An Alabama inmate found guilty of murdering a hitchhiker 30 years ago on Thursday became the third person in America to be executed using nitrogen gas, furthering the ongoing debate about whether the method is an inhumane way to carry out death penalty sentences.

Carey Dale Grayson, 50, was executed at the William C. Holman Correctional Facility in southern Alabama. He was one of four teens convicted of killing Vickie Deblieux, 37, as she was hitchhiking through Alabama on the way to her mother’s home in Louisiana.