Attorneys for an Oklahoma death row inmate are making a last-minute effort to spare their client's life just hours before his scheduled execution, arguing they have new evidence to support his claim that he was framed.

Richard Eugene Glossip's attorneys asked the Oklahoma Court of Criminal Appeals late Tuesday to stop his lethal injection, saying they uncovered new details in the case, including a signed affidavit from an inmate who served time with Justin Sneed, who also was convicted of the killing and is serving a life sentence.

"We're asking for a stay of execution to give the court more time to review this new evidence, which we think casts grave doubt on Richard's guilt," said Mark Henricksen, one of Glossip's attorneys.

Glossip, 52, is scheduled to be executed Wednesday afternoon at the Oklahoma State Penitentiary in McAlester. He was convicted of ordering the 1997 beating death of Barry Van Treese, who owned the motel where Glossip worked.

Sneed was the prosecution's key witness and testified that Glossip masterminded the killing because he was afraid Van Treese was about to fire him for embezzling money and poorly managing the motel. Sneed was sentenced to life in prison in exchange for his testimony.

A fellow inmate, Michael Scott, said in an affidavit that he heard Sneed say "he set Richard Glossip up, and that Richard Glossip didn't do anything."

Glossip maintained his innocence Tuesday in a brief telephone interview with The Associated Press and said he remains optimistic his lethal injection will be halted.

"They'll never take that from me," Glossip said. "I'll hope for the best. I won't let it bring me down.

"If you've got to go out... you don't want to be bitter and angry about it."

Glossip's case has drawn attention from death penalty opponents, and his family and supporters rallied Tuesday at the Oklahoma Capitol. They want Republican Gov. Mary Fallin to issue a 60-day stay to give Glossip's attorneys more time to investigate new leads.

But the governor said in a statement Wednesday that she remains convinced of Glossip's guilt, and "after carefully reviewing the facts of this case multiple times" has no plans to issue a stay.

Among his supporters is Hollywood actress Susan Sarandon, who played a nun in the movie "Dead Man Walking." The woman Sarandon portrayed, anti-death penalty advocate Sister Helen Prejean, serves as Glossip's spiritual adviser and plans to attend his execution Wednesday.

Oklahoma County District Attorney David Prater, whose office prosecuted Glossip before Prater was elected, said he's reviewed boxes of evidence and is convinced of Glossip's guilt.

"Mr. Van Treese would not be dead but for Mr. Glossip offering what Mr. Sneed thought was half of $10,000 to kill Barry Van Treese," Prater said. "(Glossip) set everything into motion."

Van Treese's wife, Donna, wrote in a letter to Oklahoma's Pardon and Parole Board last year that the loss of her husband has been devastating to her and her family.

"As the wife, I lost the most important person to me: my husband and the father to my children," Donna Van Treese wrote. "I have had a very hard time just moving on one day at a time, and physically I have been under more stress than any one person should endure in a lifetime."

Glossip's execution is scheduled for 3 p.m. Wednesday. Department of Corrections spokeswoman Terri Watkins said the time was moved from 6 p.m. so the process didn't disrupt a shift change and meal time at the facility, and so that media and execution witnesses would be off the prison grounds before dark.

___

Follow Sean Murphy at www.twitter.com/apseanmurphy