Is it right to force a man who learns that he is not the biological father of a child to support the child and to jail him if he doesn't? Last week, the Judiciary Committee of the Colorado Senate said no, at least not if the child is under age 5. If that state's House and governor agree, Colorado will join a handful of states that have acted to protect those who have come to be called "duped dads."

Several states allow parental responsibilities to be abolished once paternity is ruled out, no matter how old the child is. Prove that the kid isn't yours, and you're off the hook.

New Hampshire law is unclear on the issue. It is in the best interest of children, most of all, that lawmakers clarify the situation.

Other legislatures are debating what the appropriate time limit should be for challenging paternity. After some point, the harm to children who have developed an emotional bond with the men they thought were their fathers and who require financial support may be too great to revoke paternity.

It's hard to say how many false fathers there are. Estimates vary widely, but a recent study of 65 analyses of paternity cited by The New York Times placed the percentage of mistaken or misled fathers at 1.7 to 3.7 percent. Studies suggest that men who suspect they might not have fathered a child considered to be theirs are right about 30 percent of the time.

The reform of federal welfare laws has made for aggressive prosecution and pursuit of deadbeat dads. New Hampshire law allows the state to attach wages, place liens on property, suspend the licenses of parents who owe child support payments and jail them. The federal government can deny a passport to a parent in arrears.

Once paternity has been established in New Hampshire, the responsibilities that come with it can be removed only by a court. The law gives judges broad discretion in the matter, and their views could differ.

In a 2003 opinion, the state Supreme Court lifted the child support responsibilities of a man who wrongly assumed he had fathered a child, but it denied his request that the state reimburse him for back child support payments. Payment, the court said, would have to be collected from the biological father. The mother, if she deliberately misled the man, could be sued for fraud, the court said.

Testing to establish paternity can now be performed relatively cheaply and, if a child's hair sample is used, even without the knowledge of both parents.

The increasing use of genetic screening and other medical tests also means that more people are learning the truth inadvertently. Knowledge of wrongful paternity can present hospitals with an ethical dilemma. Tell, don't tell, or lie and say the test results were inconclusive.

There is far more to fatherhood than fertilization. At some point, a man who treats a child as his own is that child's father in what may be the most important way of all. The bond becomes bigger than biology.

The question of when to disestablish paternity is not an easy one, but uncertainty about the law benefits no one. Lawmakers should begin to debate the proper balance between the rights of mistaken fathers and the needs of children who would be harmed if the men they've called Dad can sever the relationship.