The head of a well-known law firm and top attorney has said that he expects the US Supreme Court to resoundingly support equal marriage, when it takes on two cases challenging equal marriage bans in America.

In an interview with USA Today, David Boies said he thought that the court’s ruling, which is expected to take place in June, “will not be a 5-4 decision. I don’t know whether it’s going to be 6-3, it’s going to be 7-2,” he said. “I don’t know where it’s going to come out, but I don’t think this is going to be a 5-4 decision.”

The Supreme Court is due on 27 March to hear evidence around the case of the Defense of Marriage Act (DOMA), which defines marriage as between a man and a woman, passed under President Bill Clinton in 1996.

On 26 March, the court will also 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.

Boies, who represented Al Gore in the 2000 presidential election recount, will appear at the Supreme Court to argue in favour of equal marriage on 26 and 27 March.

He and Theodore Olson, who will appear alongside him, brought the lawsuit against California’s Proposition 8.

Speaking to USA Today, the attorney drew comparisons between the campaign for equal marriage in the US, and the struggle for interracial marriage in the 1960s. He said that opposition to both stems from the “same reservoir of ignorance” about those involved.

He went on to say that attitudes in the US had undergone a “tremendous” change, especially amongst younger generations.

“Unlike people of my generation, my children and my grandchildren have grown up living with, knowing people who were outwardly gay and lesbian. And they have learned that they’re just like us. … And when you see that they’re just like us, the rationale for discrimination melts away,” he said.

The 72-year-old did cite fears that most of the nine sitting judges “are my age or older”, and that they had lived through long-time attitudes of “extreme hostility to homosexuals.”

He added, “Judges are supposed to put that aside and our very best judges do, but it’s not an easy task.”

Boies will argue that it is detrimental to deprive gay and lesbian couples of the fundamental right to marry, not only to them, but to the children they are raising. He will also put forward that there is virtually no effect on straight peoples’ marriages, attitudes, or plans.

He said that, Chief Justice John Roberts’ decision last year to uphold President Obama’s health care reforms, showed “the court’s willingness to take a careful look at issues and not just conform to some people’s view of where they’re going to come out.”

It is likely that the Supreme Court will hear arguments that allowing equal marriage would threaten “traditional” marriage, and religious liberty.

He went on to say that he thought fears about a backlash over equal marriage were exaggerated. He said: “While people can hold moral and religious views strongly… once the Supreme Court rules on a legal right, if that legal right is not infringing on somebody else (and) not hurting somebody else, the American people accept it.”

One such argument against equal marriage came from Washington DC attorney, Ed Whelan, who filed an amicus brief against equal marriage, saying: “I think it would make the collapse of our marriage culture irreversible.”

Whelan went on to note a “marked decline” in straight marriages in the Netherlands after it legalised marriage equality in 2001, and said that it would be “very destructive to this country”.

In 2011 Mr Boies defended Judge Vaughn Walker, who made a decision to overturn Proposition 8 but faced criticism for not revealing he was in a relationship with a man at the time.