DENVER -- A close decision is expected from the three federal appeals judges who took up the case of Utah's ban on same-sex marriage.

In arguments Thursday, the judges from the 10th U.S. Circuit Court of Appeals grilled lawyers for the state of Utah and the plaintiffs suing over Amendment 3 about interracial marriage bans, discrimination, state's rights, the will of the people and constitutional rights.

The three couples who sued Utah over Amendment 3 -- Derek Kitchen and Moudi Sbeity; Laurie Wood and Kody Partridge; and Karen Archer and Kate Call -- sat in a row behind their lawyers as arguments were being made. At times, Sbeity would but his arm around his partner; Wood and Partridge clutched each other's arms.

Click here for audio of the arguments before the 10th U.S. Circuit Court

Almost immediately, Judge Jerome Holmes pressed the state about interracial marriage bans in the 1960s, grilling special assistant Utah Attorney General Gene Schaerr about Loving v. Virginia.

"What barred them from getting married was race. And in this instance, why is that any different? You have a man who wants to marry another man. The only thing that bars him from getting married, is gender," Holmes asked. "So why is that any different from Loving where you're drawing a line that is based upon a protected classification? Why shouldn't this be a situation of evaluating the gender for intermediate scrutiny?"

"The Supreme Court's decision in Loving did not intrude into the state of Virginia's definitional authority over marriage," Schaerr replied. "The exclusion of mixed race couples was a regulatory exclusion."

Schaerr argued that the traditional definition of marriage must be preserved, not only because it was the will of the people who approved Amendment 3 -- but to preserve a view that "fathers and mothers" are important.

Judge Carlos Lucero seemed skeptical.

"Why is a heterosexual couple more likely to get married if gay couples aren't allowed to get married?" he asked.

In his own line of questioning, Judge Paul Kelly, Jr., quizzed Peggy Tomsic, the attorney for the plaintiffs, about the voters who approved the ban on same-sex marriage by a large majority.

"We can't just ignore what the legislature has done and say, 'We don't like that so your animus is bad,'" he told Tomsic.

"Has public policy ever been allowed to overrule constitutional rights in this country?" Lucero chimed in.

"No, your honor," she replied.

The state of Utah recently backed off of using a highly controversial study that claimed children of same-sex parents did not fare as well as the children of same-sex parents. The Regnerus study has been discredited and the state told the court it would not cite it as much in arguments that Amendment 3 is needed for a "child centric" environment.

"The bottom line is that the science is inconclusive," Schaerr said of the study.

"Well, if the science is inconclusive and if we're at anything above rational basis, you lose on that point, right?" Holmes countered.

Based upon the questioning, it appeared that Judge Lucero was siding with the plaintiffs, while Judge Kelly was siding with the state. Judge Holmes was viewed as a "swing vote."

Amendment 3, which defines marriage as between a man and a woman and doesn't recognize anything else, passed in 2004 with 66 percent of the vote. After U.S. District Judge Robert Shelby overturned it, more than 1,200 same-sex couples married in Utah until the U.S. Supreme Court halted it pending the appeal.

The 10th U.S. Circuit Court of Appeals is expected to decide the case within two to six months. Next week, Oklahoma's same-sex marriage ban will be considered by the same panel of judges.

Outside court, the plaintiffs in the case expressed optimism they would prevail.

"We are hopeful that we will see a wonderful decision come out of this court," said Kody Partridge, hugging her wife, Laurie Wood.

Utah Attorney General Sean Reyes told FOX 13 he was also confident in his side's case, but added that it would be a "close decision."

"I think this case fundamentally is about the right for a state like Utah to be able to determine something as significant and fundamental as marriage through the democratic process," he said.

Just before the hearing, Reyes walked up to the plaintiffs and spoke with them. He later told FOX 13 that he said he was "sorry" for any pain they've gone through in the case and that -- to the extent it was possible -- it was not personal.

"I've tried to put myself in their shoes. I understand they feel pain and to that extent I wanted to express to them that I'm sorry that they're feeling that," Reyes said. "I'm not sorry to be representing the state of Utah. I want to be clear that's my duty."

Derek Kitchen and Moudi Sbeity said it is personal.

"Our lives are on the line and our lives are as personal as it gets," Sbeity said.

"It's not just us, there are thousands of other same-sex couples that are directly affected," Kitchen added. "I don't think he quite understands the harm that he is doing."

A cache of court documents relating to the Amendment 3 appeal are available here.

Click here for FOX 13 News' ongoing coverage of the case.