If a DNA Test Denies Paternity, What Happens to the Legal Parent-Child Relationship?

Rewritten on: March 3, 2025

Even if a DNA test denies paternity, the legal parent-child relationship may not be immediately dissolved. This article explains in detail the legal procedures and deadlines, including the action to deny legitimacy and the action to confirm non-existence of a parent-child relationship.

What you should know when conducting a father-child DNA test

What happens to the legal parent-child relationship if a DNA test denies paternity? For a man, whether a child is biologically his own is an extremely important matter. In recent years, dramatic advances in DNA testing technology have made it possible to determine biological parent-child relationships with an accuracy of 99.99% or higher. However, biological facts and legal parent-child relationships do not necessarily coincide.

This time, we will explain in detail what you need to know about the laws and procedures surrounding father-child DNA testing, drawing on case law and provisions of the Civil Code.

First, to state the conclusion: even if a test result unfortunately denies a father-child relationship, the legal parent-child relationship may continue regardless of whether the parents are divorced. In other words, a person may not be a biological parent yet still be a legal parent [ref:1]. This is a point that surprises many people, but Japan's Civil Code has mechanisms in place to protect a child's legal stability, and a DNA test result alone does not automatically dissolve the parent-child relationship.

What is the presumption of legitimacy system

Japan's Civil Code has a system called the "presumption of legitimacy." This is a provision stating that a child born to a married couple is legally presumed to be the husband's child (Article 772 of the Civil Code). Specifically, it provides as follows.

• A child conceived by the wife during marriage is presumed to be the husband's child
• A child born more than 200 days after the date of marriage is presumed to have been conceived during the marriage
• A child born within 300 days of the dissolution (divorce) or annulment of marriage is presumed to have been conceived during the marriage

This presumption of legitimacy system was established to stabilize a child's status at an early stage, and is a legal framework that prioritizes the child's welfare above all else. Therefore, even if a biological father-child relationship is denied by a DNA test, for a child to whom the presumption of legitimacy applies, the parent-child relationship cannot be dissolved without going through the prescribed legal procedures [ref:2].

The Supreme Court ruling of July 17, 2014 (Heisei 26)

An extremely important precedent for understanding the relationship between the presumption of legitimacy and DNA testing is the Supreme Court ruling of July 17, 2014 [ref:1].

In this case, scientific evidence in the form of a DNA test made clear that there was no biological father-child relationship between the husband and the child, and the husband had already divorced the wife, they had separated, and the child was being raised by the wife. Nevertheless, the Supreme Court did not uphold the action to confirm the non-existence of a parent-child relationship.

This means that the relationship built up over the years of daily life as the husband's child was given greater weight than the DNA test result. The court held that the purpose of the presumption of legitimacy system is to protect the legal stability of a child's status, and that even though advances in science and technology now make it possible to confirm a biological father-child relationship with high precision, it is not appropriate to immediately deny the legal parent-child relationship on that basis alone [ref:3].

Underlying this is the idea that if a child who has been raised as one's own suddenly has that father-child relationship declared never to have existed, the disadvantages to the child—psychological, financial, and otherwise—would be too great. Specifically, this is because it could fundamentally undermine the child's basis for living, including changes to the family register, the loss of the duty of support, and the loss of inheritance rights.

Action to deny legitimacy ― a legal method to deny a father-child relationship

So, is it impossible to overturn a father-child relationship? There is a legal method called the "action to deny legitimacy" by which a father can have it legally recognized that a child is not his own.

An action to deny legitimacy is a legal procedure to deny that a child presumed to be a legitimate child (a child of a married couple) is "not my child." When pursuing this procedure, a DNA test result serves as extremely strong evidence.

Important points about the action to deny legitimacy

Below are particularly important points to note regarding the action to deny legitimacy.

1. Who may file: In principle, the father (husband) files the action. Note that under the 2022 (Reiwa 4) Civil Code revision (effective April 1, 2024), the child and the mother are now also permitted to file [ref:4].
2. Filing period: Under the pre-revision Civil Code, the period was within one year from when the child's birth became known. After the revision, the period has been extended: for the husband, within three years from when he learns of the child's birth; for the child, within three years from the child's own birth; and for the mother, within three years from the child's birth [ref:4].
3. Jurisdiction: The action is filed with the family court that has jurisdiction over the child's place of residence.
4. DNA testing as evidence: A DNA test result is extremely powerful evidence in an action to deny legitimacy, but for it to be recognized as a legal test, strict procedures are required, including proper sample collection procedures and the presence of a third party.

In other words, once the prescribed deadline has passed, an action to deny legitimacy can no longer be filed even if a DNA test shows there is no parent-child relationship. Because legal stability in the child's social life is prioritized, the system is designed so that filing is only possible within a limited period.

Action to confirm non-existence of a parent-child relationship ― another legal remedy

Also, when it is clear that the wife could not have become pregnant by the husband (for example, because the husband was away on a long business trip or the couple was separated and had no sexual relations with the child's mother), an "action to confirm non-existence of a parent-child relationship" can be filed [ref:5]. This type of action is used in cases where the presumption of legitimacy does not apply, that is, cases falling under "a child not covered by the presumption."

