California’s Supreme Court is expected to decide this summer what criteria makes a person a parent in a homosexual relationship and if that criteria is based on biology, legal standards or the role a person lived in that relationship, that is, if a person acted like a parent.

The state Supreme Court in San Francisco heard three cases May 24, all involving the parental rights of homosexals once the couple has split up. A ruling is expected in the coming months.

With heterosexual couples, decisions regarding custody and child support are generally simple because the biological criteria is usually present. This is not the case with homosexual couples.

A report in USA Today described the three cases. In one case, Elisa Maria B. and Emily B. decided they wanted children. Emily became pregnant by a sperm donor and gave birth to twins in 1998; one had Down Syndrome. The couple decided Emily would stay home and care for the children while Elisa Maria worked to support them.

The couple split 18 months later, and Elisa cut off financial support, arguing that she was not the children’s biological father. The case made its way to the Supreme Court, with lower courts once ruling in favor of Emily and once ruling in favor of Elisa Maria.

In the second case, K.M. v. E.G., a fertilized egg from K.M. was implanted in E.G., who had twins in 1996. The couple split in 2002, and E.G. denied K.M. access to the children. She cited a waiver of parental rights K.M. signed when she donated her egg. At the state Supreme Court, however, K.M.'s lawyers argued that how the couple lived — both acting as parents for six years — should trump the waiver.

In the third case, Kristine H. v. Lisa R., Kristine had a daughter through artificial insemination. Before the girl was born, she received a court judgment that Lisa was the legal “father” and that both partners were the parents.

The couple split nearly three years later, and Kristine asked the court to void the judgment and rule that Lisa had no visitation rights. An appeals court agreed with her. But Lisa’s attorney’s argued before the state Supreme Court that Lisa's behavior as a parent entitled her to visitation.

Family law professor Ed Stein of Cardozo Law School in New York City said these cases underscore that the law is increasingly defining relationships according to their functionality, or the roles people take on in relationships. “That's a direction in which the law, generally speaking, is headed,” he told USA Today.

Similar legal cases are being heard in Utah, Georgia and Washington state. Courts in New York, Vermont and Pennsylvania have already ruled that both partners of same-sex couples who split may be considered parents.