A second federal gay marriage trial is possible in a Massachusetts lawsuit that challenges the constitutionality of the Defense Of Marriage Act (DOMA), the 1996 law that defines marriage as a heterosexual union for federal agencies and allows states to ignore legal gay marriages performed outside their borders.

Gay & Lesbian Advocates & Defenders (GLAD), the Boston-based gay rights advocacy group at the center of the gay marriage debate in New England, filed the lawsuit in March on behalf of seven gay married couples and three surviving spouses from Massachusetts.

Motions filed by both parties – the government wants the lawsuit dismissed, while GLAD is requesting a ruling in its favor – will be heard Thursday by a federal judge in Boston.

If the judge orders a trial, it would be the second trial at a federal level concerning gay and lesbian couples' right to marry.

The first such trial is expected to wrap up in June after a federal judge heard more than three week's worth of testimony in January. Lawyers representing a gay and a lesbian couple argued that California's gay marriage ban, Proposition 8, violates their constitutional rights.

GLAD's case focuses narrowly on federal benefits being denied to legally married couples in Massachusetts, the first state to legalize the institution in 2004.

One plaintiff, Dean Hara, the widower of former U.S. Rep. Gerry Studds, the first openly gay member of Congress, has been denied the Congressman's pension and other benefits extended to surviving spouses.

“It hurts,” said Hara, who married Studds in May 2004. “But at the same time I realize that I, as a man, need to stand up for what I believe in. This is a nation of laws, and we're all supposed to have equal treatment under the law.”

While the Obama Administration says it supports repeal of the law, the Department of Defense argues it has a responsibility to defend the laws enacted by Congress.

Both lawsuits are likely to reach the Supreme Court.