Closing arguments in the Prop 8 trial (Perry v. Schwarzenegger) began this morning in San Francisco and are expected to conclude later this afternoon. As attorneys for both sides make their remarks, Chief U.S. Judge Vaughn Walker will be basing his verdict partially on the written answers to 39 questions he posed to the parties involved in the case.

Walker’s questions challenge both the plaintiffs, who wish to overturn California’s ban on gay marriage, and the defendants, who wish to uphold the ban, but do not necessarily indicate that he favors the arguments of either side. For example, Walker asked plaintiffs to present evidence that “legal recognition of same-sex marriage reduces discrimination against gays and lesbians.” At the same time, Walker asked defendants to present evidence that “same-sex marriage has or could have negative social consequences” and to present evidence that “same-sex marriage is a drastic and far-reaching change to the institution of marriage.”

As promised at the outset of the trial, Walker’s questions indicate that he is taking an in-depth, broad-view approach to the case. Some of the questions seek to uncover whether voters passed Prop 8 with discriminatory intent, which could be viewed as a violation of the Equal Protection Clause of the 14th Amendment. Other questions aim to determine whether or not there is a constitutional right to same-sex marriage. Finally, Walker addresses the issue of federal marriage rights by asking plaintiffs, “Even if enforcement of Proposition 8 were enjoined, plaintiffs’ marriages would not be recognized under federal law. Can the court find Proposition 8 to be unconstitutional without also considering the constitutionality of the federal Defense of Marriage Act?”

Walker’s opinion, which is expected later this summer, carries significant weight. If he declares that Prop 8 violates the civil rights of gays and lesbians and overturns the ban on gay marriage, it could pave the way for sweeping change to laws in the 44 states with similar gay-marriage bans. Alternatively, a narrower ruling could affect only the states where same-sex couples are afforded all legal rights except the right to marry.

For gays and lesbians who wish to legally wed in California, Walker may also decide to issue an injunction that the plaintiffs are seeking, which would allow gay marriage to resume immediately. If the injunction is not granted, same-sex couples may have to postpone their nuptials (or at least their planned trip to the courthouse) until the case is reviewed in appellate court.

Regardless of how Walker rules, the case is expected to be appealed to the Ninth U.S. Circuit Court of Appeals and, very likely, to the U.S. Supreme Court.