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.

The execution took place at the William C. Holman Correctional Facility in southern Alabama, where 50-year-old Carey Dale Grayson met his fate. Grayson was part of a group of four teenagers found guilty of murdering Vickie DeBlieux, a 37-year-old hitchhiker, who was traveling to her mother’s home in Louisiana, when she was abducted, brutally assaulted, and thrown from a cliff in 1994, according to the Associated Press.

Grayson was defiant as he was put to death on Thursday evening, making obscene gestures with his hands and hurling expletives at the warden, seemingly having no remorse for his crimes. He also convulsed as he was administered the nitrogen gas before periodically gasping for breath. After ten minutes, Grayson had died from the lack of oxygen.

His death sentence was carried out just hours after the U.S. Supreme Court turned down his motion for a stay. The final appeal filed by his attorneys called for more scrutiny of using nitrogen gas, saying that the method is inhumane because it causes “conscious suffocation.”

“I would submit to the court that being conscious and being suffocated for a period of time constitutes terror,” an attorney with the Federal Defenders Program, John Palombi, told judges during a previous appellate court hearing earlier this week.

Alabama introduced nitrogen gas in 2018 as an alternative execution method from the electric chair and lethal injection. The procedure involves fitting a gas mask over the inmate’s face and flooding it with pure nitrogen, effectively replacing breathable air. Death occurs due to oxygen deprivation, a process known as hypoxia. It’s the first new execution method used in America since 1982 when the lethal injection method was introduced.

The state of Alabama is the third state, along with Oklahoma and Mississippi, to authorize the use of nitrogen gas but has been the only one to carry out executions under the method. Alabama conducted two others this year before Grayson.

State officials have maintained that the nitrogen method is humane.

“Yes, nitrogen hypoxia deprives the condemned inmate of oxygen, but it is not suffocation in the lay sense, like drowning or smothering with a plastic bag or paralyzing the lungs. This is really apples and oranges,” the deputy solicitor general for Alabama, Robert Overing, told the appellate panel, adding that Grayson’s lawyers were trying “to evoke a sense of fear and pain that doesn’t exist with this method.”

Numerous press witnesses, including a reporter from the Associated Press, testified before the court and recounted how both condemned men in the previous executions had shaken on the gurney for more than two minutes before periods of labored breathing with long pauses in between.

Anti-death penalty protesters had gathered outside the court during the hearing earlier this week to speak out against Grayson’s death sentence.

“There is an absolute error in this protocol. It is torturous. It should not be allowed to happen in a civil society,” Amnesty International’s death penalty abolition coordinator for Alabama, T.J. Riggs, told the Associated Press.

The victim’s daughter, Jody Haley, who was 12 when DeBlieux was murdered, attended the execution. While speaking with reporters afterward, she expressed equal parts sorrow for the death of her mother and for Grayson.

“She was unique. She was spontaneous. She was wild. She was funny. She was gorgeous to boot,” Ms. Haley said of her mother before mentioning the murderer’s history of enduring abuse in his youth.

“Society failed this man as a child, and my family suffered because of it,” she said.

“Murdering inmates under the guise of justice needs to stop,” she added. “No one should have the right to take a person’s possibilities, days, and life.”