Alabama performs 1st nitrogen gas execution: What to know about this method

State officials have argued it is a humane and painless form of death.

An Alabama man has become the first ever person executed via a new method, nitrogen gas, on Thursday.

Kenneth Eugene Smith, 58, was sentenced to death for his alleged role in the 1988 murder of Elizabeth Sennett. Her husband, Charles Sennett, allegedly hired someone -- who, in turn, hired two men, including Smith -- to kill his wife and make it look like a burglary gone wrong.

Smith was to be executed in November 2022 via lethal injection, but, despite multiple attempts, officials were not able to insert an intravenous line to administer the drugs before the death warrant expired.

However, medical and legal experts told ABC News that nitrogen gas as a method for execution is untested and there's no evidence the method will be any more humane or painless than lethal injection.

"I've never heard anyone say, 'We've got this new method of execution. We've looked at it carefully. We know that this method of execution will cause a death that will not be cruel. Here's the evidence,'" Dr. Joel Zivot, an associate professor in the department of anesthesiology at Emory University School of Medicine, told ABC News. "That's what needed to be said. No one has said that."

Three states -- Alabama, Mississippi and Oklahoma -- have approved nitrogen gas as a form of execution and Alabama Gov. Kay Ivey defended the method in a statement to ABC News last week.

"Nitrogen hypoxia is the method previously requested by the inmate as an alternative to lethal injection," she said. "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. The Legislature passed this law in 2018, and it is our job to implement it. I am confident we are ready to move forward."

What is nitrogen hypoxia?

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 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.

About 78% of the air that humans breathe is made up of nitrogen gas, which may lead people to believe that nitrogen is not harmful, according to the U.S. Chemical Safety Board.

However, when an environment contains too much nitrogen and the concentration of oxygen becomes too low, the body's organs, which need oxygen to function, begin shutting down and a person dies.

State officials have argued death by nitrogen gas is a humane, painless form of execution and that the person would lose consciousness before they die.

Problems surrounding lethal injection

States and jurisdictions can use a one-, two- or three-drug combination. The three-drug combination involves, firstly, an anesthetic or sedative, then a drug to paralyze the prisoner and, lastly, a drug to stop the heart, the DPIC said.

The one and two-drug method typically use an overdose of an anesthetic or sedative to perform the execution.

Lethal injection was seen as a more humane form of execution that would lead to instantaneous death, Zivot said.

"It replaced the firing squad, it replaced electrocution, it replaced the gas chamber, it replaced hanging, all these kinds of methods are a lot more visual than lethal injection," he said. "It looked like a prisoner was kind of closing their eyes and falling off to sleep and then dying."

However, problems have arisen with lethal injections in the form of botched executions. Officials have struggled to find veins, intravenous lines have clogged with the deadly chemicals and prisoners have had violent reactions to the dispensed drugs.

Additionally, there have been shortages of the drugs used for lethal injection.

"Companies that made the drugs used in the lethal injection, some of them did not want to participate in making drugs for killing people," Jeffrey Kirchmeier, a professor of law at City University of New York School of Law, told ABC News. "So, states, fairly recently. in the last decade or so, began experimenting with different drugs with lethal injection not with a lot of science behind it, but using different drugs that they could access."

In 2016, Zivot was examining autopsy reports of prisoners who were executed via lethal injection and found that the inmates' lungs were twice as heavy as they normally weigh. He asked a colleague at Emory to check, and he found the same thing.

They discovered that prisoners who had received lethal injections were suffering from pulmonary edema, which is when fluid builds up in the lungs, making it difficult to breathe. Further research Zivot conducted with NPR found similar results.

"It seemed to me that this was death akin to drowning," Zivot said. "You are drowning in your own secretions … Lethal injection is actually a myth. The myth is that this is a peaceful death and not a cruel death, and that's just not true."

The controversy surrounding execution by nitrogen gas

"So, [officials] think that it will kill quickly, and that this kind of death will appear to be without suffering, will not be cruel, and that's their claim," Zivot said.

However, Alabama's published protocol has been heavily redacted, which initially made it unclear exactly how the execution would be performed, and officials were not planning to release any documentation of the execution afterward, according to Zivot.

"That's definitely one of the concerns here because so much about executions are done in secrecy," Kirchmeier, who teaches courses that include capital punishment, said. "It's a government act, the government is doing this and so it should be something that people have access to, that the media has access to."

In court, Smith argued there are several ways his execution could go wrong including the mask may not fit properly, or it may dislodge. Additionally, he said the method could cause him to suffer hypoxia short of death, a stroke or leave in him a vegetative state if the method fails.

Kirchmeier also said doctors are not ethically allowed to help with executions including lethal injection or nitrogen gas, so the procedures are not done by doctors with medical expertise.

A court ruled earlier this month that Alabama could proceed with the execution and that it did not find that the method would constitute as "cruel and unusual punishment."

On Wednesday, the Supreme Court declined Smith's last-minute request to halt the execution.

Numerous organizations called on Alabama to stay the execution, including the U.N. Human Rights Office, saying execution via nitrogen gas could be classified as torture and violate international human rights treaties.

"We have serious concerns that Smith's execution in these circumstances could breach the prohibition on torture or other cruel, inhuman or degrading treatment or punishment, as well as his right to effective remedies," Ravina Shamdasani, spokesperson for the U.N. Human Rights Office, said during a press briefing earlier this month,

Additionally, Sant'Egidio Community, a Catholic charity affiliated with the Vatican, made an appeal to Alabama to halt the execution, calling it "barbaric" and "a new, downward standard of humanity."

Medical and legal experts told ABC News that despite Alabama officials arguing that nitrogen gas is not cruel, there is no evidence to show that is the case.

"It's very difficult to kill people humanely, and that's what the long history of the death penalty has shown [with] these changes in execution methods," Kirchmeier said. "Every one is hailed as a new method that will be more humane than the previous one, but here we are, after more than 200 years since the country was formed, states are still experimenting with new ways to execute people."