paternity suit

Definition from Nolo’s Plain-English Law Dictionary

A lawsuit to determine the identity of the father of a child born outside of marriage. A paternity suit may be brought either by the mother or by the father himself if the mother is denying his paternity, and is usually proved by genetic testing. Once paternity is established, the father has all the rights and obligations of parenthood, including the duty to support the child and the right to petition for custody or visitation.

Definition provided by Nolo’s Plain-English Law Dictionary.