Whether the justices will accept the case -- which would come to them out of the 9th U.S. Circuit Court of Appeals, generally believed to be the most liberal appeals court in the country -- and how they would rule if they accepted the case is highly speculative at this point.
The battle against gay and lesbian marriage in California was engaged in 2000 when alarmed voters enacted the California Defense of Marriage Act, Proposition 22, a law that banned same-sex marriage or the recognition of such a marriage performed in another state. The margin was wide: 61 percent voted for the new law, which said simply, "Only marriage between a man and a woman is valid or recognized in California."
Since it was a state law, it was vulnerable to court challenge. In about a month, it was struck down by the California Supreme Court 4-3, which said it violated the rights of gays and lesbians. The majority included the Republican-appointed chief justice. Democratic state officials then allowed the law to die.
However, in November 2008 state voters, by a margin of about 52 percent to 48 percent, voted to make the language of the outlawed statute an amendment to the state Constitution, protecting it from challenge in state courts.
Two gay couples in San Francisco then challenged the amendment as unconstitutional in federal court.
An insightful article in the Sacramento Bee said the challengers hoped the San Francisco venue would give them an advantage, but by the luck of the draw they ended up with U.S. Chief District Judge Vaughn Walker, a conservative appointed by President George H.W. Bush. He is hearing the case without a jury.
The Bee said the ongoing federal trial is less about presenting evidence than "a sociological and philosophical debate," with some saying same-sex couples have the right to marry and others saying there is no such right.
If and when the case reaches the U.S. Supreme Court, Justice Anthony Kennedy -- a moderate conservative, a Catholic and a native of Sacramento -- may be the key to its resolution. Kennedy is balanced between the high court's four-member conservative bloc and its four-member liberal bloc. In many cases, his vote is the deciding one and he writes the majority opinion.
The Bee article acknowledges Kennedy's swing vote potential, but says he "is not by nature a legal trailblazer."
But there is plenty of evidence otherwise.
In 2003's Lawrence vs. Texas, Kennedy wrote the 6-3 majority opinion striking down Texas' anti-sodomy law, which made it "a crime for two persons of the same sex to engage in certain intimate sexual conduct." Kennedy said it violated the due process, or fair proceedings, guarantee of the U.S. Constitution.
Kennedy's landmark opinion also made it clear that it was time for government to get out of the bedroom.
"Liberty protects the person from unwarranted government intrusions into a dwelling or other private places. In our tradition the state is not omnipresent in the home," he wrote.
Referring to homosexuals, he said: "The state cannot demean their existence or control their destiny by making their private sexual conduct a crime. Their right to liberty under the Due Process Clause gives them the full right to engage in their conduct without intervention of the government."
He added the framers of the Constitution were fully aware that laws deemed necessary in one generation can later "serve only to oppress. As the Constitution endures, persons in every generation can invoke its principles in their own search for greater freedom."
Kennedy is also no stranger to striking down voter-enacted amendments to state constitutions.
In 1996's Romer vs. Evans, the high court weighed Colorado's Amendment 2, a voter-enacted change to the state Constitution that banned all state and local action designed to protect the status of people based on their "homosexual, lesbian or bisexual orientation, conduct, practices or relationships."
Kennedy wrote the majority 6-3 opinion striking down the amendment as unconstitutional, saying in part, "This disqualification of a class of persons from the right to obtain specific protection from the law is unprecedented and is itself a denial of equal protection in the most literal sense."
Meanwhile, an Angus Reid Public Opinion poll indicates most Americans predict the U.S. Supreme Court will uphold Proposition 8. The online survey of a representative sample of 1,000 U.S. adults found 52 percent expect the justices to rule marriage is between a man and a woman only while 28 percent say the justices will define "marriage as a union of two people, regardless of gender." The poll, with an error rate of 3.1 percentage points, was conducted in January 2009, but only recently announced.
The challenge in California is certainly drawing national attention. There also are indications the trial is causing some bitterness.
Catholic League President Bill Donohue said the trial judge allowed attorneys in the case "to submit e-mails they obtained between the director of the U.S. Conference of Catholic Bishops and the bishops. Allowing such communication in a trial is unusual enough, but the purpose was even more invidious: To show that Catholics played a major role in passing Proposition 8. The lawyers did the same thing to Mormons, offering more e-mail 'proof' of their involvement."
The lawyers' goal, Donohue said, "is not to contest the First Amendment rights of Catholics and others -- their goal is to put religion on trial."
Proponents of Proposition 8 successfully asked the U.S. Supreme Court to block live streaming of the trial on YouTube. But a group of Hollywood movie producers and actors sympathetic to the challengers has been acting out the process for YouTube broadcast.
Hollywood aside, testimony in the San Francisco trial has ended. Judge Walker is expected to schedule closing arguments next month. The next stop should be the 9th Circuit. Then, in all probability, the U.S. Supreme Court.