"Using an inert gas will be effective, simple to administer, easy to obtain and requires no complex medical procedures", Oklahoma Attorney General Mike Hunter said.
Mr. Hunter, the attorney general, said studies described those who had been exposed to "excessive amounts" of inert gas as feeling "fatigue, dizziness, perhaps a headache, loss of breath and eventual loss of consciousness".
A bill signed in 2015 designated nitrogen hypoxia as the state's backup method if lethal injection is unavailable.
Unknowns remain, give that state officials only recently began developing the protocols.
"I believe in justice for victims and their families, and in capital punishment as appropriate for dealing with those who commit these crimes", Hunter said at a news conference, adding he talked to families of murder victims about the decision.
Oklahoma's announcement follows years of national turmoil about execution drugs, including pitched legal battles and resistance from pharmaceutical companies that have questioned whether their products should be used in death chambers.
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Since then, several top officials connected to the bungled executions have resigned and the state's multicounty grand jury delivered a scathing report on Oklahoma's lethal injection process that accused a number of individuals involved in the process of sloppy and careless work.
Death penalty opponents are already expressing skepticism about the use of nitrogen and demanding that Oklahoma be transparent as it preps a new protocol. "I think that Oklahoma has acted first and thought second in the manner it's gone about conducting executions", he told the Post at the time.
Now states are being forced to use new drug cocktails, scramble to restock their stores of drugs and review their lethal injection policies.
The last execution in Oklahoma was that of Charles Warner, who died by lethal injection in January 2015. Nevada and Nebraska also pushed recently to carry out the country's first fentanyl-assisted executions, seizing on the powerful synthetic painkiller that has helped drive the opioid epidemic nationwide.
Hunter said the administration of the gas would probably require the use of a mask placed over the inmate's head, but he said the mechanical details still have to be worked out. When nitrogen gas was approved as a backup method in Oklahoma, the corrections department said there was no protocol in place, and that remained the case Wednesday, almost two years later. "Trying to find alternative compounds or someone with prescribing authority willing to provide us with the drugs is becoming exceedingly hard, and we will not attempt to obtain the drugs illegally".