What are "Indirect Facts" and "Auxiliary Facts" in Japanese Evidence Law, and How Do They Help Prove a Case?

Japanese Attorney at Law - Bengoshi L.L.

• 8 min read

In any civil lawsuit in Japan, the ultimate goal of presenting evidence is to convince the court of the truth of certain "principal facts" (shuyō jijitsu 主要事実)—those core factual elements that directly establish a legal right or defense. However, direct evidence proving these principal facts is not always available. This is where the concepts of "Indirect Facts" (kansetsu jijitsu 間接事実) and "Auxiliary Facts" (hojo jijitsu 補助事実) become crucial. These categories of facts, while not directly constituting the elements of a claim or defense, play vital roles in the inferential reasoning process and in assessing the reliability of evidence, thereby helping parties build a persuasive case and enabling the court to reach a just decision under the Principle of Free Evaluation of Evidence.

I. The Landscape of Facts in Japanese Civil Litigation: Beyond Direct Proof

A. The Goal: Establishing "Principal Facts" (Shuyō jijitsu - 主要事実)

Before delving into indirect and auxiliary facts, it's essential to reiterate what "principal facts" are:

  • Definition: Principal facts are the specific factual elements that, under the applicable substantive law, directly give rise to, modify, or extinguish the legal rights or obligations being disputed in the lawsuit. They are the ultimate facts that a plaintiff must prove to succeed in their claim, or that a defendant must prove to establish an affirmative defense.
  • Examples:
    • In a breach of contract claim: the formation of a valid contract, the specific terms breached, the act of breach, and the resulting damages.
    • In a tort claim: the defendant's negligent or intentional act, the plaintiff's injury/damage, and the causal link between the act and the injury/damage.
  • Subject to the Principle of Party Presentation (Benron-shugi 弁論主義): As discussed previously, principal facts must be alleged by the parties, and judicial admissions concerning them are generally binding on the court. The burden of proof (shōmei sekinin 証明責任) also primarily relates to establishing these principal facts.

B. The Challenge of Proving Principal Facts Directly
Often, direct, unequivocal evidence for every principal fact is unavailable. For example, there might be no single document or eyewitness that conclusively proves a party's subjective intent or the precise cause of a complex failure. Litigants must then build their case by other means.

II. Indirect Facts (Kansetsu jijitsu - 間接事実): Building a Case Through Inference

Indirect facts are the evidentiary building blocks often used to construct a compelling argument for the existence (or non-existence) of a principal fact.

A. Definition and Role

  • Definition: An indirect fact is a fact that, while not itself a direct element of the legal claim or defense, serves as a basis from which a principal fact can be inferred, either alone or in conjunction with other indirect facts. This inference is made by applying rules of logic and general experience (keiken-soku 経験則 – empirical rules or common-sense principles).
  • Nature: Indirect facts are essentially circumstantial evidence presented in the form of factual propositions. They create a chain of reasoning leading towards a principal fact.
  • Role: Their primary role is to increase or decrease the probability of a principal fact being true. A strong accumulation of consistent indirect facts can lead a judge to a "high degree of probability" (kōdo no gaizen-sei 高度の蓋然性) regarding a principal fact, even without direct proof.

B. How Indirect Facts Work: The Process of Inference (Suinin - 推認)
The court uses indirect facts to "infer" (suinin suru 推認する) principal facts.

  • Example 1 (Contract Formation):
    • Principal Fact to Prove: A valid oral contract was formed.
    • Potential Indirect Facts:
      • Evidence of extensive prior negotiations between the parties.
      • A draft written agreement that was discussed but never signed.
      • Conduct of the parties subsequent to the alleged agreement that is consistent with its existence (e.g., partial performance).
      • Witness testimony about conversations where key terms were seemingly agreed upon.
      • Industry custom regarding similar oral agreements.
        No single indirect fact here might be conclusive, but together they can create a strong inference that the oral contract (a principal fact) was indeed formed.
  • Example 2 (Negligence):
    • Principal Fact to Prove: The defendant acted negligently.
    • Potential Indirect Facts:
      • The defendant violated an internal safety protocol.
      • The defendant had received prior warnings about a similar risk.
      • The type of accident that occurred rarely happens in the absence of negligence.
      • The defendant took subsequent remedial measures (though admissibility and weight of this can be complex).

