Both sides in the legal battle over California's gay marriage ban filed final briefs Friday, signaling closing arguments are closer at hand in the high-profile trial considering the constitutionality of the measure, the San Francisco Chronicle reported.

In their filing, proponents of Proposition 8, the gay marriage ban narrowly approved by California voters in 2008, maintain that voters approved the measure because they believe allowing gay men and lesbians to marry would hurt children, an argument advanced by the campaign to approve Proposition 8. The measure trumped a state Supreme Court ruling that legalized gay marriage in California for a brief time.

“Californians voted for Proposition 8 because they thought it would strengthen the institution of marriage [and] … because they thought it would benefit children,” lawyers for, the chief sponsor of the measure, said.

Chief U.S. District Judge Vaughn R. Walker cleared his San Francisco courtroom after hearing two and a half weeks worth of testimony in January without a ruling, saying he wanted to review the evidence before listening to closing arguments.

Lawyers in favor of gay marriage – led by the constitutional team of Ted Olson and David Boies – argued that proponents of Proposition 8 approved the measure out of animus towards gay men and lesbians, stripping such couples of their constitutional rights.

The trial began with the emotional testimony of a gay and a lesbian couple who have been denied the right to marry in California because of Proposition 8. Jeffrey Zarrillo said he loved Paul Katami “probably more than I love myself.” And Sandra Stiers testified that she was a plaintiff in the case because she wanted to marry her partner of ten years, Chris Perry.

As the trial progressed, plaintiffs' lawyers trounced the defense as they strung together weeks' worth of testimony from 17 witnesses, including plaintiffs. In contrast, Proposition 8 lawyers controlled the courtroom for only two days, offering testimony from only two expert witnesses.

And in the cross-examining, one of those witnesses cracked under the pressure of Boies' persistent questioning.

Boies devastated David Blankenhorn, founder and president of the conservative think tank Institute for American Values, who admitted that legalizing gay marriage would “improve the well-being of gay and lesbian households and their children,” that homophobia is a “real presence” in our society and that gay marriage in the United States would make the country “more American.”

Witnesses for the plaintiffs included the testimony of Letitia A. Peplau, a social psychologist at the University of California, Los Angeles, who testified that her research showed that “on average the level of quality is the same” as measured by closeness, love and stability between gay and straight couples.

Michael Lamb, head of Cambridge University's Department of Social and Developmental Psychology, said he concluded that “The evidence makes clear that having a gay or lesbian parent does not make children more likely to be maladjusted” after reviewing the data of about 100 studies on the subject. And that gender is not an important measure of good parenting.

“What makes for an effective parent is the same whether or not you are talking about a mother or a father,” Lamb said.

Attorneys for the Proposition 8 campaign attempted to portray plaintiffs' witnesses as “committed liberals” who are prepared to advance the gay rights movement.

In their filing Friday, plaintiffs' lawyers cited their witnesses' testimony in concluding that allowing committed gay couples to marry “strengthens the institution of marriage for both same-sex couples and opposite-sex couples.”

No matter how Judge Walker rules, the decision is widely expected to be appealed all the way to the Supreme Court, whose ruling could affect gay marriage bans throughout the country.