The U.S. Supreme Court on Friday halted the looming execution of an Oklahoma man after the state's attorney general conceded his murder conviction was riddled with constitutional errors and possible prosecutorial misconduct.

In a brief order, the high court agreed to put off the May 18 lethal injection execution of Richard Glossip, 60, who was convicted of plotting his boss' murder in 1997 but has continued to profess his innocence, while it considers two petitions for certiorari calling for his capital sentence to be set aside in light of newly emerged evidence casting doubt on his case. Friday's order says the stay will end if the court rejects Glossip's petitions.

"We are very grateful to the U.S. Supreme Court for doing the right thing in stopping Richard Glossip's unlawful execution," Donald R. Knight, an attorney for Glossip, said in an email statement. "There is nothing more harrowing than the thought of executing a man who the State now admits has never received a fair trial. Thankfully, for the time being, Mr. Glossip is out of peril."

Late Thursday evening, Glossip asked the court to stay his execution in light of Oklahoma Attorney General Gentner Drummond's admission that prosecutors in his case failed to turn over critical information that could have been used to impeach a key witness' testimony and result in a different verdict.

The petition, which the attorney general's office said it plans to support with a brief, asked the high court to "accept what the State's chief law enforcement officer recognizes: that Mr. Glossip's conviction is a grave miscarriage of justice, and to execute him would be an unthinkable, irreversible travesty."

A previous petition was filed in January, but at the time did not have the backing of the state's attorney general.

Drummond said in a statement posted on his office's website that he was "very grateful" that the high court issued a stay of execution in the case.

"I will continue working to ensure justice prevails in this important case," he said.

Glossip was twice convicted of orchestrating the Jan. 7, 1997, murder of Barry Van Treese, the owner of a motel in Oklahoma City where he worked as a manager. Justin Sneed, a 19-year-old handyman at the motel who was addicted to methamphetamine, confessed to beating and stabbing Van Treese to death but said Glossip told him to do it for money.

Sneed blamed Glossip, then 33 years old and without a prior record, after detectives suggested Glossip's name to him six times and told him he was facing the death penalty himself, according to court records. He was convicted of murder and is serving a life sentence in a medium-security prison without the possibility of parole.

Glossip's first conviction was thrown out in 2001 on the basis that he received constitutionally deficient legal representation at trial. In 2004, a jury convicted him again, finding that he deserved the death penalty for the murder-for-hire plot.

But two independent investigations, one led last year by a team of attorneys with Reed Smith LLP and one this year by Rex Duncan, a former state prosecutor, concluded that Glossip's conviction was clouded by constitutional violations under Brady v. Maryland, the 1963 U.S. Supreme Court decision mandating that prosecutors in a criminal case turn over all exculpatory, mitigating and impeachment evidence to defense lawyers.

The investigations found that state prosecutors never told Glossip's trial lawyers that Sneed intended to recant his testimony multiple times and that he had been diagnosed with bipolar disorders, for which he had been prescribed lithium — information that could have pushed Glossip's jury to doubt his guilt. In addition, they found that the state lost 10 boxes of evidence prosecutors had lost or destroyed.

"Do I have the choice of recanting at any time during my life?" Sneed asked his lawyer in a note, which neither Glossip's trial lawyers nor his jury ever saw. In another never disclosed note, Sneed called his testimony "a mistake." According to the Reed Smith investigation, Sneed told the firm's attorneys that over the years he had talked to his daughter and his mother about recanting his testimony, something he had previously denied. The investigation also uncovered a memo in which the trial prosecutor working on Glossip's case gave Sneed — through his attorney, who was also on the prosecution's witness list — information concerning other witness testimony in an attempt to change his own version of the facts surrounding the murder in a way that would fit the prosecutors' theory.

Glossip's case generated controversy and gathered political support nationally and in Oklahoma, a state where public support for the death penalty remains high. Sixty-two state legislators, including 45 Republicans, backed a call for an evidentiary hearing based on the newly discovered evidence in Glossip's file. In November, the Oklahoma Court of Criminal Appeals, the state's top court for criminal cases, denied Glossip post-conviction relief, preventing him from presenting any new evidence. Last month, the court again declined to consider the new evidence, arguing that it should have been brought forward sooner.

"This case is about whether legal formalities are more important than whether or not we executed somebody who's innocent," John R. Mills, another attorney for Glossip, told Law360. "The chief law enforcement officer for Oklahoma does not think that Richard Glossip has committed murder. But the state of Oklahoma is planning to murder Mr. Glossip."

On April 26, the Oklahoma Pardon and Parole Board declined to recommend clemency for Glossip, a decision that left no room for Gov. J. Kevin Stitt, a Republican, to consider a pardon. 

Two members of the board voted for clemency, and two against it. One member of the board did not vote after recusing himself in July due to a conflict of interest — his wife was one of Glossip's prosecuting attorneys. It takes three votes to grant clemency.

At the clemency hearing, Drummond said that "more likely than not" Glossip is guilty of murder but that the evidence does not prove this beyond a reasonable doubt. He urged the board to vote for his clemency in light of the recently discovered evidence.

"I believe it would be a grave injustice to allow the execution of a man whose trial was plagued by many errors," Drummond said.

It was the first time in the state's history that the chief law enforcement officer had asked for clemency for a prisoner on death row, according to a letter Drummond sent to the board last month.

Hours after the board's vote, attorneys for Glossip filed an application for a stay of execution with the Supreme Court saying Drummond supported the inmate's efforts to have his conviction vacated. 

Under the Oklahoma Constitution, the governor can only halt executions for 60-day periods without action from the board. While Stitt halted Glossip's execution twice last year, he has said he was not planning to do so again.

Mills said the two pending certiorari petitions give Glossip the last meaningful chance to avoid execution. If those fail, Glossip could seek to vacate his death sentence through habeas corpus, a legal process that allows state prisoners to challenge their incarceration in federal court on the grounds that their constitutional rights were violated, or that they are innocent.

"It was state misconduct that created the wrongful conviction," Mill said. "Executing Richard Glossip under these circumstances would be an unthinkable travesty."

Glossip is represented by Amy P. Knight, Joseph J. Perkovich and John Robert Mills of Phillips Black Inc., and Warren Gotcher of Gotcher & Beaver, and Donald R. Knight.

The State of Oklahoma is represented by Jennifer L. Crabb of the Office of the Attorney General of Oklahoma.

The first certiorari petition is Richard Eugene Glossip v. Oklahoma, case number 22-6500, in the Supreme Court of the United States.

The second certiorari petition is Richard Eugene Glossip v. Oklahoma, case number 22-7466, in the Supreme Court of the United States.

--Editing by Peter Rozovsky.