The Georgia Supreme Court halted the execution of Warren Lee Hill, a death-row inmate who had been scheduled to die at 7 p.m. on Monday at the state penitentiary at Jackson.

At issue is whether the Department of Corrections’ decision to switch to a one-drug formula violates state rules, the Atlanta Journal-Constitution reported. The state announced the change last week, which Hill’s lawyers challenged.

The high court said in a statement Monday that it would consider the challenge because such a change requires public hearings and a 30-day public comment period.

Hill was the first inmate set to be executed in Georgia since the state changed its execution procedure last week from a three-drug injection to a single dose of the sedative pentobarbital.

Hill was convicted in the Aug. 17, 1990, beating death of another inmate. Hill was serving a life sentence at the time for the shooting death of his 18-year-old girlfriend.

His lawyers argue that Hill is mentally disabled – significant because federal law prohibits states from executing the mentally disabled. But the state said the defense hadn’t conclusively shown that Hill has a mental disability.

On July 18, Yokamon Hearn, 33, became the first prisoner killed with the one-drug formula. Texas Department of Criminal Justice officials announced last week they were modifying the three-drug injection method used since 1982 because the state's supply of one of the drugs — the muscle relaxant pancuronium bromide — has expired.