A death row inmate convicted of killing a 78-year-old Savannah woman is set to become the first person in Georgia executed using a new lethal injection drug.

Roy Willard Blankenship is scheduled to be put to death at 7 p.m. Thursday for the 1978 killing of Sarah Mims Bowen, who died of heart failure after she was raped in her Savannah apartment.

His attorneys challenged Georgia's decision to swap the sedative sodium thiopental for pentobarbital as part of its three-drug execution combination. The state was forced to make the switch after federal regulators launched an investigation into how Georgia obtained sodium thiopental.

Wednesday, a Fulton County judge briefly delayed the process as she considered the defense challenge.

Blankenship's attorneys claim pentobarbital is an untested and unsafe chemical that could cause him to needlessly suffer. State attorneys say those claims are unfounded.

Tags: Georgia, death row inmate, execution, Roy Willard Blankenship, lethal injection drug