C. Party Presentation (Benron-shugi) and Indirect Facts

  • While the strict requirement for party allegation under Benron-shugi applies primarily to principal facts, parties are responsible for alleging and offering evidence of the indirect facts they wish the court to consider in support of (or against) a principal fact.
  • However, courts in Japan generally have more flexibility with indirect facts. If evidence properly submitted for one purpose reveals other relevant indirect facts not explicitly pleaded by a party, the court may still consider these indirect facts in its overall evaluation, provided doing so does not cause undue surprise or prejudice to the opposing party (often balanced by the court's power of clarification - shakumei-ken 釈明権, to ensure parties can address such emergent facts).

D. Using Indirect Facts in Business Litigation: Common Scenarios

  • Proving Intent or Knowledge: In cases like fraud, bad faith infringement of intellectual property, or certain types of anti-competitive behavior, a party's subjective state of mind (a principal fact) is often proven through indirect facts (e.g., suspicious timing of actions, access to confidential information, prior similar conduct).
  • Establishing Causation in Complex Cases: In product liability or environmental damage cases, where direct proof of causation can be scientifically challenging, a chain of indirect facts (e.g., exposure to a substance, statistical correlation, elimination of other causes) may be used to infer causation.
  • Interpreting Ambiguous Contractual Terms: The parties' conduct during negotiations, their post-contractual behavior, and relevant industry customs (all indirect facts) can be crucial for inferring the intended meaning of an ambiguous contractual provision (a principal fact regarding the contract's terms).

III. Auxiliary Facts (Hojo jijitsu - 補助事実): Assessing the Credibility and Weight of Evidence

Auxiliary facts do not directly prove or disprove principal facts, nor do they form links in an inferential chain towards principal facts. Instead, their role is to affect the probative value (credibility and weight - shōmei-ryoku 証明力) of other pieces of evidence.

A. Definition and Role

  • Definition: An auxiliary fact is a fact that tends to strengthen or weaken the reliability or persuasiveness of a specific piece of evidence (e.g., a particular document, a witness's testimony, an expert opinion).
  • Role: They help the court determine how much trust or reliance to place on a source of proof when making its findings on principal or indirect facts.

B. How Auxiliary Facts Work: Enhancing or Impeaching Evidence

  1. Positive Auxiliary Facts (Enhancing Probative Value):
    • Example (Witness): The witness has a reputation for honesty, has no personal or financial interest in the outcome of the litigation, their memory of the event is fresh, their testimony is internally consistent and detailed.
    • Example (Document): The document was created contemporaneously with the events by a person with direct knowledge, it was kept in the ordinary course of business under a reliable system, there are multiple consistent copies.
  2. Negative Auxiliary Facts (Diminishing Probative Value / Impeachment):
    • Example (Witness): The witness has a clear bias (e.g., close family member of a party, an employee whose job is at stake), they have made prior inconsistent statements, their testimony is vague or contradictory, their opportunity to observe was limited, they have a criminal conviction for perjury.
    • Example (Document): The document's authenticity is questionable (e.g., signs of alteration, suspicious origin), it was created long after the event by someone with a motive to misrepresent, there are conflicting versions, a party delayed significantly in producing it without good reason.

C. Party Presentation (Benron-shugi) and Auxiliary Facts

  • Parties actively introduce evidence of auxiliary facts to bolster the credibility of their own evidence and to impeach (attack the credibility of) the evidence presented by their opponent. For instance, during cross-examination of an opponent's witness, a party will try to elicit testimony about auxiliary facts that undermine that witness's credibility.
  • The strict rules of Benron-shugi regarding party allegation do not apply to auxiliary facts in the same way they apply to principal facts. The court, under the Principle of Free Evaluation of Evidence (Jiyū shinshō-shugi 自由心証主義), has broad discretion to consider any information or circumstances relevant to assessing the weight and credibility of evidence, whether or not those specific "auxiliary facts" were formally pleaded as such.

