Nitrogen Hypoxia: What to Know About This New Method of Execution

The planned execution of a death row inmate by the state of Alabama on Thursday evening will be carried out by a procedure that has never been used for capital punishment in the United States.

The inmate, Kenneth Smith, who was convicted in a 1988 stabbing murder, will be put to death by inhaling nitrogen gas, a method known as nitrogen hypoxia.

Supporters of the method say it is fast and painless. But earlier this month, the United Nations Human Rights Office urged Alabama to stop the execution, saying it could amount to torture and be in violation of human rights treaties that the United States has agreed to.

Alabama would be the first state to use nitrogen hypoxia, but other states are interested in employing the method.

What is nitrogen hypoxia?

Hypoxia is a medical term for a state of insufficient oxygen in the body. Nitrogen, a colorless, odorless gas, makes up about 78 percent of the air inhaled by humans. But under the method of nitrogen hypoxia, the person breathes in only nitrogen, leading within minutes to unconsciousness and then death from lack of oxygen.

How will the nitrogen be administered?

According to the protocol released by Alabama prison officials, members of the “execution team” will strap Mr. Smith to a gurney in the state’s execution chamber in Atmore. A mask will be placed on his head and nitrogen will be released into it, depriving him of oxygen. Many experts compare this process to putting a plastic bag over someone’s head, although in that situation, the person would be inhaling carbon dioxide rather than nitrogen.