ATLANTA — Georgia prison officials violated state administrative procedures by failing to hold a public notice hearing before they changed the state’s execution procedure, a lawyer for a death row inmate argued before the state’s highest court Monday.

The switch in July from a three-drug combination to a single-drug method was not preceded by a 30-day notice period as required by the Georgia Administrative Procedure Act, which means the new method is invalid, argued Lisa Heller, an attorney for Warren Lee Hill. It was announced a day before Hill had been scheduled to be executed.

A lawyer for the state countered that the injection protocol should not be considered a rule that is subject to that law. The lethal injection protocol is part of the Department of Corrections’ standing operating procedures that can be changed by the department commissioner without additional steps, Joseph Drolet said.

Hill was convicted in the August 1990, beating death of fellow inmate Joseph Handspike. Hill was serving a life sentence at the time for the shooting death of his 18-year-old girlfriend. he was convicted in 1991 on charges of malice murder, felony murder and aggravated assault in Handspike’s death and was sentenced to death.

Hill was set to be executed July 18. The day before, the Department of Corrections announced the change in its execution protocol and delayed Hill’s execution until July 23.

Hill’s lawyers challenged the new execution protocol and, just a few hours before Hill was to be executed, the Georgia Supreme Court stayed the execution to give itself time to determine whether corrections officials broke the law. Both sides presented oral arguments before the high court Monday.