However, there is a court case out in AZ that says that the courts can consider "the best interests of the child" in making a decision about who is the "legal" father, even though a DNA test may say the father is not the biological father.
Stephenson v. Nastro, 967 P.2d 616 (1998
The Arizona Supreme Court determined that, under the statutes, when a parent raises the paternity issue, it is not necessary to hold a “best interests of the child” hearing before ordering genetic tests. “Best interests” are to be considered only after testing in determining custody and visitation issues. However, the court found that the statutes also establish that a voluntary acknowledgment of paternity is valid and binding until proven otherwise. After 60 days, it can be attacked only for “fraud, duress, or material mistake of fact” and the challenger has the burden of proof. Here, there should have been a Rule 60(C) hearing to determine whether these statutory requirements had been met. Only if
the mother provides clear and convincing evidence that fraud, duress or material mistake of fact has occurred can she too request genetic tests. If she does not meet this burden, tests are inappropriate.
So the take away here is that even if a father is not the biological father, the courts can rule that he is still the "legal" father if it is in the child's best interests..