Evidence will be heard today in a lesbian couple from Detroit’s lawsuit to try to adopt each other’s children by overturning Michigan state’s ban on same-sex adoption. The legal action escalated into a potentially groundbreaking case against the ban on equal marriage in the state.

Two Detroit nurses filed a lawsuit in August attempting to overturn restrictions on adoption for same-sex couples, however by the judge’s decision, the case will now go on to test the legality of a 2004 constitutional amendment which specifies that Michigan only recognises marriage between heterosexual couples.

Arguments will be heard today in the case at Detroit law school by District Judge Bernard Friedman. He has not specificed when he will make a ruling, but if he did rule that the amendment was unconstitutional, equal marriage supporters have claimed that same-sex couples will immediately be able to adopt, and get married.

Some state officials, however, have claimed that “potential legal chaos” will take place if the ban is lifted.

“This is not the road we thought we’d go down,” Jayne Rowse, 48, said in an interview with the Associated Press. “We thought Judge Friedman would rule one way or the other on second-parent adoption. No one anticipated this. It was out of left field.”

Her partner, April DeBoer, 41, said the lawsuit was filed because they wanted to protect their three children.

“I know we’re taking on a bigger issue with same-sex marriage,” she said.

Rowse and DeBoer have lived together for over six years with three children, Nolan, 4, Jacob, 3, and Ryanne, 3, a girl, who were unable to be raised by their birth parents.

The two boys were adopted by Rowse, and DeBoer adopted Ryanne, seperately, however under state law, it is impossible for the couple to adopt each other’s children because they aren’t married.

The Associated Press reports that, if one woman died, even if it were to be explictely spelled out in a will, the other parent would not be automatically recognised as the legal parent of the children.

“It could be contested, just like anything in a will. If one of my family members said, `I want the kids,’ a judge could say, `This is family. She’s not,'” Rowse said, referring to DeBoer.

“One of our big concerns is they consider themselves siblings,” Rowse said of the children. “They could be separated. That’s not fair to them. They’re brothers and sister.”

At a court hearing in August, the judge changed the case, when he suggested that the couple should challenge the state’s ban on equal marriage.

The state approved the ban in 2004, with 58% of voters in favour of it.

The couple then changed their suit to suggest that the bar on equal marriage violated the US Constitution’s equal protection clause as it treats gay couples differently to straight ones.

Michigan attorney general’s office responded to the announcement that Friedman would hear arguments on the case, saying that there was no “fundamental right to same-sex marriage”.

“Michigan’s marriage amendment bears a reasonable relation to legitimate state interests,” the state said. “Michigan supports natural procreation and recognizes that children benefit from being raised by parents of each sex who can then serve as role models of the sexes both individually and together in matrimony. Plaintiffs fail to allege facts showing there is no rational basis for these legitimate state interests.”

Even if the judge rules against lifting the ban on equal marriage, the Supreme Court’s eventual ruling on whether federa

The Supreme Court is due on 26 March to take up the case of whether to overturn Proposition 8, which in 2008 added a clause to the Californian constitution stating that marriage could only be recognised by the state if it were between a man and a woman, causing widespread controversy.

One brief was filed by the American Civil Liberties Union urges the judge to allow the adoption. No requests in opposition to lifting the equal marriage ban were filed.

A former state lawmaker who supported the 2004 constitutional amendment, Jack Hoogendyk, said he remains in favour of the ban, but said it “might barely pass today” if it was on the ballot, or that it may even be defeated.

“A good moral culture starts with the family, and an ideal family unit is two parents – a father and a mother,” he said. “It’s good public policy to uphold that ideal.”