Closing arguments are scheduled Wednesday in a landmark lawsuit that challenges California's ban on gay marriage.
Two same-sex couples are suing to overturn Proposition 8, which voters passed in 2008. Chief U.S. District Judge Vaughn Walker is hearing the case in San Francisco.
The case, which is the first federal trial to examine whether gay marriage bans violate civil rights, is expected to eventually reach the U.S. Supreme Court.
Backers of Proposition 8 also want the state to stop recognizing 18,000 homosexual unions that were granted before the measure took effect. In a written filing Tuesday, sponsors of Proposition 8 asked Walker to rule that government agencies, courts and business no longer have to recognize gay couples as married.
The case to overturn California's ban on gay marriage is based on the argument that it denies equal rights to same-sex couples. But it may turn on whether voters had a legitimate, reasonable reason for their decision or were motivated by discrimination.
Judge Walker set the agenda for closing arguments with a long list of questions including whether there was a good reason, or rational basis, to maintain marriage exclusively for opposite-sex couples.
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Lawyers Ted Olson and David Boies, who faced off in the 2000 Supreme Court decision that put George Bush in the White House, are challenging the California law.
They argue that same-sex couples who marry grow healthier and wealthier, their children are better of, and the state benefits from the expanded definition of marriage.
Opposite-sex marriage are not affected at all and the California constitutional amendment limiting marriage to a man and a woman -- similar to provisions in the vast majority of U.S. states -- is based in moral indignation and hate, they conclude.
Charles Cooper, the chief lawyer defending the ban known as Prop 8, argues that gay marriage would, or at least reasonably could, weaken the institution of marriage by robbing it of "special encouragement" to stay together and raise children.
"These changes are likely to reduce the willingness of biological parents, especially fathers, to make the commitments and sacrifices necessary to marry, stay married, and play an active role in raising their children," Cooper wrote.
A ruling in the case is expected within weeks.