Edie Windsor is used to waiting. Ms. Windsor was engaged for 40 years before her 2007 Canadian wedding to Thea Spyer. The pair waited 30 years to apply to be domestic partners, under a New York City law introduced in the 1990s. Now Ms. Windsor, 83, is waiting for the Supreme Court to decide whether to hear her challenge to the Defense of Marriage Act, with a decision expected Monday morning.

[In Windsor v. United States] Ms. Windsor is requesting a refund of the $363,053 in estate taxes that she paid to the IRS after being left all of Ms. Spyer’s property when she died in 2009. Had the pair been classified as married, Ms. Windsor would have been able to inherit the property shielded from taxes. Instead she was classified as if they had no relation to each other.

Ms. Windsor’s case has the potential to help strike down the definition of marriage in the 1996 Defense of Marriage Act, where it is defined as between a man and a woman. If she wins, the federal government will recognize the marriages of same sex couples in states where gay marriage is already legal, resolving a currently conflicting definition between the federal and state governments. The district court decision in Hollingsworth v. Perry, the case challenging California’s Proposition 8 that prohibited gay marriage, declared a broader right to gay marriage, but SCOTUS is viewed as more likely to take Windsor.

“I’ve been asked, how would I feel if we win?” said Windsor. “What would that mean? It would mean everything. The beginning of the end of the stigma.”

...Roberta Kaplan, a partner at Paul Weiss, has been working on the case pro bono along with the American Civil Liberties Union. Ms. Kaplan has pressed to expedite the process due to her client’s age, saying that “she wants to be alive when she wins.”

...Ms. Kaplan thinks that the money involved makes the case a good one for the Court. “I think every American gets in their gut what it means to pay a huge tax bill that you wouldn’t have had to pay if it weren’t for this discrimination,” she said, adding that the facts of Ms. Windsor’s life, being part of a decades-long loving relationship through intolerance and Ms. Spyer’s 30-year battle with multiple sclerosis, create a compelling story.

“I have a lousy heart,” said Ms. Windsor, who has suffered from a series of heart attacks, most recently this spring while walking close to her Greenwich Village home. She also survived emergency open-heart surgery in 1996.