A death row inmate in Alabama is scheduled to be executed on Thursday using nitrogen gas, a method vets have deemed too cruel for animals.
Kenneth Eugene Smith, 58, has been on death row for more than three decades after being convicted in 1989 of a murder-for-hire.
He is to be executed by nitrogen hypoxia, a first in the United States, and a method which the United Nations has likened to “torture”.
Smith is to be put to death at Holman Prison in Atmore, Alabama, during a 30-hour window beginning at 12am local time (6am GMT) on Thursday.
The controversial method was proposed after Smith was subjected to a botched execution attempt in 2022 by lethal injection.
Prison officials were unable to set intravenous lines to administer the injection.
The last US execution using gas was carried out in 1999 when a convicted murderer was put to death using hydrogen cyanide gas.
How nitrogen hypoxia works
Alabama is one of three US states that have approved the use of nitrogen hypoxia as a method of execution. It involves administering nitrogen gas through a facemask, depriving the body of oxygen.
Ravina Shamdasani, a spokeswoman for the UN rights office in Geneva, urged Alabama last week to abandon plans to execute Smith using the “novel and untested” method.
Ms Shamdasani said it could “amount to torture or other cruel, inhuman or degrading treatment or punishment, under international human rights law.”
While nitrogen gas has never been used to execute humans in the US, it is sometimes used to kill animals.
But even the American Veterinary Medical Association has advised against using nitrogen gas to euthanise most mammals, calling it “distressing”.
Experts have repeatedly warned that nitrogen toxicity may cause a person to suffer unnecessarily, while at the same time threatening the health of others in the room.
Alabama’s protocol for execution by nitrogen asphyxiation makes no provision for sedation prior to execution.
Smith was convicted of the 1988 murder of Elizabeth Sennett, a pastor’s wife.
