Challenging a Final Judgment in Japan: When is a Retrial (Saishin) Possible?

Japanese Attorney at Law - Bengoshi L.L.

31 May 2025 • 10 min read

The principle of finality is a cornerstone of any mature legal system. Once a court judgment becomes final and binding, it establishes legal certainty and brings an end to the dispute between the parties. In Japan, this finality is embodied in the doctrine of res judicata (kihanryoku). However, the pursuit of justice sometimes requires a mechanism to correct grave errors that may have tainted a final judgment, especially when such errors could not have been addressed through the ordinary appellate process or came to light only after the judgment was no longer appealable. Japanese civil procedure provides such an extraordinary remedy: the action for retrial, known as saishin (再審). This article explores the stringent conditions under which this exceptional avenue for challenging a final judgment can be invoked.

The Nature of Retrial (Saishin) in Japanese Civil Procedure

A retrial is not a standard appeal. Ordinary appeals, such as a kōso appeal to a High Court or a jōkoku appeal to the Supreme Court, are pursued before a judgment becomes final and binding (i.e., while the judgment is still "unsettled"). In contrast, an action for retrial is an extraordinary means of attack directed against a judgment that has already become final and binding and has acquired res judicata.

The primary purpose of the retrial system is to provide a pathway for rectifying serious miscarriages of justice that were not, or could not have been, corrected through the normal appellate channels. This might be because the grounds for challenging the judgment (e.g., discovery of forged evidence or perjury) only became apparent after the judgment had already become final and the time for ordinary appeals had expired.

The availability of retrial reflects a fundamental tension in law: the need for legal stability and finality of judgments versus the imperative of achieving substantive justice and correcting egregious errors. Because overturning a final judgment can have significant disruptive effects, the grounds for retrial are strictly defined and narrowly interpreted by the courts.

Statutory Grounds for Retrial: Article 338(1) of the Code of Civil Procedure

The grounds upon which an action for retrial can be based are exhaustively listed in Article 338, paragraph 1, of the Code of Civil Procedure (CCP). A party seeking retrial must demonstrate that their case falls squarely within one of these enumerated categories. Some of the key grounds include:

Unlawful Constitution of the Court (Art. 338(1)(i)): If the court that rendered the original judgment was not constituted in accordance with the law (e.g., incorrect number of judges).
Participation of a Disqualified Judge (Art. 338(1)(ii)): If a judge who was legally barred from participating in the judgment (e.g., due to grounds for recusal such as a conflict of interest) nevertheless took part in rendering the decision.
Defect in Legal Representation or Necessary Authorization (Dairiken no Kenketsu) (Art. 338(1)(iii)): This is a crucial and frequently invoked ground. It covers situations where a party was not properly represented in the original proceedings—for example, if a minor party lacked a legal representative, or if a person purported to act as an attorney or representative without possessing the valid authority or power of attorney to do so.
- Extension by Analogy to Fundamental Lack of Due Process: Significantly, Japanese courts have, through interpretation, extended the spirit of this provision to cover situations where, even if formal representation appeared to be in place, a party was effectively deprived of their fundamental right to participate in the proceedings and present their case. A key area where this has been applied relates to defective service of process that results in a party having no actual notice of the lawsuit.
- The Supreme Court of Japan, in a notable decision on March 20, 2007 (Minshu Vol. 61, No. 2, p. 586), addressed a case where court documents (including the initial complaint) were served via "supplementary service" (hojū sōtatsu) on a co-resident of the defendant. This co-resident, however, had a significant factual conflict of interest with the defendant and failed to pass on the documents, leading to the defendant being unaware of the lawsuit and a default judgment being rendered. The Supreme Court held that even if the supplementary service was deemed formally valid under the procedural rules for service, if the defendant, due to such specific circumstances resulting from the conflict of interest, was in fact deprived of the opportunity to participate in the litigation, this could constitute grounds for retrial by analogy to a defect in legal representation under Article 338(1)(iii). The emphasis was on the substantive denial of the opportunity to be heard, rather than just the formal validity of the service method.
- Earlier, the Supreme Court on September 10, 1992 (Minshu Vol. 46, No. 6, p. 553), had also recognized retrial grounds under this provision where service of the initial complaint on a very young child (who lacked the capacity to understand its significance) was deemed invalid, leading to the defendant parent being unaware of the suit.
Judgment by a Judge Who Committed a Relevant Crime (Art. 338(1)(iv)): If a judge who participated in rendering the judgment is subsequently convicted of a crime concerning that specific case (e.g., bribery in relation to the case). This typically requires that the criminal conviction has become final.
Party's Actions Impaired by Another's Criminal Act (Art. 338(1)(v)): If a party was induced to make an admission or was prevented from presenting a means of offense or defense critical to their case as a direct result of a criminally punishable act committed by the opposing party or a third person (e.g., the opponent's witness committed perjury, or the opponent forged a document that misled the party). This ground also generally requires that the criminal act has been established by a final conviction, or that such a conviction cannot be obtained for reasons other than a lack of evidence (e.g., the perpetrator has died).
Use of Forged or Altered Documentary Evidence (Art. 338(1)(vi)): If a document or other object used as crucial evidence in the original judgment was, in fact, forged or altered. Similar to the above, this usually requires a final criminal conviction related to the forgery or alteration.
Judgment Based on False Testimony, Expert Opinion, etc. (Art. 338(1)(vii)): If the judgment was based on the false testimony of a witness, expert, or interpreter, or on the false statements of a party or legal representative who took an oath. Again, a final conviction for perjury or a similar offense is typically a prerequisite.
Omission of Decisive Evidence (Newly Discovered Evidence) (Art. 338(1)(viii)): If the party seeking retrial has discovered clear and decisive evidence that existed prior to the conclusion of oral argument in the original fact-finding proceedings, but which they were unable to submit at that time through no fault of their own (or without gross negligence). Furthermore, it must be shown that this evidence, if it had been considered, would have clearly led to a different, more favorable judgment for the party seeking retrial. This is one of the more commonly attempted grounds but is applied very strictly by the courts. The evidence must be truly "decisive."
Contradiction with a Prior Binding Judgment (Art. 338(1)(ix)): If the judgment subject to retrial contradicts a prior final and binding judgment that should have been taken into account and which has res judicata effect between the same parties on the same or a prejudicial matter.

