Almost everyone has seen at least one episode of the Maury Povich Show or Jerry Springer during which the climactic moment is the announcement of whether or not the hero (or sometimes villain) of the episode is or is NOT the father. This scene is usually followed by the gentleman in question celebrating a result he expected accompanied by the plaintive sobs of the mother who was SURE that he was the father and promised he was the ONLY ONE. Despite what we see on television, challenges to paternity in Pennsylvania court are usually not as dramatic as one might think.
The presumption of paternity in Allegheny County has evolved over the years. Originally, paternity was presumed if a man and woman were married and the woman gave birth to a child. Unless the man had no access to the woman or had been proven to be sterile, the child would be legally presumed to be his. Because of this presumption, no third party could assert their own claim of paternity to the child.
In Pennsylvania, paternity by estopple is a doctrine that functions to prohibit a person from denying paternity due to his conduct. Estopple can also be used to prevent a third party from making a claim that he is actually the father. The doctrine of estopple centers around the idea that the best interest of the child is the most important factor when it comes to paternity and custody law. The court does not want to force the child to start a relationship with a stranger instead of continuing the relationship with the father the child has know all along.
Paternity is often a very important issue in family law cases. Most people have watched episodes of "Jerry Springer" or "Maury" where whole shows are based on revealing paternity test results to a couple, which either turns out to be good news, or a not-so-great revelation that causes fighting on the set (cue the Bodyguards!) However, in the family court realm, paternity is an issue that is taken much more seriously than may be portrayed on television.