In what would be the nation's first attempt to execute a death row inmate using nitrogen gas, Alabama has set a 2024 date to execute a convicted killer using hypoxia.

On Wednesday, Governor Kay Ivey, the first female Republican to hold the office in that state, announced the execution of 58-year-old Kenneth Eugene Smith, will be carried out sometime between Jan. 25 and 6 a.m. on Jan. 26.

Smith was convicted of killing Elizabeth Dorlene Sennett in northern Alabama more than 35 years ago.

"The execution will be carried out by nitrogen hypoxia, the method previously requested by the inmate as an alternative to lethal injection," Ivey spokesperson Gina Maiola wrote in an emailed statement to the Associated Press.

USA TODAY has reached out to Ivey's office.

The governor's decision came less than one week after the Alabama Supreme Court ruled the state can proceed with the new method, the Montgomery Advertiser, part of the USA TODAY Network reported.

Here's what we know:

What is nitrogen hypoxia?

Nitrogen makes up 78% of the air inhaled by humans, according to the U.S Chemical Safety Board, and is harmless when inhaled with proper levels of oxygen.

The approved execution method of nitrogen hypoxia forces the inmate to breathe only nitrogen. The act deprives the inmate of oxygen needed to maintain bodily functions leading to death.

According to the proposed execution protocol, obtained by the Associated Press, a mask is placed over the inmate's nose and mouth and their air is replaced by nitrogen then administered "for 15 minutes or five minutes following a flatline indication."

In Alabama, according to the Death Penalty Information Center, lethal injection remains the state’s primary execution method. Only two other states − Oklahoma and Mississippi − have authorized the use of nitrogen hypoxia, but it has never been used to execute a person on death row.

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Who approved the decision to use nitrogen hypoxia?

In November 2022, the state tried to execute Smith using lethal injection, but the Department of Corrections stopped the execution when the execution team could not get the two intravenous lines connected to Smith.

In August, the Attorney General’s Office filed a motion with the Alabama Supreme Court requesting the court reschedule Smith’s execution date.

On Nov. 1, the Alabama Supreme Court, in a 6-2 decision, allowed the state to proceed with the new execution method on Smith.

That same day, Alabama Attorney General Steve Marshall released a statement saying Sennett’s family had “waited an unconscionable 35 years to see justice served.”

Under the law, the governor sets a person's execution date. Ivey has the authority to grant him clemency before the execution, but she said she does not plan to do so.

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Who is Kenneth Eugene Smith?

As of Thursday, Alabama Department of Correction records showed Smith was one of 164 people on death row in the state.

He is one of two people convicted of killing Sennett.

The 1988 murder-for-hire slaying took place in Colbert County, and also involved Sennett's husband, Charles Sennett. Prosecutors said the debt-ridden preacher was behind the contract killing, which involved Smith.

In 1996, a jury convicted Smith in the plot to murder Sennett and sentenced him to life without the possibility of parole. But a trial judge overrode the jury recommendation and sentenced Smith to death despite the recommendation of life imprisonment from the jury. The state, in 2017, abolished the practice of judicial override.

Smith's attorneys are seeking to stop execution

Smith's attorneys have filed a federal lawsuit seeking to halt the execution, according to the Associated Press, claiming the state is making their client the "test subject for this novel and experimental method."

"Like the eleven jurors who did not believe Mr. Smith should be executed, we remain hopeful that those who review this case will see that a second attempt to execute Mr. Smith − this time with an experimental, never-before-used method and with a protocol that has never been fully disclosed to him or his counsel − is unwarranted and unjust," Smith's attorney Robert Grass wrote in an emailed statement to the AP.

The statement, the AP reported, said jurors at Smith's trial "voted 11-1 to recommend a sentence of life imprisonment, but a judge overrode that recommendation and imposed the death penalty."

When is the next execution in Alabama?

Ivey has also set an execution date for Casey McWhorter, scheduling the execution for a 30-hour window between midnight Nov. 16 and 6 a.m. Nov. 17.

McWhorter was sentenced to death for the murder of Edward Lee Williams. He has filed state and federal appeals claiming the state did not notify him of the planned execution in time.

Contributing: Ralph Chapoco and The Associated Press

Natalie Neysa Alund is a senior reporter for USA TODAY. Reach her at nalund@usatoday.com and follow her on X @nataliealund. Alex Gladden is the Montgomery Advertiser's public safety reporter. She can be reached at agladden@gannett.com or on Twitter @gladlyalex.

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