Inmate sentenced to death in Alabama Carey Dale Grayson should be executed on Thursday with nitrogen gas − a controversial method of which some witnesses described as torture.

If Grayson’s execution moves forward, he will only become the third inmate in the United States, never performed by nitrogen gas hypoxia. The other two such executions also took place in Alabama earlier this year.

Grayson would also become the 22nd inmate executed in the United States so far this year.

Carey Dale Grayson, now 49, was one of four teenagers convicted of capital murder for the torture, bludgeoning and mutilation of Vickie Lynn Deblieux on February 21, 1994. Deblieux, 37 , was hitchhiking from southeast Tennessee to visit his mother in West Monroe. , Louisiana, when the four teens picked her up along a highway near Trussville and soon after proceeded to kill her, according to court records.

Here’s what you need to know about execution.

What was Carey Dale Grayson convicted of?

On February 21, 1994, Deblieux was dropped off by a friend in Chattanooga, near Interstate 59, where she began making trips southwest. At one point, Grayson – who was 19 – and three other teenagers picked up Deblieux. along a highway in Jefferson County, Alabama, about 15 miles northeast of Birmingham.

The teens stopped in a wooded area of ​​Bald Mountain and began beating, stomping and kicking Deblieux. Testimony showed Grayson and another teen held on to her throat to kill her.

Her body was eventually thrown off a cliff, but the teens later returned and mutilated her corpse, cutting the body at least 180 times, removing part of one lung and cutting off her fingers, according to court records .

The teenagers became suspects in the murder when one of the boys showed a friend a Deblieux finger.

Besides Grayson, a jury found Kenny Loggins, Trace Duncan and Louis Mangione guilty of the murder. Duncan, Loggins and Mangione had their death sentences overturned and were each sentenced to life in prison without the possibility of parole. This decision was made in 2005 after the United States Supreme Court banned the execution of people under the age of 18 for committing a crime.

When and where does the execution take place?

The execution is scheduled to begin Thursday, Nov. 21, at 6 p.m. at the Holman Correctional Center in Atmore, about an hour northeast of Mobile. The prison will release Grayson’s last meal and final words after his execution.

How is Carey Dale Grayson executed?

Grayson will be killed by nitrogen hypoxia, which was first used in the United States during the Alabama execution. Kenneth Eugene Smith in January. Smith’s execution by this method attracted national and international scorn as well as media attention, including a protest from the Vatican.

Smith appeared to writhe and convulse on the gurney for at least four minutes during the execution. State and prison officials said before the execution that Smith was expected to lose consciousness “within seconds” and be dead within minutes after gas began flowing into the full face mask Smith was wearing.

Alabama Department of Corrections Commissioner John Q. Hamm called Smith’s execution “textbook” during a news conference about a half-hour after Smith’s death.

With the nitrogen hypoxia method, the convict breathes pure nitrogen through a mask which displaces oxygen in their system. Proponents claim that it is an almost instant and painless method. Opponents say the method is untested and amounts to torture.

On September 26, Alan Eugene Miller became the second Alabama inmate executed with nitrogen hypoxia as a method.

What could stop Carey Dale Grayson from being executed?

Grayson filed several appeals over the years and lost. His last hope for a reprieve rests with the U.S. Supreme Court and Republican Gov. Kay Ivey, who responded to a question from the Montgomery Advertiser about the timing of Grayson’s execution the week before Thanksgiving by saying, “Carey Grayson Did he consider the issue of Grayson’s execution? that he robbed Vicki DeBlieux and her family of now 30 Thanksgivings?”

Smith’s lawyers argued that the nitrogen method could amount to cruel and unusual punishment since it did not guarantee a painless death for their client.

Who is Carey Dale Grayson?

Grayson suffers from bipolar disorder and his mother died when he was 3 after struggling with mental illness, according to court records.

A forensic psychologist testified that Grayson was “in a manic state” during the killing but that he “knew the difference between right and wrong and was capable of appreciating the nature and quality or wrongfulness of his actions, according to court records.

During an interview with police, Grayson described the young teens as committing the most heinous acts during the crime. When asked why they killed Deblieux, according to court records, he told police he didn’t know and that “it wasn’t his problem.”

This article was originally published on USA TODAY: Carey Dale Grayson to be executed with nitrogen gas: what you need to know.