Why is Alabama executing a man using nitrogen gas?

A death row inmate is set to be executed using a novel method. Why are authorities in Alabama using nitrogen gas, and why is it controversial?

Kenneth Eugene Smith was originally scheduled to be put to death with deadly drugs in November 2022.

Prison staff inserted one intravenous line, but two lines were required to administer the lethal injection.

After they struggled for an hour to insert the second IV, the execution was called off.

Now Smith - who was convicted of the murder-for-hire of a preacher's wife in 1988 - is scheduled to be executed using nitrogen gas instead. The gas will choke off oxygen to his brain, a process called nitrogen hypoxia.

It's a controversial method that has never been used before by a US state.

And it represents the latest step in the search for a new way to execute convicted criminals - even as the death penalty has become less popular over time.

Around half of US states still have death penalty laws. Execution methods vary, but some states still allow execution by hanging, firing squad or the electric chair.

According to the Death Penalty Information Center (DPIC), a not-for-profit organisation that is critical of how executions are administered, no method has been found to violate the US Constitution's ban on "cruel and unusual punishments", although some state courts have outlawed some methods.

In recent decades, however, most states have converged on lethal injection - the administration of intravenous drugs that sedate and kill the convict - as the main execution method.

Texas was the first state to execute a convicted criminal with lethal injection, in 1982.

Last year, 24 people were executed in the US - most of those in Florida and Texas, and all by lethal injection.

The process, however, is not always straightforward. Several months prior to Smith's previous botched execution, Alabama authorities failed to put to death another death row inmate, Alan Miller, also because of difficulties inserting an IV needle. Several other lethal injection executions have also not gone according to plan.

And states have recently had difficulty in obtaining lethal injection drugs. In some cases, drug manufacturers won't sell them, or no longer produce them.

The UK and the European Union banned exports of the chemicals in 2011, and five years later American drugs giant Pfizer, the last open-market source of lethal injection drugs, announced it would no longer sell them to be used in executions.

The result is that states have been scrambling for other ways to execute prisoners.

The use of nitrogen gas in executions has been approved by three states, including Alabama in 2018, and has withstood various legal challenges since.

But critics of the procedure say that method is untested and unproven.

"It's an experimental procedure," says Dr Jeff Keller, President of the American College of Correctional Physicians. "Many things can go wrong."

Prison officials will strap a mask to Smith's face and administer the pure nitrogen gas for up to 15 minutes.

Deborah Denno, a criminologist at Fordham Law School who specialises in research into death penalty methods, says the procedure "is supposed to be painless".

"But I have to emphasise - that's in theory," she says.

"These masks don't usually don't fit people," she says. "They're not airtight, air can get in."

Smith could begin vomiting or survive the attempted execution with brain damage, she says.

Proponents of the method reject criticism and point to examples of nitrogen hypoxia occurring in industrial accidents, with victims apparently becoming unaware of what is happening to them.

One study prepared for Oklahoma lawmakers considering whether to allow nitrogen gas executions cited research that concluded "without oxygen present, inhalation of only 1­2 breaths of pure nitrogen will cause a sudden loss of consciousness".

Alabama State Attorney General Steve Marshall has called nitrogen gas "perhaps the most humane method of execution ever devised".

On Wednesday the US Supreme Court declined to hear Smith's legal challenge contending that attempting to execute him a second time violated his constitutional rights.

The flurry of attention over Smith's scheduled execution comes as enthusiasm for the death penalty has ebbed across much of the US.

The number of executions is down substantially from a peak of 98 in 1999, according to the DPIC.

Not only are fewer death sentences being carried out, in fewer states - just 10 have executed a prisoner in the last decade - but fewer death penalties are being handed out by courts.

"We've seen a big change in American support for the death penalty," says Robin Maher, the DPIC's executive director.

Polling organization Gallup, which has been tracking public attitudes towards the death penalty for nearly a century, says that 53% of Americans favour the death penalty for convicted murders.

That figure is down from a high of 80% which the survey registered 30 years ago.

Ms Maher says a variety of factors resulted in the death penalty becoming less common - not only botched executions, but nearly 200 exonerations of death row inmates, legal changes which prohibit mentally impaired people and juveniles from being put to death, and the increasing reluctance of juries to hand down death sentences.

"I expect that trend will continue," she says.

With reporting by Bernd Debusmann Jr and Anahita Sachdev