "concurrent torts" (競合的不法行為 - kyōgōteki fuhō kōi), where individual tortious acts converge to cause harm, and "joint torts" (共同不法行為 - kyōdō fuhō kōi), specifically governed by Article 719 of the Civil Code, which deals with concerted or closely interrelated wrongful acts.

1. Concurrent Torts (Kyōgōteki Fuhō Kōi)

Concurrent torts occur when multiple independent tortious acts by different actors contribute to the same damage, or where their individual liabilities overlap with respect to the same harm. In such cases, the general approach is to assess the liability of each tortfeasor individually based on the standard principles of tort law, typically Article 709 of the Civil Code. The court examines whether each actor committed a distinct tort (i.e., fulfilled the requirements of intent or negligence, causation, infringement of right, and damage) and determines the extent of damages attributable to their specific act.

To the extent that the compensable damages caused by each tortfeasor's independent act overlap and pertain to the same injury suffered by the victim, the tortfeasors are often held to be under what is known as "non-true joint and several liability" (不真正連帯債務 - fushinsei rentai saimu). This means the victim can claim the full amount of the overlapping damage from any one of the liable parties, but once the victim is compensated for that portion of the damage by one party, the liability of the others is extinguished to that extent.

Special Case: Tortfeasor Unidentifiable Among a Group (Civil Code Art. 719(1), latter part)

A specific type of concurrent tort scenario is addressed by the latter part of Article 719(1) of the Civil Code, often referred to as "alternative causation" (択一的競合 - takuitsuteki kyōgō). It states: "The same shall apply if it is impossible to know which of several joint participants (共同行為者 - kyōdō kōisha) inflicted the damage". This provision means such participants are jointly and severally liable.

In this situation, where it's clear that one member of an identified group committed the tort but it's impossible to pinpoint which one, the burden of proof regarding individual causation shifts. The plaintiff typically needs to prove:

1. An infringement of their right and the resulting damages.
2. That the harmful act was committed by one of the identified defendants (e.g., A, B, or C).
3. That no other person outside this group could have committed the act.
4. That each of the potential actors (A, B, and C) acted with intent or negligence with respect to their potential act that could have caused the harm.

Once the plaintiff establishes these points, each defendant in the group then bears the burden of proving that their own specific act did not cause the plaintiff's harm. If a defendant successfully proves this lack of individual causation, they are exonerated; otherwise, they remain jointly and severally liable with the others who cannot disprove their causal role. This is a significant reversal of the usual burden of proving causation.

2. Joint Torts (Kyōdō Fuhō Kōi) (Civil Code Art. 719(1), first part)

The primary provision for "joint torts" is found in the first part of Article 719(1): "If two or more persons have by their joint unlawful act caused damage to another, they are jointly and severally liable to make compensation for such damage". Furthermore, Article 719(2) states that instigators and those who aid or abet the unlawful act are also deemed to be joint tortfeasors and share this joint and several liability. (Many scholars view Article 719(2) as merely confirmatory, as such parties would likely be covered by the "joint unlawful act" concept in 719(1) anyway ).

The precise legal significance and uniqueness of this "joint tort" provision, compared to general concurrent torts, have been a subject of extensive academic debate.

Traditional View vs. Recent/Prevailing View on Joint Tort Uniqueness

• Traditional View (伝統的考え方):
  This perspective generally required that the act of each individual alleged joint tortfeasor independently satisfy all the elements of a tort (intent or negligence, causation leading to the specific damage, etc.). The concept of "jointness"—referred to as "related commonality" (関連共同性 - kanren kyōdōsei)—was seen primarily as a factor that could relax the requirement of "adequacy" (相当性 - sōtōsei) in the causation analysis for each individual. That is, damage that might not be considered an "adequate" or legally significant consequence if viewed as resulting from one person's act alone could become "adequate" when viewed in the context of the joint conduct. Under this view, the plaintiff would still need to prove all elements of a tort against each defendant individually, plus the related commonality of their acts.
• Recent and Prevailing View (最近の考え方):
  This more modern interpretation, which has gained significant traction, particularly influenced by its application in complex pollution and mass tort litigation, critiques the traditional view. If each individual act must constitute a complete tort on its own, then general tort principles (Article 709) would already establish liability, arguably rendering Article 719(1)'s joint tort provision somewhat redundant, save for the potential easing of the "adequacy" aspect of causation.The prevailing modern understanding finds the distinctiveness of Article 719(1) (first part) in its treatment of causation. It posits that for joint tort liability to attach to all participants for the entire harm:Under this recent view, the plaintiff must prove:
  1. There must be "related commonality" (関連共同性 - kanren kyōdōsei) among the acts of the individuals.
  2. There must be a causal link between the overall "joint act" (共同行為 - kyōdō kōi) (viewed as a collective or combined enterprise) and the resulting harm.
     Crucially, this view generally does not require the plaintiff to prove a specific causal link between each individual actor's specific conduct and the entirety of the harm (個別的因果関係 - kobetsuteki inga kankei). Once an actor is found to be part of a "joint unlawful act" that caused the damage, they are typically liable for the whole damage, and the defense that "my specific contribution only caused a part of the harm" is generally not available to escape joint and several liability for the total damage.
1. Infringement of their right and the resulting damages.
2. Intent or negligence on the part of each alleged joint tortfeasor (A, B, C) with respect to their individual acts that formed part of the joint conduct.
3. The "related commonality" of the acts of A, B, and C.
4. A causal link between the joint act of A, B, and C (as a collective) and the infringement/damages.
   The Osaka District Court judgment in the Daito Flood Litigation (First Instance) (February 19, 1976, Hanrei Jihō 805-18) is often cited as a judicial articulation of this approach, emphasizing that requiring proof of individual causation for each actor would render the joint tort provision meaningless, as Article 709 would suffice.

