SAN FRANCISCO (Reuters) - In surprising testimony, a witness called to defend California's gay marriage ban testified on Tuesday that legalizing same-sex matrimony would "improve the well-being of gay and lesbian households and their children."
The landmark case in U.S. district court in San Francisco seeks to overturn California's ban on gay marriage, known as Proposition 8, approved by voters in 2008.
The final defense witness, David Blankenhorn of the conservative think tank Institute for American Values, began his testimony by asserting that the best environment for children is a marriage between a man and a woman.
"The optimal environment for children is if they're raised from birth by their own natural mother, who is married to their own natural father," the author told the court, citing the "weight of evidence" by scholars on the subject.
But under persistent and at time contentious cross-examination from veteran litigator David Boies, who helped launch the legal challenge to Proposition 8, Blankenhorn seemed to concede some points to gay marriage advocates.
"I believe that adopting same-sex marriage would be likely to improve the well-being of gay and lesbian households and their children," said Blankenhorn, who remained composed and deliberate in his answers.
He also said he believed the legal recognition of same-sex marriage in the United States would make the country "more American," without explaining further.
His testimony elicited sounds of surprise from the courtroom, where a number of gay couples were in attendance.
During the past two weeks, witnesses seeking to overturn Prop 8 have testified that same-sex couples can be good parents, that their health and wealth stands to improve when married -- benefiting the public at large -- and that gay men and lesbians have historically been persecuted.
Two gay men and two lesbians have asked the federal court to rule that the right to marry has no exceptions under the U.S. Constitution. The legal battle is widely expected to reach the U.S. Supreme Court in a bid to overturn statutory prohibitions on same-sex marriage in 40 states.
A key question in the case is whether government, and U.S. voters, have a reasonable justification for denying same-sex marriage, or if the bans instead reflect discrimination and hatred.
The United States is sharply divided on same-sex marriage, which has been legally recognized in five states and the District of Columbia.
Earlier, a British child psychologist testified that the children of same-sex parents develop just as well as those brought up by heterosexual couples.
But Blankenhorn said children are the principal beneficiaries of the traditional construct of marriage -- a union between a man and a woman.
"We think of it as a gift to children. We say, 'You as a child are being given this gift of being able to know, and be known by, the two people who brought you into the world,'" he testified.
Blankenhorn also spoke at length about the "deinstitutionalization" of marriage through out-of-wedlock births, absent fathers and other societal issues. A likely outcome of legalizing same-sex marriage would be the further erosion of the institution of marriage, he said, adding that it could also open the door to calls for the acceptance of polygamy.
"Marriage is a socially approved sexual relationship between a man and a woman," he testified. "Marriage does a number of things, but the most important thing it does is regulate affiliation. It establishes who are the child's legal and social parents."
Reporting by Alexandria Sage; Editing by Steve Gorman and Stacey Joyce