D. Using Auxiliary Facts in Business Litigation

  • Challenging Witness Credibility: Demonstrating an employee-witness's strong loyalty to their company or potential for personal gain/loss depending on the outcome.
  • Validating Documentary Evidence: Showing that internal accounting records were maintained consistently according to established procedures and regularly audited.
  • Questioning Expert Witnesses: Examining an expert's qualifications, potential conflicts of interest, the data they relied upon, or flaws in their methodology.
  • Explaining Delays or Gaps in Evidence: If certain documents are missing, providing a credible explanation (an auxiliary fact) can mitigate potential adverse inferences.

IV. The Role of General Experience and Logic (Keiken-soku / Ronri-hōsoku - 経験則・論理法則)

The bridge between indirect facts and principal facts, and the tool for assessing probative value based on auxiliary facts, is the application of "rules of general experience" (keiken-soku 経験則) and "rules of logic" (ronri-hōsoku 論理法則).

  • Foundation of Inference and Evaluation: Judges are expected to use their common sense, understanding of human behavior, basic scientific principles (where applicable and commonly known), and logical reasoning when making these connections and assessments.
  • Constraint on Free Evaluation: While Jiyū shinshō-shugi grants judges freedom in how much weight to give evidence, their overall reasoning process must be rational and consistent with established logic and widely accepted empirical knowledge. An inference that is illogical or defies common experience can be a ground for an appellate court to find an error in fact-finding.

V. Interplay in the Fact-Finding Process

  1. Building a Persuasive Narrative: Successful litigation involves more than just presenting isolated pieces of evidence. Litigants construct a coherent and persuasive narrative by:
    • Clearly alleging the principal facts they seek to establish.
    • Supporting these with direct evidence where possible.
    • Where direct evidence is lacking or weak, building a strong inferential case by proving a compelling set of interconnected indirect facts.
    • Bolstering their own key evidence by highlighting positive auxiliary facts.
    • Undermining the opponent's key evidence by exposing negative auxiliary facts.
  2. The Court's Holistic Evaluation: The judge's task is to consider all three types of facts, the evidence presented for each, the arguments of the parties, and the "entirety of oral arguments" (kōtō benron no zen shushi 口頭弁論の全趣旨 – the overall impression from the hearings) to form an inner conviction (shinshō 心証) about the truth of the principal facts, to the standard of "high degree of probability."
  3. Relationship with Burden of Proof (Shōmei sekinin 証明責任): A party bearing the burden of proof for a principal fact will often rely heavily on proving a robust chain of indirect facts that makes the principal fact highly probable. The opponent, in turn, will try to break that chain or offer alternative explanations consistent with the indirect facts but negating the alleged principal fact.

VI. Strategic Considerations for Businesses

  • Don't Rely Solely on "Smoking Guns": Recognize that direct, incontrovertible evidence is rare. Be prepared to build your case circumstantially using indirect facts.
  • Thorough Factual Investigation is Key: Before and during litigation, investigate not only facts that directly prove your claim or defense but also those seemingly minor facts that could corroborate your main points or undermine your opponent's.
  • Focus on Credibility: Pay close attention to auxiliary facts that can bolster your witnesses and documents, and identify weaknesses in your opponent's.
  • Articulate Inferences Clearly to the Court: In legal briefs and oral arguments, do not assume the judge will automatically draw the inferences you want from the indirect facts. Explicitly connect the dots and explain the logical and experiential basis for your proposed inferences.
  • Challenge Unreasonable Inferences by the Opponent: If your opponent is attempting to build a case on weak or illogical inferences from indirect facts, clearly point out these flaws.

Conclusion

The distinction between principal facts, indirect facts, and auxiliary facts provides a sophisticated yet practical framework for understanding the intricate process of proof and fact-finding in Japanese civil litigation. While principal facts are the ultimate destination, indirect facts often pave the inferential road, and auxiliary facts act as the quality control for the evidence used on that journey. For businesses, a nuanced appreciation of how to strategically identify, marshal, and argue all three types of facts, always grounding arguments in logic and general experience, is fundamental to constructing a compelling and ultimately successful case before a Japanese court.