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A New Execution Method May Soon Be Used In US, And Some Are Concerned

Some argue nitrogen hypoxia is a painless way to kill, but critics fear there's not enough evidence.


Tom Hale

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

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Lethal injection metal prison chair in the cell for death sentence

Alabama, Oklahoma, and Mississippi have authorized the use of nitrogen hypoxia as an execution method, but no state has performed an execution using it yet.

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A new execution method could potentially soon be used for the first time in the US: nitrogen hypoxia. While its proponents argue it is a humane and effective means of capital punishment, its critics say there’s simply not enough evidence to justify its use.

Nitrogen hypoxia involves forcing a person to breathe pure nitrogen gas, starving them of oxygen until they die. Although the exact protocols have not yet been drawn up, there is some idea of what they might entail:


“The protocol would likely involve placing some type of mask over the condemned inmate’s head and pumping it full of 100 percent nitrogen, thereby depriving that person of oxygen. The inmate would die not by suffocation, which is caused by an inability to exhale and a subsequent (and very painful) buildup of carbon dioxide in the body, but rather by becoming gradually oxygen-deprived, which is essentially painless,” according to The Marshall Project, a criminal justice NGO.

Just three US states have authorized the use of nitrogen hypoxia as an execution method – Alabama, Oklahoma, and Mississippi – but no state has performed an execution using it, according to the Death Penalty Information Centre.

That could soon change, however. 

The experimental execution method has recently made the news because of the unusual case of Kenneth Eugene Smith, an Alabama inmate who was sentenced to death for a 1988 murder-for-hire. Together with accomplice John Parker, Smith was hired to kill Elizabeth Dorlene Sennett by her husband so he could collect her life insurance.


Smith was set to die in November 2022, but he survived after prison authorities couldn’t find an intravenous line for the lethal injection drugs before the state’s execution warrant expired at midnight.

Following the botched execution, his legal team had argued in federal court that he should be allowed to die by nitrogen hypoxia, alleging that attempting another lethal injection would subject him to cruel and unusual punishment in violation of the US Constitution's 8th Amendment. 

After Smith won his case at the lower court level, Alabama officials appealed to the US Supreme Court (SCOTUS). However, on Monday, May 15, the SCOTUS allowed Smith's challenge to proceed.

Despite Smith’s desire to receive this method of execution, experts have previously expressed concern that the method hasn’t undergone enough testing and research. 


“There is a claim, that I think is baseless, that nitrogen gas inhalation would cause a death that would be peaceful and not cruel. There’s no evidence for any of that,” Joel Zivot, an associate professor of anesthesiology at Emory University, told Scientific American in 2022. 

Research on nitrogen hypoxia in non-human mammals has led veterinarians and animal health regulators to conclude that the method is unacceptable for euthanizing animals. Some studies have shown that dogs take up to five minutes to die despite losing consciousness within one to two. For larger-bodied humans, it could take even longer.

Older studies, however, have found the opposite, concluding that nitrogen hypoxia is "effective, humane, safe, and economically feasible as a method of euthanasia."

Some also contend that it is notably more humane than lethal injection, which has been linked to a number of botched executions


“It’s a painless way to go. But more time needs to be spent [studying] that," Louisiana Department of Corrections Secretary James LeBlanc told the state legislative committee in April 2014.

In sum, there’s not enough evidence to make an informed judgment either way. It’s even unclear how this could be ethically tested and assess how humane this method of dying is. 

Despite these many ethical and practical questions, the US may become the first country in the world to officially use nitrogen in an execution chamber if these legal proceedings continue to drive the way they are going. 


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