Differences between the action to deny legitimacy and the action to confirm non-existence of a parent-child relationship

Unlike the action to deny legitimacy, the action to confirm non-existence of a parent-child relationship has no time limit for filing. Also, not only the father but the mother and the child can also bring the action. However, as shown by the 2014 Supreme Court ruling discussed above, this type of action cannot be used in cases where the presumption of legitimacy applies, so its scope of application is limited and caution is required [ref:3].

Making a DNA test legally valid

To submit a DNA test result as evidence in a court case or mediation, it is important that the test be conducted using the proper procedure as a "legal test (court-use test)." A private test conducted on one's own may be used as reference material in some cases, but its reliability as evidence and admissibility may be contested.

To be recognized as a legal test, the following requirements are generally required.

• Samples must be collected in the presence of a third party (such as an attorney)
• Strict identity verification of the test subjects must be carried out
• A chain of custody must be secured to prove that no tampering occurred from sample collection through delivery to the testing institution
• The testing institution must meet internationally recognized quality standards
• The test report must clearly state the examiner's signature and the testing institution's certification information

seeDNA partners with more than 150 law firms nationwide and conducts highly reliable legal DNA tests in the presence of attorneys who are legal professionals. The test results can be used in legal proceedings such as court cases and mediation.

Changes to the legitimacy denial system under the 2022 (Reiwa 4) Civil Code revision

The revised Civil Code, enacted in 2022 (Reiwa 4) and effective from April 1, 2024 (Reiwa 6), made major changes to the legitimacy denial system [ref:4]. The main changes are as follows.

• Expansion of who may deny legitimacy: Previously, only the husband could file an action to deny legitimacy; now the child and the mother may also file.
• Extension of the filing period: The previous period of "one year from learning of the birth" has been extended to "three years."
• Revision of the presumption of legitimacy after remarriage: The waiting period before a woman may remarry has been abolished, and a new provision has been established presuming that if the mother has remarried by the time of the child's birth, the child is presumed to be the child of the new husband.

With this revision, it has become possible for the child and the mother themselves to seek a denial of legitimacy, expanding the system in a direction that more appropriately protects the child's interests. Those considering a DNA test are advised to consider the legal response with these revisions in mind.

Summary

This time, we explained from a legal perspective what happens to the parent-child relationship when a DNA test denies paternity. DNA testing is a scientific method that can determine a biological parent-child relationship with extremely high accuracy, but dissolving the legal parent-child relationship requires a separate, appropriate legal procedure. The action to deny legitimacy has a filing deadline, and the action to confirm non-existence of a parent-child relationship can only be used in limited cases.

Settling a parent-child relationship through litigation or mediation is difficult for both parties, but sometimes uncovering the truth allows people to move forward.

seeDNA accepts applications for legal testing for all kinship tests. We partner with more than 150 law firms nationwide, allowing you to receive a reliable DNA test in the presence of an attorney who is a legal professional. The test results can also be used in court proceedings and mediation.

If you are considering a legal response regarding confirmation of a blood relationship, please consult seeDNA, a domestic genetic testing institution.

Contact Us
DNA Testing Cost and Turnaround Time
About Ultra-High-Accuracy Paternity DNA Testing

Frequently Asked Questions

Q1. If a DNA test denies a father-child relationship, is the legal parent-child relationship automatically dissolved as well?

A. No, it is not automatically dissolved. A DNA test only proves a biological fact; to dissolve the legal parent-child relationship, a separate legal procedure such as an action to deny legitimacy or an action to confirm non-existence of a parent-child relationship must be carried out. In the 2014 Supreme Court ruling, there was a case in which the legal parent-child relationship was maintained even though the DNA test denied the father-child relationship [ref:1].

Q2. By when must an action to deny legitimacy be filed?

A. Under the revised Civil Code, effective April 1, 2024, the husband must file within three years of learning of the child's birth, the child must file within three years of their own birth, and the mother must file within three years of the child's birth. If this deadline passes, an action to deny legitimacy can no longer be filed even if a DNA test proves there is no parent-child relationship [ref:4].

Q3. What is the difference between an action to deny legitimacy and an action to confirm non-existence of a parent-child relationship?

A. An action to deny legitimacy is a procedure used for a child to whom the presumption of legitimacy applies, and it has a filing deadline. An action to confirm non-existence of a parent-child relationship, on the other hand, is a procedure used for a child to whom the presumption of legitimacy does not apply (such as when the husband was away for a long period and sexual relations were impossible); it has no time limit and can be filed by the father, mother, or child [ref:5].

Q4. How can a DNA test result be used as evidence in court?

A. To be used as evidence in court, the test must be conducted as a legal test (court-use test). Samples must be collected in the presence of a third party such as an attorney, and identity verification and chain of custody must be secured. seeDNA partners with more than 150 law firms nationwide and supports legal testing.

Q5. How did the legitimacy denial system change under the 2022 Civil Code revision?

A. There were three major changes: (1) the right to deny legitimacy was expanded from the husband alone to include the child and the mother; (2) the period for exercising the right to deny legitimacy was extended from one year to three years; and (3) the waiting period before a woman may remarry was abolished, and the presumption of legitimacy after remarriage was revised. These changes improved the system to better protect the child's interests [ref:4].

Q6. How accurate is DNA testing?

A. With current DNA testing technology, when a father-child relationship exists, it is affirmed with a probability of 99.99% or higher, and when it does not exist, it is denied with 100% certainty. seeDNA offers ultra-high-accuracy paternity DNA testing and delivers highly reliable results.

[References]