The Associated Press
This file photo provided by the Oklahoma Department of Corrections shows death row inmate Richard Glossip. The Oklahoma Court of Criminal Appeals has set execution dates for three death row inmates who had challenged a drug that will be used in their lethal injections. Execution dates of Sept. 16, 2015 for 52-year-old Glossip, Oct. 7, 2015 for 50-year-old Benjamin Robert Cole, and Oct. 28, 2015 for 54-year-old John Marion Grant have been scheduled.

OKLAHOMA CITY — Oklahoma's highest criminal court on Wednesday set execution dates for three death row inmates who challenged the use of a drug that will be used in their lethal injections.

The Oklahoma Court of Criminal Appeals set execution dates of Sept. 16 for 52-year-old Richard Eugene Glossip, Oct. 7 for 50-year-old Benjamin Robert Cole, and Oct. 28 for 54-year-old John Marion Grant.

The three inmates had argued that the state's planned use of the sedative midazolam risked subjecting them to pain and suffering because it doesn't properly render a person unconscious. But the U.S. Supreme Court ruled last month in a 5-4 decision that the drug can be used in executions without violating the Eighth Amendment prohibition on cruel and unusual punishment.

Terri Watkins, a spokeswoman for the Oklahoma Department of Corrections, said Wednesday that the state has access to the drugs needed to carry out all three executions and is prepared to proceed.

An attorney for the inmates maintained in a statement Wednesday that scientific information about midazolam and its use in previous problematic executions shows that it can't maintain anesthesia throughout the execution procedure.

"Because Oklahoma plans to use a paralytic as part of the lethal injection formula, we will never know if prisoners will suffer during the execution process," said attorney Dale Baich.

The three inmates challenged the use of midazolam after Oklahoma used it in last year's botched execution of Clayton Lockett. Lockett, a convicted murderer who was the first Oklahoma inmate to be put to death with the drug, writhed and moaned on the gurney before state officials tried to halt the execution midway through it. He died anyway 43 minutes after the execution began.

Midazolam also was used in executions that took longer than usual in Arizona and Ohio last year.

Oklahoma increased by five times the amount of midazolam it used in the January execution of Charles Warner, who complained of a burning sensation but showed no other obvious signs of physical distress.

Glossip was convicted of first-degree murder in the 1997 beating death of Barry Alan Van Treese at a west Oklahoma City motel. A co-defendant confessed to beating Van Treese, but said he did so at Glossip's direction. Glossip has maintained his innocence.

Grant was sentenced to die for the 1998 stabbing death of Gay Carter, a prison worker at the Dick Connor Correctional Center in Hominy. Prosecutors say Grant dragged Carter into a mop closet and stabbed her 16 times with a pick-like shank.

Cole was convicted of first-degree murder in Rogers County for the December 2002 beating death of his 9-month-old daughter, Brianna Cole.

Glossip and Grant both already have been denied clemency by the Oklahoma Pardon and Parole Board. A clemency hearing for Cole has not been set.

Follow Sean Murphy at