Wis. Stat. § 891.41
In order for a putative biological father to have the necessary foundation for a constitutionally protected liberty interest in his putative paternity, he would have to have taken affirmative steps to assume his parental responsibilities for the child. Randy A.J. v. Norma I.J., 2004 WI 41, 270 Wis. 2d 384, 677 N.W.2d 630, 02-0469. A genetic test showing another man to be the natural father rebuts the presumption under s. 767.48(1m) [now s. 767.84(1m)] and sub. (1) that the spouse of the child's mother is the father, but equitable estoppel may be employed to preclude rebutting the presumption. The issue is whether the actions and inactions of the parties advocating the rebuttal of the marital presumption were so unfair as to preclude them from overcoming the public's interest in the marital presumption based on the results of genetic tests. Randy A.J. v. Norma I.J., 2004 WI 41, 270 Wis. 2d 384, 677 N.W.2d 630, 02-0469. The presumption that the mother's husband is the child's father does not violate a putative father's due process rights. Michael H. v. Gerald D., 491 U.S. 110, 105 L. Ed. 2d 91 (1989). If a child is conceived subsequent to the entry of a decree of legal separation, there is no presumption of paternity. Schoenfeld v. Apfel, 237 F.3d 788 (2001). As I See It: Out of Sync: Assistive Reproductive Technology & Parentage Law. Walsh. Wis. Law. May 2017.