Kenneth Smith becomes 1st person in US to be executed by nitrogen gas

An Alabama man was executed Thursday evening becoming the first person in the United States to die via nitrogen gas, according to Gov. Kay Ivey.

Kenneth Smith, 58, who was sentenced to death for his role in the 1988 murder-for-hire plot of a preacher's wife, was originally set to be executed in November 2022 with a lethal injection, but officials were unable to locate a vein and were forced to call it off.

"The execution was lawfully carried out by nitrogen hypoxia, the method previously requested by Mr. Smith as an alternative to lethal injection. At long last, Mr. Smith got what he asked for, and this case can finally be put to rest," the governor said in a statement Thursday evening.

"I pray that Elizabeth Sennett's family can receive closure after all these years dealing with that great loss," Ivey said.

The execution took place at 8:25 p.m.

The United States Supreme Court denied Smith's last-ditch appeal on Thursday, asking for a stay of the execution, which was set for 7 p.m. ET.

He and his attorneys had argued that execution by nitrogen gas would constitute cruel and unusual punishment under the 8th Amendment and that he "is suffering mentally and physically from the posttraumatic stress" of the botched execution attempt, documents show.

Smith was one of three people in Alabama whose executions were botched in 2022, according to the Death Penalty Information Center, a non-profit that provides data and analysis on capital punishment.

The Supreme Court rejected a previous appeal Wednesday evening, allowing Alabama officials to proceed with the execution.

Alabama is one of three states, including Mississippi and Oklahoma, that allows nitrogen gas to be used as a method of execution, but it has never been carried out before.

Nitrogen hypoxia is the term for a means of death caused by breathing in enough nitrogen gas to deprive the body of oxygen -- in this case, intended to be used as a method of execution.

The protocol in Alabama calls for an inmate to be is strapped to a gurney and fitted with a mask and a breathing tube. The mask is meant to administer 100% pure nitrogen, depriving the person of oxygen until they die.

Although 78% of the air humans breathe is made up of nitrogen, if the concentration of nitrogen is too high and of oxygen too low, the body's organs are deprived of oxygen, which they need to function, and begin shutting down, causing a person to die, according to the U.S. Chemical Safety Board.

In previous court appeals, nitrogen hypoxia was among the methods Smith's legal team had recommended as a suitable alternative to lethal injection when he was challenging that method as unconstitutional.

In an attempt to get Alabama to halt the execution, Smith argued this form of execution could fail and could cause him to asphyxiate on his own vomit, suffer a stroke or be left in a vegetative state.

Numerous organizations, including the U.N. Human Rights Office and the Vatican-affiliated Catholic charity Sant'Egidio Community, have called on Alabama to call off the execution, with the latter referring to the planned nitrogen gas method as

"This method has been thoroughly vetted, and both the Alabama Department of Corrections and the Attorney General's Office have indicated it is ready to go," Gov. Kay Ivey said in a statement to ABC News on Thursday. "The Legislature passed this law in 2018, and it is our job to implement it. I am confident we are ready to move forward."

ABC News' Devin Dwyer contributed to this report.

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