In a second day of landmark hearings, the US Supreme Court is to take on arguments around the Defense of Marriage Act (DOMA), which bans equal marriage across the US.

In yesterday’s hearing, the court heard oral arguments around Proposition 8, the state of California’s 2008 ban on equal marriage, the justices questioned the meaning of marriage, and challenged arguments for the ban.

DOMA nationally defines marriage as “a legal union between one man and one woman”.

In October, the 2nd Circuit Court of Appeals in New York said the law violated the equal protection clause of the US Constitution.

The case was brought to the court by Edith Windsor, a lesbian widow forced to pay more than $350,000 (£231,000) in federal estate tax after her wife died.

The American Civil Liberties Union filed a petition on behalf of 83-year-old Edith Windsor, who was treated in law as if she and her late wife Thea Spyer were strangers.

The Defense of Marriage Act was signed into law in 1996 by former President, Bill Clinton. Mr Clinton recently said “I have come to believe that DOMA is contrary to [constitutional] principles”, and his wife, former US Secretary of State Hilary Clinton, came out in support of marriage equality in a video last week.

David Boies, one of the country’s top attorneys predicted the Justices would rule overwhelmingly in favour of marriage equality, saying “It’s going to be 7-2″.

Since the hearing on Proposition 8 began yesterday, some have predicted that the court may shy away from ruling on the controversial laws.

Recently, evidence has emerged that the tide of opinion among the public and lawmakers is turning in favour of marriage equality.

Democratic Senator Claire McCaskill and Republican Senator Rob Portman are the most recent politicians to officially announce their support for same-sex marriage.

A widely cited poll published one week ago revealed 58% of Americans now support the legalisation of same-sex marriage, while 36% oppose it.

Despite the trend toward support for same-sex marriage, Daily Beast analyst Michael Tomasky predicted that SCOTUS may still uphold Proposition 8 as the conservative Justices may take a hard line to make a political point.

“They might see themselves, what with people like Senator Portman buckling to the sodomite lobby, as the last line of defense, the last moral men in a crumbling universe,” he said.

Thousands of social media users have taken to Facebook and Twitter, to change their profile pictures to an altered version of the Human Rights Campaign (HRC) logo, in support of equal marriage.

High profile posters of the altered logo included Beyoncé and Madonna, as well as Star Trek’s George Takei, and the satirical Facebook page for God, which posted an image of Ladies Liberty and Justice kissing.

A decision on the cases is likely to be made by the end of June.