Oklahoma is set to resume the death penalty after a six-year pause with the execution of 60-year-old John Marion Grant, who stabbed a prison cafeteria worker to death in 1998, on Thursday

The state had paused administering lethal injections in 2015 due to a series of flawed executions.

The state was moving forward with Grant’s lethal injection after the US Supreme Court lifted stays of execution that were put in place on Wednesday for Grant and another death row inmate, Julius Jones, by the 10th US Circuit Court of Appeals.

Grant was serving a 130-year prison sentence for several armed robberies at the Dick Conner Correctional Center in Hominy when witnesses say he dragged prison cafeteria worker Gay Carter, 58, into a mop closet and stabbed her 16 times with a homemade shank. He was sentenced to death in 1999.

The state’s Pardon and Parole Board twice denied Grant’s request for clemency, including a 3-2 vote this month to reject a recommendation that his life be spared.

Oklahoma has historically had one of the nation’s busiest death chambers, but a series of problematic lethal injections in 2014 and 2015 led to a de facto moratorium. Richard Glossip was just hours away from being executed in September 2015 when prison officials realized they received the wrong lethal drug. It was later learned the same wrong drug had been used to execute an inmate in January 2015.

The drug mix-ups followed a botched execution in April 2014 in which inmate Clayton Lockett struggled on a gurney before dying 43 minutes into his lethal injection — and after the state’s prisons chief ordered executioners to stop.

While the moratorium was in place, Oklahoma moved ahead with plans to use nitrogen gas to execute inmates, but ultimately scrapped that idea and announced last year that it planned to resume executions using the same three-drug lethal injection protocol that was used during the flawed executions. The three drugs are: midazolam, a sedative, vecuronium bromide, a paralytic, and potassium chloride, which stops the heart.

Oklahoma prison officials recently announced that they have confirmed a source to supply all the drugs needed for seven executions that are scheduled to take place through March.

“Extensive validations and redundancies have been implemented since the last execution in order to ensure that the process works as intended,” the Department of Corrections said in a statement.

More than two dozen Oklahoma death row inmates are part of a federal lawsuit challenging the state’s lethal injection protocols, arguing that the three-drug method risks causing unconstitutional pain and suffering. A trial is set for early next year.

(With AP inputs)