On Jan. 25, Kenneth Eugene Smith was the first person in Alabama, indeed the first person in the United States, to be executed by nitrogen gas hypoxia. This was Alabama’s second crack at Smith, who was convicted of a 1988 murder-for-hire. He had been the subject of a botched execution in 2022 that was called off after he spent four hours on a gurney while the authorities tried unsuccessfully to correct an IV line.

In theory, the way nitrogen gas hypoxia works is that when nitrogen gas is introduced there is not enough oxygen left to sustain bodily functions. In court filings, Alabama represented that the nitrogen gas would cause unconsciousness “within seconds” and death “within minutes.” The continuous-flow air respirator mask, which creates a seal over the wearer’s face, is the vehicle for providing the nitrogen gas.