A prominent lawyer who argued against the Defense of Marriage Act (DOMA) at the Supreme Court has predicted nationwide marriage equality as early as next year.

Paul Smith was part of the legal team that last year successfully challenged a key provision of DOMA in a case that reached the Supreme Court. DOMA's demise led to the federal government's recognition of gay couples' marriages. The court's landmark decision has served as the basis for many of the dozens of state challenges that followed.

Challenges to bans in Virginia, Oklahoma and Utah are farthest along in the appeals process. Smith said one of those cases could reach the Supreme Court by next summer.

“I think that most observers think there are five votes [on the Supreme Court] for the pro-equality side – the same five that felt the Defense of Marriage Act was unconstitutional,” Smith told Vox.

The high court could also decline to hear any of the cases. Unanimous rulings against the restrictive marriage bans would also lead to nationwide marriage equality. However, Smith said his “personal view is that the Supreme Court wants to be the one to decide this issue, not the lower courts.”

“So the Supreme Court will probably take it,” Smith added.