What If a Married Woman Has a Child With Someone Other Than Her Husband?
Wisconsin law generally presumes that a husband is the father of a child conceived or born during the marriage. That presumption can create a legal problem when the spouses are separated, the husband is not the biological father, and another man is believed to be the child's biological father.
The marital presumption
Under Wis. Stat. section 891.41, a man is presumed to be the natural father of a child when he and the child's mother are or have been married and the child is conceived or born after the marriage and before a decree of legal separation, annulment, or divorce. In practical terms, separation by itself does not automatically eliminate the presumption.
How can the presumption be rebutted?
Wisconsin law expressly allows the marital presumption to be rebutted by qualifying genetic-test results showing that another man is not excluded as the father and that the statistical probability of his parentage is at least 99 percent. A paternity action may be brought under Wis. Stat. section 767.80 for the purpose of determining paternity or rebutting an existing presumption.
Why the court still matters even when everyone agrees
Even when the husband, mother, and biological father all agree about biological parentage, the legal presumption should not simply be ignored. A court order can formally determine who is and is not the legal father, address the child's legal status, and permit appropriate changes to vital records. The court may also need to address custody, placement, and child support once paternity is established.
What role can genetic testing play?
Genetic testing is often the central evidence in these cases. Under Wis. Stat. section 767.84, a 99 percent or greater probability of paternity creates a rebuttable presumption for the tested alleged father, while test results excluding a man are conclusive evidence of nonpaternity as to that man. Where the marital presumption exists, section 891.41 specifically addresses how qualifying test results involving another man can rebut that presumption.
What may the court consider beyond biology?
Paternity law is not only about laboratory results. Depending on the procedural posture, the court may need to protect the child's legal interests, determine whether a guardian ad litem is required, and ensure that the correct parties receive notice. In some cases, an existing family relationship, prior legal determinations, or another parentage presumption may make the procedure more complicated.
What happens after paternity is resolved?
Once legal paternity is determined, the court may address legal custody, physical placement, and child support. A paternity judgment under Wis. Stat. section 767.89 includes an adjudication of paternity and may include custody, placement, and support orders. Those decisions are governed by the same best-interest principles that apply in other Wisconsin family cases.
Practical point
If a child is born during a marriage but another man is believed to be the biological father, it is usually better to address the legal presumption directly rather than assume that biological facts alone will change legal parentage. A properly handled paternity proceeding can prevent later disputes involving support, custody, inheritance, medical decision-making, and vital records.
Official Wisconsin resources
Wis. Stat. section 891.41 - Presumption of paternity based on marriage: https://law.justia.com/codes/wisconsin/chapter-891/section-891-41/
Wis. Stat. section 767.80 - Determination of paternity: https://law.justia.com/codes/wisconsin/chapter-767/section-767-80/
Wis. Stat. section 767.84 - Genetic testing: https://law.justia.com/codes/wisconsin/chapter-767/section-767-84/
General information only. This page is not legal advice, and the application of Wisconsin law depends on the facts of each case.