Oklahoma Attorney General Gentner Drummond on Monday filed a motion to stop death row inmate Richard Glossip's ninth execution date.

The move comes after the Oklahoma Pardon and Parole Board on April 26 denied clemency for Glossip, 60, who has been twice convicted in a murder-for-hire plot to kill his boss in 1997 but maintains his innocence.

"The profound problems with Mr. Glossip's conviction have again garnered unprecedented support, this time coming from the Oklahoma Attorney General's Office, now represented by none other than Paul Clement," Glossip's attorney, John Mills, said in a Monday statement. "We hope that the Court will take notice and prevent the grave injustice that would come from executing an innocent man."

Clement served as the U.S. solicitor general appointed by George W. Bush between 2005 and 2008.

Glossip's latest death date is scheduled for May 18.

OKLAHOMA DEATH ROW INMATE RICHARD GLOSSIP DENIED CLEMENCY AS HE FACES 9TH EXECUTION DATE

Oklahoma man mugshot

The Oklahoma Pardon and Parole Board on April 26 denied clemency for Glossip, 60, who has been twice convicted in a murder-for-hire plot to kill his boss in 1997 but maintains his innocence. (Oklahoma Department of Corrections via AP, File)

The 60-year-old man has spent 25 years in prison for his conviction in the 1997 murder of motel owner Barry Van Treese. Oklahoma prosecutors allege Glossip killed Van Treese, the owner of a motel where Glossip worked as a manager, by convincing a 19-year-old maintenance worker, Justin Sneed, to execute his killing.

While Drummond does not believe Glossip is innocent in Van Treese's murder, the attorney general said he does deserve a new and fair trial due to various mistakes by the state in his case.

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"Simply put, the State does not agree with everything Glossip has said in this case or in this Court.… But having come to the difficult but essential conclusion that Glossip’s capital conviction is unsustainable and a new trial imperative, the State agrees that a stay pending resolution of Glossip’s forthcoming petition is appropriate," Drummond wrote in his recent motion supporting a stay of execution. 

Oklahoma Attorney General Gentner Drummond

Drummond has said that while he does not believe Glossip is innocent in Van Treese's murder, he does deserve a new and fair trial due to various mistakes by the state in his case. (Sue Ogrocki)

Glossip's attorneys argue that Sneed was Van Treese's sole killer.

Sneed was sentenced to life after pleading guilty to beating Van Treese to death with a baseball bat in 1997 in a room at the Oklahoma City motel. Sneed testified that he killed Van Treese but only after Glossip, the motel manager, promised to pay him $10,000 to commit the crime. However, Glossip's attorneys argued that his murder-for-hire conviction and death sentence were unsubstantiated. 

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"New evidence has shown that Justin Sneed, the person who committed the murder and the star witness for the prosecution, lied on the stand and wanted to recant his false testimony," Glossip's attorney, Don Knight, said in an April 26 statement. "If the jury had known what we know now, they never would have convicted Mr. Glossip."

Oklahoma County District Attorney David Prater to respond to the petition to review Richard Glossip's case.

Glossip has spent 25 years in prison for his conviction in the 1997 murder of motel owner Barry Van Treese. (Fox News Digital)

Last week's clemency hearing came after independent investigations by the Reed Smith law firm and Drummond's office that alleged prosecutorial misconduct in Glossip's murder trial

"After thorough and serious deliberation, I have concluded that I cannot stand behind the murder conviction and death sentence of Richard Glossip," Drummond said after the conclusion of the investigation.

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During the clemency hearing, Glossip told the court via Zoom: "I’m not a murderer, and I don’t deserve to die for this."

The victim’s family, however, remained firm in their belief that Glossip killed Van Treese.

Richard Glossip behind bars

During the clemency hearing, Glossip told the court via Zoom: "I’m not a murderer, and I don’t deserve to die for this." (Fox News Digital)

Van Treese's niece said her "family knows that if it were not for Richard Glossip… Barry would be here."

"We know in our hearts that he is responsible for the death of Barry," she said, calling Glossip a "habitual liar."

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Meanwhile, Glossip's wife described the 60-year-old man as patient and lighthearted despite his circumstances.

"Having lost 26 years of his life… today, he is on the brink of his ninth execution date, all for a crime he did not commit," Glossip's wife said, describing his continuously delayed execution date and fight for clemency as "psychologically terrorizing."