Experts with the United Nations are concerned about the execution of an Alabama man, who murdered a woman in the late 1980s, being carried out by nitrogen hypoxia.

The group of four experts spoke out regarding Kenneth Smith’s execution, USA Today reported Wednesday.

The U.N. news release continued:

Kenneth Smith, who has been on death row for over three decades, is scheduled to be executed on January 25, 2024, in the U.S. State of Alabama. Authorities in Alabama previously attempted to execute Smith in November 2022 using lethal injection, but the attempt failed.

The recently approved ‘Executions’ Protocol’ of the State of Alabama, allows for the use of nitrogen gas asphyxiation. “We are concerned that nitrogen hypoxia would result in a painful and humiliating death,” the experts said. They warned that experimental executions by gas asphyxiation – such as nitrogen hypoxia – will likely violate the prohibition on torture and other cruel, inhuman or degrading punishment.

In November, the man’s lawyer filed a federal lawsuit to stop the upcoming execution. The Today report noted, “If the execution method proceeds, it would be the first in the United States.”

Smith apparently asked to be executed by nitrogen hypoxia, and the United States Supreme Court sided with him in May, WHNT reported in August.

“Now his request is moving forward,” a reporter for the outlet said at the time:

Per AL.com, Smith was convicted of murdering a woman named Elizabeth Dorlene Sennett on March 18, 1988, the outlet reported in November 2022.

The woman’s husband, a minister with the Church of Christ, was identified as Charles Sennett Sr. When he found her body inside their residence, she had been stabbed multiple times in her chest and one time on both sides of her neck.

The outlet detailed the case:

“The evidence established that Charles Sennett (Sr.) had recruited Billy Gray Williams, who in turn recruited Smith and John Forrest Parker, to kill his wife. He was to pay them each $1,000 in cash for killing Mrs. Sennett,” court documents show.

There also was testimony that Charles Sennett Sr. was involved in an affair, that he had incurred substantial debts, that he had taken out a large insurance policy on his wife, and that approximately one week after the murder, when the murder investigation started to focus on him as a suspect, the minister committed suicide in front of his sons, according to a summary of the case in court documents.

Following his conviction, Parker was executed in 2010. Although Williams was not present when the murder took place, he was sentenced to life without parole and later died in 202o.

According to the Today report, execution by nitrogen hypoxia means a person breathes nitrogen through a mask, which eventually ends their life.

Nitrogen is described as a colorless, odorless, and tasteless gas, according to Britannica.