The Oklahoma Pardon and Parole Board on Wednesday declined to recommend clemency for Richard Glossip, a death row inmate whose murder conviction has been criticized by legal experts — and the state's top prosecutor — as tainted by errors and constitutional violations.

Two board members voted to recommend to the governor, who is bound by the decision, that Glossip be spared from death — one vote too few. The decision paves the way for his execution on May 18.

Hours after the board's decision, Glossip's attorneys filed an application for a stay of execution with the U.S. Supreme Court, saying the state's attorney general, Gentner Drummond, supported the inmate's efforts to have his conviction vacated.

"Although the state does not oppose Mr. Glossip's request for a stay of execution, the Oklahoma Department of Corrections has begun preparing to execute Mr. Glossip," the application said. "His case has generated conflict and controversy, including at this Court. But he comes to this Court as an individual who, whatever his shortcomings and mistakes, has done nothing to justify his execution."

At the clemency hearing, Drummond asked the board to vote for clemency in light of recently discovered evidence that cast serious doubts on Glossip's guilt. 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.

Glossip was convicted of arranging the 1997 murder of Barry Van Treese, the owner of a hotel-motel in Oklahoma City where he worked at the time. He has been on death row for 25 years and narrowly escaped the death chamber three times.

A state jury had found that an aggravating factor — hiring someone to do the killing — warranted the death penalty for Glossip, who has continued to maintain his innocence.

Justin Sneed, a maintenance man at the hotel who was struggling with a meth addiction, confessed to bludgeoning Van Treese with a baseball bat and stabbing him to death, but under a plea deal with prosecutors, testified that it was Glossip who asked Sneed to kill the man.

Sneed was spared the death penalty in exchange for being the key witness in Glossip's prosecution and is serving a life sentence without the possibility of parole.

A state appellate court previously found that Glossip had received ineffective counsel assistance at trial and an independent investigation conducted last year by law firm Reed Smith LLP at the request of Oklahoma state legislators recently found several deficiencies and errors with how Glossip's legal case has proceeded through the court system.

At the parole hearing, Jackson Walker LLP's partner Christina Vitale, who co-led the independent investigation, told the board to consider the newfound evidence that was never presented to the juries hearing Glossip's case, including statements by Sneed, who discussed recanting his testimony and wanting to break his plea agreement before and after Glossip's trial.

The investigation also found impeaching evidence on Sneed, including a 1997 diagnosis of bipolar disorder that could have cast doubt on his credibility and memory recall, evidence that prosecutors failed to turn over to Glossip's trial attorney.

In addition, Reed Smith attorneys found evidence that one day before Sneed testified, prosecutors had shared with him — through his lawyer, who was also on the prosecution witness list — other witness testimony, including that of a medical examiner, after which Sneed changed his own version of the events surrounding the murder.

The jury who convicted Glossip's at the end of his retrial in 2004 — the Oklahoma Court of Criminal Appeals unanimously threw out his first conviction in 2001 after finding that he had received unconstitutionally ineffective assistance of counsel — didn't know the state had destroyed evidence that could have cast doubts on his guilt, Vitale told the board.

A separate independent investigation of Glossip's criminal case ordered by the state attorney general and led by Rex Duncan, a former prosecutor, found that the "cumulative effect of errors, omissions, lost evidence and possible misconduct cannot be underestimated," and concluded that his conviction should be vacated.

Last week, the state Court of Criminal Appeals decided that it would not review Glossip's case a second time despite the new evidence, saying its authority to review the conviction was restricted by state law.

Drummond and two other state elected officials, Rep. Kevin McDugle and Rep. Justin Humphrey, all Republicans, warned the parole board that allowing Glossip's execution to go forward would tarnish the integrity of the state's justice system and undermine its credibility.

"We should be tough on crime. But we have to be just. Our death row system must be pure. We have to know when we're putting people to death, they're deserving it," McDugle said. "I believe he is innocent of the charge of murder. I believe there are too many mistakes in this case."

But the board, which is one member short due to the recusal in July of Richard Smothermon — whose wife is a prosecutor who was involved in Glossip's case —ultimately decided to deny clemency with a quick voting session that included no comments.

Edward Konieczny, a former police officer and retired bishop of the Episcopal Diocese of Oklahoma, and Calvin Prince III, a former court administrator who served on the board of the state's Department of Corrections, are the two members who voted to recommend clemency.

The two board members who voted against it are Cathy Stocker, a former district attorney who also served as chair of the Oklahoma Ethics Commission, and Richard Miller, a retired trial judge who also served on the emergency division of the state's Court of Criminal Appeals, the state's highest court for criminal matters.

On Monday, Glossip's attorney filed a suit asking a state court to prevent the board from holding a clemency hearing without a full five-member board.

Under the state constitution, the Pardon and Parole Board must recommend a pardon, commutation or parole before the governor can grant one. The governor can halt executions only for 60-day periods without action from the board but does not have the power to unilaterally issue pardons.

Since Glossip has been sentenced to the death penalty, his execution has been postponed six times, including twice by the state's current governor, J. Kevin Stitt, also a Republican, who issued stays in August and in November of last year. 

Don Knight, an attorney for Glossip, said in an email statement after the hearing that he would pursue all avenues available in the court system to stop what he called an "unlawful judicial execution," and called on the governor to issue a stay to avoid "an irreversible injustice."

"If the jury had known what we know now, they never would have convicted Mr. Glossip," Knight said. "It would be a travesty for Oklahoma to move forward with the execution of an innocent man."

--Editing by Karin Roberts.

Update: This story has been updated to include Glossip's application for stay of execution filed with the U.S. Supreme Court.