DNA Forensics is a Great Thing,

but it also can create havoc in family disputes, including divorce and child support:

In an age of DNA, when biological relationships can be identified with certainty, it can seem absurd to hew so closely to a centuries-old idea of paternity. And yet basing paternity decisions solely on genetics places the nonbiological father’s welfare above the child’s. Phil Reilly, a lawyer who is also a clinical geneticist, has been wrestling with the policy implications of DNA testing for years, and even he is stumped about how society should manage the problem that men like Mike face. “We’re at a point in our society where the DNA molecule is ascendant, and it’s very much in the public’s consciousness that this is a powerful way to identify relationships,” Reilly says. “Yet at the same time, more people than ever are adopting children, showing that parents can very much love a child who is not their own. The difference here for many men is the combination of hurt and rage over the deceit, the fact that they’re twice beaten. I can see both sides of this argument. As a nation, we’re still in search of what the most ethical policy should be. Every solution is imperfect.”

Once a man has been deemed a father, either because of marriage or because he has acknowledged paternity (by agreeing to be on the birth certificate, say, or paying child support), most state courts say he cannot then abandon that child — no matter what a DNA test subsequently reveals. In Pennsylvania and many other states, the only way a nonbiological father can rebut his legal status as father is if he can prove he was tricked into the role — a showing of fraud — and can demonstrate that upon learning the truth, he immediately stopped acting as the child’s father. In 2003, a Pennsylvania appellate court bluntly applauded William Doran — who had been by all accounts a loving father to his 11-year-old son — for cutting off ties with the boy once DNA showed they were not related. The judges found that Doran had been tricked by his former wife into believing he was the father of their son, and he was allowed to abandon all paternal obligations.

If a man is supporting a child--regardless of whether the child is biologically "his"--he should continued to support that child.

It's about the child's welfare, not about the man's convenience.