Justice Brennan, joined by Justices Marshall and Blackmun, criticized the plurality’s method of defining liberty at the narrowest historically available level. History and tradition, he argued, can be disputed and selectively framed; treating a practice’s historical nonrecognition as dispositive turns the Due Process Clause into a shield only for interests already protected by majorities.
The proper starting point, in his view, was the well-established constitutional interest in parent-child relationships. Under Stanley, Caban, Quilloin, and Lehr, biology alone does not suffice, but a biological father who develops a substantial relationship and accepts parental responsibility has a protected liberty interest.
Michael satisfied that standard. He was almost certainly Victoria’s biological father, lived with her at times, financially supported her, held her out as his child, and persistently sought to maintain their relationship. The fact that Carole was married to Gerald should affect the State’s justification for limiting Michael’s rights, not erase the liberty interest in the first place.
Justice Brennan regarded § 621 as a conclusive presumption that cut off Michael and Victoria’s protected relationship without any meaningful opportunity to prove paternity. Calling the provision a substantive rule did not change its operation: California made factual paternity relevant in other circumstances but categorically barred Michael from proving it here.
California’s interests in marital privacy and family stability did not justify denying even a paternity hearing. Modern blood testing could establish paternity with little intrusion, and a hearing would not automatically give Michael custody or visitation; any later decision about visitation could still turn on Victoria’s best interests.