Los Angeles ? Scholars, gay and lesbian partners and opponents of same-sex marriage are expected to testify about the nature of marriage and homosexuality itself during an unprecedented federal trial today to determine whether gays and lesbians may marry.

The case, Perry v. Schwarzenegger, is expected to become a landmark that eventually will be decided by the U.S. Supreme Court. Both sides have hired leading legal advocates with lots of experience before the high court.

San Francisco’s U.S. District Court Judge Vaughn R. Walker, a Republican appointee known for independence, will decide whether Proposition 8’s ban on same-sex marriage violates U.S. constitutional rights of equal protection and due process. Walker’s pretrial rulings have tended to favor supporters of same-sex marriage. Unlike other court cases about marriage rights, the trial before Walker will involve weeks of testimony from witnesses on wide-ranging issues.