The conviction and death sentence for Oklahoma death row inmate Richard Glossip should be thrown out and a new trial ordered, the state's new attorney general said Thursday, as support has grown even among death penalty supporters who say Glossip is innocent.

In a filing with the Oklahoma Court of Criminal Appeals, Attorney General Gentner Drummond said that although the state is not suggesting Glossip is innocent, the key witness against Glossip lied to the jury about his psychiatric treatment and reasons for taking the mood-stabilizing drug lithium.

That information was only recently disclosed to Glossip's defense team after Drummond turned over a box of evidence, consisting largely of prosecutors' notes in the case, that Drummond's predecessor, John O'Connor, had previously designated as "work product."

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"After thorough and serious deliberation, I have concluded that I cannot stand behind the murder conviction and death sentence of Richard Glossip," Drummond said in a statement. "This is not to say I believe he is innocent. However, it is critical that Oklahomans have absolute faith that the death penalty is administered fairly and with certainty. Considering everything I know about this case, I do not believe that justice is served by executing a man based on the testimony of a compromised witness."

Glossip was convicted of the 1997 murder-for-hire killing of his boss, motel owner Barry Van Treese, at two separate trials based largely on the testimony of his co-defendant, Justin Sneed. Sneed admitted robbing and killing Van Treese, but claims he only did so after Glossip agreed to pay him $10,000. Sneed received a sentence of life in prison.

The Oklahoma Court of Criminal Appeals must decide whether to vacate Glossip's conviction and order a new trial. Glossip is scheduled to be executed on May 18.

Glossip's attorneys did not immediately respond to a request for comment.