At common law, a child born to the wife during the marriage is presumed to be the husband's child, as determined by law. This well-settled concept is the "presumption of lawful paternity", and assigns to the husband complete rights, duties and obligations as to the child, regardless of whether he is the biological parent or not. The presumption, however, can be rebutted by evidence to the contrary, at least before a court issues a formal adjudication of paternity in the husband's favor, or a duty of support is established by a decree of divorce, annulment, or legal separation. Jurisdictions differ widely on whether, when, and under what circumstances a judgment establishing paternity or a support obligation founded on the presumption can be set aside on the grounds that the husband was not in fact the father.

In the case of an unwed mother a man may come forward and accept the paternity of the child, the mother may petition the court for a determination if she can identify the likely candidate(s) or paternity can be determined by estoppel over time.

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