The Meaning of "Related Commonality" (Kanren Kyōdōsei)

A key element for establishing a joint tort under Article 719(1) is "related commonality" between the acts of the multiple tortfeasors. There are two main theories on what this entails:

• Subjective Commonality Theory (主観的共同説 - Shukanteki Kyōdō Setsu): This theory requires a subjective element, such as a meeting of minds, mutual intent, conspiracy, or common design among the actors to act jointly or in concert. The rationale is that holding someone liable for damage also caused by others' acts (as part of a joint endeavor) is justified only if they consciously participated in or accepted the joint nature of the conduct.
• Objective Commonality Theory (客観的共同説 - Kyakkanteki Kyōdō Setsu): This is the prevailing view in case law and among scholars. It posits that a subjective intent to collaborate is not necessary. Instead, an objective connection, interrelation, or convergence of the acts in producing the harm is sufficient. This interpretation is supported by the drafting history of the Civil Code and is seen as more conducive to victim protection by allowing for a broader application of joint tort principles. The Supreme Court, in an obiter dictum in the Sannōgawa River Pollution Case (April 23, 1968, Minshu 22-4-964), suggested support for this objective view by stating that if the acts of multiple parties are objectively related and jointly cause illegal damage, and each act independently fulfills tort requirements, each is liable for damage adequately caused by the illegal conduct.

While the objective theory is dominant, the precise meaning of "objective related commonality" can be somewhat vague. Efforts to provide more concrete criteria have included considering factors such as:

• Spatiotemporal proximity of the acts.
• An "expanded duty of care" among the actors, implying a mutual responsibility to cooperate in avoiding harm to third parties.
• Whether the actors derived a "benefit of aggregation" from their combined actions.
• Whether the actors formed a "risk community" (危険共同体 - kiken kyōdōtai) or an "interest community" (利益共同体 - rieki kyōdōtai) in relation to the harm-causing activity.
  It's important to note that the objective commonality theory does not exclude situations where subjective commonality (e.g., a conspiracy) exists; rather, subjective commonality is sufficient but not a necessary condition for establishing a joint tort.

Effect of Joint Tort: Joint and Several Liability and Its Mitigation

The primary effect of establishing a joint tort under Article 719(1) is that the joint tortfeasors are jointly and severally liable for the entire damage caused to the victim. This means each tortfeasor can be held responsible for compensating the full amount of the victim's loss, regardless of their individual degree of contribution to the harm (subject to adjustments for any comparative negligence on the part of the victim, which is typically assessed relatively against each tortfeasor unless it's a single, indivisible accident scenario ).

Debate on Mitigating Full Joint and Several Liability

The stringency of full joint and several liability, especially where one tortfeasor's contribution might seem minor compared to others, led to discussions about potential mitigation, particularly in the context of widespread traffic accidents and large-scale pollution cases that emerged from the 1960s onwards.

