Carey Grayson was executed using controversial method after being convicted of the 1994 murder of a hitchhiker.
A man convicted of murdering a hitchhiker 30 years ago has become the third person in the United States to be executed by nitrogen gas.
Carey Grayson, 50, was executed in Alabama on Thursday after the US Supreme Court declined a request for a stay on the grounds that asphyxiation by nitrogen gas constitutes cruel and unusual punishment.
Grayson was sentenced to death over the 1994 torture, bludgeoning and mutilation of Vickie Lynn Deblieux, a hitchhiker who was travelling to her mother’s home in Louisiana.
Deblieux’s mutilated body was found with 180 stab wounds, one of her lungs removed and her fingers and thumbs cut off.
“Tonight, justice has been served,” Alabama Attorney General Steve Marshall said in a statement.
Alabama has executed three death row inmates by nitrogen gas this year and is the only US state to have employed the controversial method.
While Alabama officials have described nitrogen asphyxiation as the most painless and humane method of execution, critics have likened the practice to torture.
During his execution, Grayson shook his head from side to side, pulled against his gurney restraints and gasped for several minutes before being pronounced dead, according to US media reports.
Alabama Department of Corrections Commissioner John Q Hamm said after the execution that Grayson’s movements appeared to have been “for show”.
A group of United Nations experts on Thursday called for a ban on execution by nitrogen gas, saying it violates international law.
“We emphasise that the prohibition on torture or to cruel, inhuman or degrading treatment or punishment is absolute, never acceptable and not dependant on alternatives,” the experts said in a statement released by the Office of the UN High Commissioner for Human Rights.
Out of 50 US states, 21, including Florida, Louisiana, Mississippi and Georgia, allow the death penalty.
So far this year, US authorities have executed 22 people.