He was a 15-year-old kid with all the usual teenage sexual passions.

She was his neighbor--a 34-year-old mom, later convicted of statutory rape for engaging him in a romantic tryst that resulted in her getting pregnant.

But in a case that sets the term "deadbeat dad" on its ear, a California appeals court has ruled that the young man from San Luis Obispo, identified only as "Nathaniel J." in court records, is responsible for paying child support for the baby born of the illegal union.

The ruling by the 2nd District Court of Appeal in Los Angeles--the first decision of its kind in California--leads to a number of sticky societal questions, ranging from whether girls and boys should be treated differently in cases of statutory rape to the fairness of government's increasingly aggressive pursuit of child-support payments.

"This is a really bizarre case," said Mary Ann Mason, a social-welfare professor at the University of California at Berkeley who specializes in societal legal issues. "It seems unfair that he was taken advantage of, and then he gets prosecuted for child support. He's considered a victim on one hand and a perpetrator on the other."

County and state authorities, rather than the mother, have pursued the case, seeking compensation for welfare payments the infant girl has been receiving since her birth in January 1995.

Attorneys from the state attorney general's office, which represented the state in the appeal, say the teenager should be responsible for the child because he indicated he was a willing sexual partner.

"Our point of view is that the newborn is the victim in these matters," said Carol Ann White, a lawyer who heads the attorney general's child-support-enforcement unit. "No matter what the circumstances of their conception, babies deserve to have two parents.

"And this was a consensual relationship," she added.

The youth, now 18, won't be required to pay until he has income, said Deputy Atty. Gen. Mary Roth, who handled the case.

"Say he makes $800 a month working at Burger King," Roth said. "He'll probably be expected to pay $200 a month to reimburse" the welfare program.

Under state law, the boy's parents are not responsible for child support for their granddaughter.

The case began in 1994, with a two-week affair between the boy and the unmarried woman, listed in court records as Ricci Jones.

According to court records, Jones and the teenager discussed having sex in advance and made a clear decision to do it. They had intercourse approximately five times, in what the boy later told police investigators was "a mutually agreeable act."

Neither Jones nor the teenager could be reached for comment.

The matter did not become a court case until after their daughter was born on Jan. 20, 1995, and Jones began receiving welfare on the daughter's behalf. Under federal guidelines, counties must make an effort to determine the identity of the father of any child on welfare and collect child support from him to offset the welfare payments.

That's exactly what San Luis Obispo County did.

As soon as county officials realized the baby's father was a minor, they filed statutory-rape charges against Jones, which resulted in a conviction but no jail time. Almost simultaneously, they sought to have the young father registered as being responsible for child support.

After being ordered to pay by Superior Court, "Nathaniel J." and his parents appealed the decision, arguing that a child who was the victim of sexual exploitation by an adult should not be penalized for the consequences of the exploitation.

But the appeals court disagreed.

"Victims have rights. Here, the victim also has responsibilities," said the opinion, written by Judge Arthur Gilbert. He cited cases from other states in which minors were deemed responsible for child support if they had consented to sex with an adult.

"We conclude he is liable for child support."

Clearly, said Roth, if a teenage boy got a teenage girl pregnant, no one would question the state for holding him responsible. She said the teenager's testimony made it clear he had known what he was doing and agreed to it.

"I guess he thought he was a man then," she said. "Now, he prefers to be considered a child."

But Fred Hayward, founder of the Sacramento-based group Men's Rights Inc., said the court was setting a horrible double standard.

"This is victimizing the victim," he said. "The law is based on the premise that a 15-year-old is too young to give his consent to anything. Yet he gets a 34-year-old woman pregnant, and suddenly he's old enough to be responsible."

Professor Mason said the case adds several twists to traditional family law.

"This shows two new directions in the law that are just now coming into play," she said. "One is that the state is going after young dads--and it isn't necessarily using much discretion. The other is that women are being prosecuted for statutory rape, which never would have happened two or three years ago."

Until 1994, the state's statutory-rape law didn't even apply to boys; only adults who had sex with young girls could be prosecuted. The legislature changed the law two years ago, but prosecutions of women are rare, Mason said.