ON JANUARY 25TH Kenneth Eugene Smith became the first person anywhere to be executed by nitrogen hypoxia. He was convicted in 1989 of murdering Elizabeth Sennett, the wife of a preacher from Alabama, on her husband’s orders. The state had first tried to execute him, by lethal injection, in November 2022, but botched the procedure. After that, Mr Smith chose to be put to death by novel means. His execution has caused outrage: Alabama claims nitrogen hypoxia is a quick, painless death but many medical experts disagree. Some have likened it to torture. Why did Alabama authorise this untested method?

Lethal injection was used for 89 of the 92 executions carried out in America between 2019 and 2023. (The remaining three were by electric chair.) Three drugs are typically used: an anaesthetic, a paralytic and a chemical that stops the heart. But in recent years a number of American pharmaceutical companies have stopped supplying these drugs because they do not want to be associated with the death penalty. The European Union has banned the export of any drug that could be used in an execution. Some American states are seeking alternatives. Five (most recently Idaho in 2023) have approved execution by firing squad, a method last used in Utah in 2010. And three—Alabama, Mississippi and Oklahoma—have authorised the use of nitrogen gas.

Nitrogen makes up 78% of the air. But it is only safe to inhale when mixed with oxygen. During an execution the inmate breathes pure nitrogen through a mask, causing asphyxiation. Research on death by nitrogen exposure is limited: most of what is recorded in medical journals relates to accidents or suicide attempts. Some studies of oxygen deprivation suggest that it can cause pain similar to that of a heart attack. Nitrogen hypoxia may cause the prisoner to defecate or vomit while remaining conscious. The American Veterinary Medical Association wrote in its euthanasia guidelines in 2020 that nitrogen hypoxia is not an acceptable euthanasia method for most mammals because it is “distressing”. Moreover, if a prisoner’s mask is not placed correctly, nitrogen could leak, putting other people in the room, such as a spiritual adviser, at risk.

Several weeks before Mr Smith’s execution, the UN Office of the High Commissioner for Human Rights warned that the procedure could amount to torture. But America’s Supreme Court rejected a last-minute bid by the prisoner’s legal team to halt his execution. According to witnesses, Mr Smith was conscious for several minutes after the procedure had begun, and seemed to be in extreme pain. “What we saw was minutes of someone struggling for their life,” said the Reverend Jeff Hood, Mr Smith’s spiritual adviser. Those present say it took 22 minutes for Mr Smith to die.

Alabama has an especially unhappy history of executions. Like many states, it has struggled to recruit highly trained medical staff to administer lethal injections: both the American Medical Association and the American Board of Anesthesiology ban their members from participating. The first attempt to execute Mr Smith was called off after staff struggled to put an intravenous line into his arm. That was the third consecutive execution attempt in which Alabama officials had problems administering lethal injections. (One other inmate survived the procedure; the other died after a three-hour ordeal, the longest in American records.) On January 26th Alabama’s attorney-general, Steve Marshall, said that 43 other prisoners have chosen to be executed by nitrogen hypoxia, rather than endure a lethal injection. That will not guarantee a swift or painless death. ■