TOPEKA, Kan. (AP) — The state of Kansas is trying to force a man who donated sperm to a lesbian couple to pay child support, arguing that the agreement he and the women signed releasing him from all parental duties was invalid because they didn't go through a doctor.

Under Kansas law, a doctor's involvement shields a man from being held responsible for a child conceived through artificial insemination. At least 10 other states have similar laws, including California, Illinois and Missouri, according to the Kansas Department for Children and Families.

William Marotta and the couple he helped have a daughter didn't go through a doctor, so the department is asking a state court to hold him responsible for about $6,000 that the child's biological mother received through public assistance — as well as future child support.

The department also asked the court to appoint an attorney to represent the now 3-year-old girl, independently of her mother.

Marotta is asking that the case be dismissed, arguing that he is not the child's legal father. A hearing is set for Tuesday.

Department spokeswoman Angela de Rocha said Wednesday that when a single mother seeks benefits for a child, the department routinely tries to determine the child's paternity and require the father to make support payments to lessen the potential cost to taxpayers.

She argued that the law regarding artificial insemination is an incentive for donors and prospective mothers to work with a doctor.

"I believe that is the intent of the law, so that we don't end up with these ambiguous situations," she told The Associated Press.

Marotta, a 46-year-old Topeka resident, answered an ad on Craigslist in 2009 from Angela Bauer and Jennifer Schreiner, a local couple who said they were seeking a sperm donor.

After exchanging emails and meeting, Marotta and the couple signed an agreement in which the women agreed to "hold him harmless" financially. It also said the child's birth certificate would not list a father.

But the state agency argues the agreement isn't valid, because instead of working with a doctor, Marotta agreed to drop off containers with his sperm at the couple's home, according to prepared court documents the department gave to the AP late Wednesday.

The women handled the artificial insemination themselves using a syringe, and Schreiner eventually became pregnant, according to the documents. The couple broke up in 2010, and last year, Schreiner received public assistance from the state to help care for the girl.

"My ex-partner and I wanted to have a baby," Schreiner said in a written statement to the department in January 2012, also included in the department's latest filing. "We were a gay couple so we had a sperm donor."

Marotta told The Topeka-Capital Journal that he is "a little scared about where this is going to go, primarily for financial reasons." His attorney didn't return a phone message Wednesday from the AP, and there was no listing for his home phone number in Topeka.

Phone numbers listed for Schreiner and Bauer were either incorrect or out of service, and Schreiner did not respond to a message sent by Facebook.

The department first filed a petition against Marotta in Shawnee County District Court in October, asking that he be required to reimburse the state for the benefits and make future child support payments.

Along with the 1994 law regarding artificial insemination, the department cited a 2007 Kansas Supreme Court ruling. In that case, the court decided that a sperm donor who works through a licensed physician can't legally be considered a child's father — and doesn't have the right to visit or help raise the child — absent a formal, written agreement.

However, that case involved a sperm donor who was seeking access to a child but had only an informal, unwritten agreement with the child's mother. Marotta's attorneys contend the state is reading it incorrectly.

Still, Linda Elrod, a law professor and director of Washburn University's Children and Family Law program, said the law seems clear: Sperm donors who don't want to be held liable for child support need to work with a doctor.

"Other than that, the general rule is strict liability for sperm," said Elrod, who filed a friend-of-the-court brief in the Supreme Court case.