For the grounds listed above that involve a criminally punishable act (items (iv) through (vii) of Article 338(1)), paragraph 2 of Article 338 imposes an additional hurdle: an action for retrial based on these grounds can generally only be initiated if the criminal act has been established by a final and binding conviction, or if it is proven that such a conviction cannot be obtained for reasons other than a lack of evidence (for example, if the person who committed the criminal act has died or is outside the jurisdiction). This makes these grounds particularly challenging to invoke successfully.

The Procedure for Initiating a Retrial

Seeking a retrial is not a simple matter of re-arguing the case. It involves a distinct procedural process:

Filing an "Action for Retrial" (Saishin no Uttae): A retrial is sought by filing a new, formal lawsuit (the "action for retrial") with the court that rendered the original judgment which has become final and binding (or with its successor court if the original court no longer exists or has jurisdiction) (CCP Article 340).
Strict Time Limits (Saishin Kikan - CCP Article 342):
- General Period: An action for retrial must be filed within an unextendable period of 30 days from the day on which the party seeking retrial became aware of the grounds for retrial. This is a very short timeframe.
- Absolute Bar: Regardless of when the party became aware of the grounds, an action for retrial generally may not be filed if five years have passed from the day on which the original judgment became final and binding.
- Important Exceptions to Time Limits: Crucially, these 30-day and 5-year time limits do not apply if the asserted ground for retrial is a defect in legal representation or necessary authorization (Article 338(1)(iii)) or that the judgment contradicts a prior binding judgment (Article 338(1)(ix)). This is highly significant for cases like the Supreme Court's 2007 decision concerning defective notice through supplementary service, as it means that a party who was genuinely unaware of the proceedings due to such a fundamental flaw is not barred by these relatively short timeframes from seeking redress once the situation comes to their attention.
Two-Stage Adjudication Process: The court adjudicates an action for retrial in two distinct stages:
- First Stage: Admissibility of the Retrial Action (CCP Articles 345, 346): The court first examines whether the action for retrial itself is permissible. This involves determining if:
  - The asserted grounds for retrial fall within those enumerated in Article 338(1).
  - The action has been filed within the applicable time limits (if any).
  - Other formal requirements for the action have been met.
    If the court finds that the action for retrial is not permissible (e.g., the asserted ground is not a valid one, or the action is time-barred), it will dismiss the action for retrial by means of a judicial ruling (決定 - kettei) (CCP Article 345(2)). This ruling itself is subject to an immediate appeal (sokuji kōkoku). If the court finds the action for retrial to be permissible, it will issue a ruling to commence the retrial (saishin kaishi kettei) (CCP Article 346).
- Second Stage: Retrial on the Merits (CCP Article 348): Only after the ruling to commence retrial has become final and binding does the court proceed to the second stage. Here, the court re-examines the merits of the original case, but only to the extent requested in the action for retrial and justified by the established grounds for retrial. The parties can present arguments and evidence relevant to this re-examination. Following this, the court will render a new judgment which may uphold the original judgment, modify it, or overturn it entirely.