• "Partial Joint Liability" Theory (一部連帯の理論 - Ichibu Rentai no Riron): This early theory suggested that joint liability should only extend to the portion of damage commonly caused by all, with individual liability for any excess damage based on each actor's greater contribution.
• Contribution-Based Reduction (寄与度減責の理論 - Kiyodo Genseki no Riron): A more developed line of reasoning, particularly influential in lower court decisions in pollution cases, involved reducing an individual tortfeasor's share of the liability based on their specific "degree of contribution" (寄与度 - kiyodo) to the overall harm. This was seen not as an issue of causation itself, but as a normative adjustment to the amount of damages for fairness.
  • Special legislation related to air and water pollution (e.g., Air Pollution Control Act, Article 25-2) explicitly allows courts to consider a business operator's "markedly small degree of contribution" when determining their share of damages in joint tort situations.
  • Some lower courts, particularly in pollution litigation, distinguished between "strong related commonality" (強い関連共同性 - tsuyoi kanren kyōdōsei) and "weak related commonality" (弱い関連共同性 - yowai kanren kyōdōsei). For "strong" commonality (e.g., involving subjective elements like collusion or a high degree of individual causal impact), full joint and several liability would apply without reduction. For "weak" commonality (e.g., lacking subjective elements, low individual contribution, where full joint liability seems inequitable), a reduction based on contribution was considered permissible. (e.g., Nishiyodogawa Air Pollution Litigation, Osaka District Court, March 29, 1991, Hanrei Jihō 1383-22 ).
• Supreme Court's Stance (Generally Against Contribution-Based Reduction Vis-à-vis the Victim):
  The Supreme Court has generally been resistant to allowing individual joint tortfeasors to limit their liability towards the victim based on their relative degree of contribution, especially when a true joint tort is established. In a case involving successive torts (a traffic accident followed by medical malpractice, treated as a joint tort), the Court emphasized that Article 719's purpose is to protect victims by allowing them to recover the full amount of their damages from any of the joint tortfeasors. Apportioning the damages among tortfeasors in a way that limits what the victim can recover from any single one would undermine this legislative intent and could contradict the principle of fairness in damage allocation (Supreme Court, March 13, 2001, Minshu 55-2-328). Some scholars argue that situations where courts have allowed contribution-based reduction under the guise of "weak related commonality" might be better analyzed as cases of concurrent (but not truly joint) torts, where individual liability limits are more appropriate.

Right of Recourse Among Joint Tortfeasors

While joint tortfeasors are jointly and severally liable to the victim, Japanese law provides for a right of recourse (求償権 - kyūshōken) among them. If one joint tortfeasor pays more than their "internal share" (負担部分 - futan bubun) of the total damages to the victim, they can seek contribution from the other joint tortfeasors for the excess amount.

The liability among joint tortfeasors is considered a form of "non-true joint and several obligation". The internal share or proportion of liability among the tortfeasors themselves is typically determined based on their respective degrees of fault (過失割合 - kashitsu wariai) or causal contribution relative to each other (e.g., Supreme Court, November 18, 1966, Minshu 20-9-1886; Supreme Court, July 1, 1988, Minshu 42-6-451). Complex recourse scenarios can arise, for example, when employer liability intersects with joint torts (e.g., an employer who pays for their employee's joint tort can seek recourse against the other non-employee joint tortfeasor based on that other tortfeasor's internal share of responsibility).

Effect of Events Concerning One Joint Tortfeasor on Others

Because the liability of joint tortfeasors to the victim is "non-true joint and several," legal events or actions concerning one joint tortfeasor generally do not automatically affect the liability of the others (this is known as "relative effect" - 相対効 - sōtaikō). For example:

• A victim making a demand for payment from one joint tortfeasor does not interrupt the statute of limitations for their claims against the other joint tortfeasors (Supreme Court, March 4, 1982, Hanrei Jihō 1042-87).
• A victim releasing one joint tortfeasor from liability does not automatically release the other joint tortfeasors from their obligations (Supreme Court, November 24, 1994, Hanrei Jihō 1514-82).
  An exception may exist if a release given to one tortfeasor was clearly intended by the victim, based on its terms or surrounding circumstances, to also discharge the obligations of all other tortfeasors concerning the released portion of the debt.

Conclusion

Japanese law provides distinct but sometimes overlapping frameworks for addressing harm caused by multiple actors. "Concurrent torts" involve the aggregation of individual liabilities, with a special rule shifting the burden of disproving causation in cases where the specific injurer within a group is unknown. "Joint torts" under Article 719 of the Civil Code impose stringent joint and several liability on those whose acts exhibit a "related commonality" and collectively cause harm, a principle broadly interpreted to enhance victim protection. While debates persist regarding the precise scope of "jointness" and the possibility of mitigating full liability for minor contributors vis-à-vis the victim, the overarching goal is to ensure victims can obtain full compensation. Internally, however, joint tortfeasors do have rights of recourse against each other based on their relative degrees of fault, ensuring a secondary allocation of the ultimate financial burden.