Supreme Court deliberations are supposed to be secret. So how did a draft abortion opinion leak?

WASHINGTON – What happens behind the curtains at the Supreme Court is supposed to be secret.

But that tradition – and the principle of justices being able to deliberate in private – was upended Monday after Politico published what it said is a draft opinion it obtained in one of the most significant cases before the nation's highest court in decades. That opinion showed that the court may overturn its landmark 1973 Roe v. Wade decision.

Leaks about how the justices are leaning happen – rarely. But several experts said they could not recall a draft opinion itself becoming public prematurely.

"We've had Supreme Court leaks before," tweeted Orin Kerr, a law professor at the University of California, Berkeley. "But this is a whole new order of magnitude of leak."

In 1979, Washington Post journalists Bob Woodward and Scott Armstrong published a book on the Supreme Court, "The Brethren," that set off a flurry of internal investigations after they revealed the deliberations in several major cases, including Roe itself. Years later, Woodward revealed that Associate Justice Potter Stewart was a key source.

That same year, ABC News reported the outcome of a libel case days in advance.

Five years earlier, The New York Times reported that six justices were prepared to rule against President Richard Nixon in his effort to retain recordings he made in the Oval Office that became central to the Senate's investigation in the Watergate scandal.

The outcome of Roe itself leaked to Time magazine in 1973. Then-Chief Justice Warren Burger threatened to call in the FBI to administer lie detector tests – a threat that was leaked and reported by Woodward and Armstrong.

But those kinds of leaks are so rare that they have tended to raise questions about motives and politicization of the Supreme Court, where secrecy exists to build trust among the justices so they can work their way together through complicated legal questions that are often before them.

The draft opinion on Mississippi’s strict new abortion law suggested the court is considering a decision that would overturn Roe v. Wade and reshape the landscape of one of the nation's most divisive culture war questions. "Roe was egregiously wrong from the start," Associate Justice Samuel Alito wrote in the draft obtained by Politico. "We hold that Roe and Casey must be overruled."

Hours later, in another twist, CNN reported that Chief Justice John Roberts was not in favor of overruling Roe entirely. A Supreme Court spokeswoman declined to comment.

The report reinvigorated the abortion debate months before the court had been expected to rule in the case. But it also raised fresh questions about court procedures.

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"If it is right it is the first major leak from the Supreme Court ever," tweeted Neal Katyal, a veteran litigator at the court. "It’s the pentagon papers equivalent," for the Supreme Court, he added, referencing the 1971 leak of internal Pentagon documents revealing how officials had misled the American public about Vietnam.

While advocates on both sides of the abortion debate fought over the draft opinion itself, legal experts – conservative and liberal alike – worried about the implications for the high court.

"Roberts has an absolute obligation to conduct a thorough and transparent investigation," wrote Josh Blackman, a law professor at South Texas College of Law Houston. "And at the end of that investigation, Roberts must publicly identify the persons who are responsible for this leak – that includes Justices and clerks. Heads must roll."

This article originally appeared on USA TODAY: Roe v. Wade draft opinion leak upends legendary Supreme Court secrecy