The Principle of Supplementarity of Retrial (Saishin no Hojūsei)

A critical limitation on the availability of retrial is the "principle of supplementarity," articulated in the proviso to Article 338(1) of the CCP. This principle states that a party cannot raise a matter as a ground for retrial if they could have asserted that same matter in an ordinary appeal (such as a kōso or jōkoku appeal) against the original judgment but failed to do so, or if they were aware of the ground during the appeal process but did not raise it.

This means that retrial is generally viewed as a remedy of last resort, available only for serious defects or new discoveries that could not reasonably have been addressed through the standard appellate channels while the judgment was still unsettled. It prevents parties from withholding arguments or evidence during the appeal process only to try and use them later as grounds for an extraordinary attack on the final judgment.

However, there are nuances to this principle. For instance, if a party was entirely unaware of the original judgment itself until after the appeal period had expired (perhaps due to profoundly defective service of process), it would be difficult to argue they "could have" asserted grounds in an appeal they didn't know they needed to file. The Supreme Court decision of September 10, 1992 (Minshu Vol. 46, No. 6, p. 553), suggested that if a party was genuinely unable to appeal because they were not properly notified of the judgment, the principle of supplementarity would not necessarily bar them from seeking retrial once they learned of the judgment and the grounds for challenging its validity. This acknowledges that a party cannot be faulted for not appealing a judgment they had no reasonable opportunity to know about.

Retrial vs. Nullity of Judgment (Hanketsu no Mukō)

It is important to distinguish retrial from the concept of a judgment being entirely "void" (mukō) from its inception. A retrial seeks to revoke or alter a judgment that is, on its face, formally valid and has acquired res judicata, but which is alleged to be substantively flawed due to one of the specific, grave defects listed in Article 338(1).

In contrast, a judgment might be considered inherently void and without any legal effect if it suffers from extremely fundamental defects that negate its very character as a judicial act. Examples could include a judgment rendered against a non-existent person (e.g., someone deceased long before the suit began, with no heir participation), a "judgment" issued by an entity completely lacking judicial authority, or a judgment obtained through such a profound violation of fundamental due process that it cannot be recognized by the legal system. A truly void judgment does not technically require a retrial to be disregarded; its invalidity could, in theory, be asserted in any subsequent proceeding where its effect is at issue (e.g., as a defense to an attempt to enforce it). However, the threshold for a court to declare a formally rendered and finalized judgment as entirely void (as opposed to merely being voidable through the retrial process) is exceptionally high in Japanese practice, reserved for only the most extreme and manifest defects.

Conclusion

The saishin (retrial) system in Japanese civil procedure serves as an extraordinary but vital safeguard against irretrievable miscarriages of justice that may have occurred in judgments that have already become final and binding. It reflects the legal system's attempt to balance the strong societal and legal interest in the finality and stability of judicial decisions with the equally important imperative to correct fundamental errors and ensure substantive justice.

The grounds for seeking a retrial are narrowly defined by statute and are strictly interpreted by the courts. The procedural requirements, including stringent time limits for most grounds, further underscore the exceptional nature of this remedy. However, judicial interpretations, particularly concerning defects in legal representation and, by analogy, fundamental failures of procedural due process such as the denial of an opportunity to be heard due to flawed service of process, have shown a degree of flexibility in ensuring that the doors of justice are not entirely closed when a party has been substantively deprived of their right to a fair hearing. Given the demanding nature of this remedy, parties who believe they may have grounds for retrial must act with extreme diligence and seek expert legal counsel to navigate its complex requirements.