However, medical and legal experts told ABC News that nitrogen gas as a method for execution is untested and there’s no evidence the method will be any more humane or painless than lethal injection.

“I’ve never heard anyone say, ‘We’ve got this new method of execution. We’ve looked at it carefully. We know that this method of execution will cause a death that will not be cruel. Here’s the evidence,’” Dr. Joel Zivot, an associate professor in the department of anesthesiology at Emory University School of Medicine, told ABC News. “That’s what needed to be said. No one has said that.”