The big difference?
Utah got to go first.
That means going into Thursday's arguments, the judge's initial leanings are already known, and how the panel probes each side in Oklahoma's case may reveal to Utah and the world how the high court may ultimately rule in coming weeks.
"The same core constitutional question is presented by both cases," said Carl Tobias, judicial appointment expert and professor at the University of Richmond School of Law. "Maybe they're going to ask questions they really want answered, or the judges on either side will use the time to try to persuade the person in the middle."
After Utah's same-sex marriage hearing last week, it seemed Kelly was squarely on the state's side, while Lucero voiced strong concerns about the law's social and legal impact on gay couples and their children.
Holmes seemed conflicted, lobbing challenging questions to both Utah's lead counsel Gene C. Schaerr as well as Peggy A. Tomsic, who represents the three couples challenging Utah's law.
"The judges have had time to rethink their views since the [Utah] argument, but that doesn't mean those views have changed any," Tobias said. "The vote to be gotten is still Holmes."
Tomsic, who argued before the court just last week, will be seated Thursday in the gallery, watching.
Utah Attorney General Sean Reyes will not attend the hearing in Denver, spokeswoman Missy Larsen said, but he will be watching from afar with "great interest."
"Everyone in our office is definitely watching to see how it will play out in court," Larsen told The Tribune. "Because the issues presented are so very similar to the ones facing our state, this is a critical discussion that will continue with the arguments and questions in the Oklahoma case."
Less than a month after U.S. District Judge Robert J. Shelby made history in striking down Utah's constitutional ban on same-sex marriages, U.S. District Judge Terrence C. Kern became the third federal judge to overturn a state law prohibiting gay and lesbian unions on Jan. 14 in Oklahoma.
The ban was "an arbitrary, irrational exclusion of just one class of Oklahoma citizens from a governmental benefit," Kern wrote in his decision. "The Court recognizes that moral disapproval often stems from deeply held religious convictions. [...] However, moral disapproval of homosexuals as a class, or same-sex marriage as a practice, is not a permissible justification for a law."
The embattled Oklahoma amendment was adopted in 2004 with 75 percent of voters backing the claim that "marriage in this state shall consist only of the union of one man and one woman."
Utah's famed Amendment 3 was passed that same year with 66 percent of the vote.
Like Utah, Oklahoma's impetus for passing such a law was rooted in its attempt to maintain a "traditional" definition of marriage and promote an institution state officials argue benefits children.
Kern cited Shelby's decision in his 68-page opinion, ruling that, as in Utah, the justification for such a law had no rational basis.
Although there is no official time frame for when the 10th Circuit may issue its determination, experts said the two cases are expected to be resolved together either in a joint ruling or in separate rulings issued at the same time.
Last week, Tomsic asked the judges to ensure marriage rights for all, while Schaerr asked the panel to preserve "man-woman marriage."
Schaerr argued that at the core of these cases is the question of whether states can define marriage for themselves. Utah's position is that they can.
He also argued that having a both mother and father is essential to the success of children. But on the eve of Utah's hearing, Schaerr filed a letter with the court distancing the state from research by Mark Regnerus of the University of Texas, which Utah used in its briefs to bolster the claim that opposite-sex parenting is the "gold standard" for children.
Oklahoma makes similar claims in its briefs to the court, which, experts said, may be fodder for the judges come Thursday.
Tomsic argued that every major psychological and sociological organization has come to the exact opposite conclusion regarding children.
She also noted that same-sex couples raise and have been raising children together for years. She argued restrictions on civil marriages disenfranchise these families and ultimately harm these children.
Among the chief differences between the two states is the fact that some 1,300 same-sex couples in Utah were allowed to marry in the 17 days after Shelby's ruling and before the U.S. Supreme Court granted the state a stay that halted the weddings.
If the 10th Circuit Court of Appeals rules in favor of the plaintiffs in both cases, that would effectively outlaw bans on same-sex marriages in Utah, Oklahoma, Colorado, New Mexico, Wyoming and Kansas.
But whichever way the circuit court rules, it is likely the judges will stay their decision until the U.S. Supreme Court rules on the question.
Oklahoma's arguments before the 10th Circuit Court of Appeals begin Thursday at 1:30 p.m.
A look at the cases
On Thursday, the 10th Circuit Court of Appeals will hear its second case in as many weeks challenging a state ban on same-sex marriage. Experts have said the Utah and Oklahoma are remarkably similar. Here are some key differences:
• Oklahoma's case, filed by Sharon Baldwin and her partner of 17 years, Mary Bishop, has been pending for nearly a decade. Utah's case was filed last year.
• More than 1,300 gay and lesbian couples were legally married in Utah after the ban was overturned. The federal judge in Oklahoma immediately issued a stay, preventing a similar circumstance.
• The issue of marriage recognition for couples who wed in other states where gay marriage is legal remains up in the air in the Oklahoma case. The district court found it could not rule on that part of the lawsuit because the Tulsa County clerk, who was sued, does not have the authority to recognize such unions. Utah's lawsuit named the governor, attorney general and Salt Lake County clerk in its suit, eliminating this question of proper authority. The Oklahoma couple suing for marriage recognition are appealing their case.