(Adds details from cross-examination)
By James B. Kelleher
DETROIT, Feb 25 (Reuters) - Michigan's ban on gay marriage perpetuates discrimination and should be overturned, an attorney representing a lesbian couple argued on Tuesday at the start of the latest in a series of legal challenges to U.S. laws banning same-sex unions.
But the state countered in U.S. District Court in Detroit that its law barring gay nuptials represented the "will of the people" who voted it into Michigan's constitution a decade ago.
U.S. attitudes and laws on same-sex unions have changed markedly over the past decade, with 17 states and the District of Columbia now allowing gay marriage, first made legal in Massachusetts in 2003.
In opposing gay marriage, the state has focused on the well-being of children, arguing that their interests are best served by having both a father and a mother, a position dismissed by gay rights advocates and their allies.
"No other group in society has to pass a parental competency test before they're allowed to marry," attorney Carole Stanyar, who represents the couple, said in an opening statement. "We would like this to be the last trial in America where same-sex couples have to defend themselves."
Assistant Michigan Attorney General Kristin Heyse defended the ban and urged U.S. District Judge Bernard Friedman to leave it in place.
"This case is about one thing: the will of the people," Heyse said. "This was not the whim of a few."
Several dozen peaceful demonstrators marched in front of the courthouse as lawyers gathered for the trial. Some supporters of the law carried signs that read "We Support Traditional Marriage - One Man, One Woman," while opponents held signs urging the court to overturn the ban.
April DeBoer and Jayne Rowse, who live in the Detroit suburb of Hazel Park, are asking Friedman to overturn a state law that prevents them from adopting each other's children in addition to taking on the state ban on gay marriage, which was approved as a constitutional amendment by voters in 2004.
The couple, both nurses, brought their lawsuit in 2012. Friedman waited for the U.S. Supreme Court to rule on cases that were pending before proceeding with the Michigan case.
NEEDS OF CHILDREN
In June, the U.S. Supreme Court threw out a key part of the Defense of Marriage Act, which denied same-sex couples federal benefits that are available to heterosexual couples. A separate decision allowed same-sex marriage in California.
Friedman ordered the trial on the Michigan case in October. Several courts around the country have struck down same-sex marriage bans since then.
Michigan's attorney general has said in court papers that the marriage amendment voters adopted is rationally related to legitimate state interests and that marriage between one man and one woman was "uniquely suited to the rearing of children."
David Brodzinsky, an expert on child welfare, adoptions and foster care who testified for the couple, disputed the idea that children needed a male and female parent.
"Children of gay and lesbian individuals show no discernible differences in outcomes," Brodzinsky said. "The parenting qualities of gays and lesbians are no different from heterosexual couples."
Brodzinsky said the gender or sexual orientation of parents might influence parenting styles but not in a way that would impact the well-being of children. The stability of parents, regardless of their gender and orientation, is much more important, he said.
Under cross-examination by Michigan Assistant Attorney General Joseph Potchen, Brodzinsky acknowledged that studies on the stability of same-sex couples were mixed, with some showing a higher breakup rate among gay couples.
The trial resumes on Wednesday morning and is expected to last about two weeks. The state is expected to begin presenting its defense of the ban next week. (Additional reporting by David Bailey in Minneapolis; Editing by Scott Malone and Jonathan Oatis)