JOHN YANG: Later this week unless the courts intervene, a death row inmate in Alabama is set to become the first person in the United States put to death using an untested method called nitrogen hypoxia.

Itús also called nitrogen suffocation, or nitrogen asphyxiation.

In 1996, Kenneth Eugene Smith was convicted and sentenced to death in a murder for hire plot.

Alabama tried to execute him in 2022, using lethal injection, but it failed when the execution team couldnút find a vein after trying for nearly two hours.

That attempt he told NPR haunts him as a new execution date approaches.

KENNETH EUGENE SMITH, Death Row Inmate: Iúm still carrying the trauma from the last time.

Iúm being treated for PTSD and struggle daily.

Everybody is telling me that Iúm going to suffer.

Well, Iúm absolutely terrified.

JOHN YANG: Only three states authorized nitrogen hypoxia as an alternate execution method, Alabama, Mississippi and Oklahoma.

Last week, the Alabama Solicitor General called it the most painless and humane method of execution known demand.

The U.N. Human Rights Office says it could amount to torture.

Robin Maher is executive director of the Death Penalty Information Center.

Robin, first of all, what is this method?

And what do we know about how Alabama plans to implement it?

ROBIN MAHER.

Executive Director, Death Penalty Information Center: Well, what we know about it is what Alabama has chosen to share with us in a highly redacted protocol, which conceals certain critical details and also raises more questions about its safety and its effectiveness.

The broad outlines are that Mr. Smith will be fitted with a mask, a face mask and be forced to breathe pure nitrogen gas.

At that point, his organs will begin to fail and ultimately death will result.

Thatús the theory.

But itús only a theory because this has never been used before in an execution in the United States, nor anywhere in the world as far as we know.

JOHN YANG: What could go wrong?

What are the worries about what could go wrong?

Well, ROBIN HAMER: Well, Mr. Smithús lawyers have argued a few certain things.

One is that theyúre worried about the face mask itself the way that it fits on his face, if it becomes dislodged for any reason, for example, if Mr. Smith begins to panic, or if itús dislodged when heús praying audibly, or making a final statement, then that could affect the flow of the gas and prolong his execution.

The other question is the safety of others in the room.

Weúre worried about people like the religious adviser who will be with him, heús been forced to sign an acknowledgement that he understands the dangers heúll be in with this use of odorless and colorless gas.

And Mr. Smithús lawyers also argue that he may vomit in the mask and aspirate, which would also prolong his suffering, and his death.

JOHN YANG: Why are students looking for alternate methods of execution?

ROBIN MAHER: Well, that story really begins several years ago, and when pharmaceutical companies discovered that their drugs were being used in executions, they responded by withdrawing some of these drugs, or refusing to sell them to prisons.

And that led states to do a variety of things, some began compounding their own drugs, some began experimenting with different combinations of drugs that had never been tested before.

And what we saw then was a series of botched executions, really gruesome spectacles of people that were obviously in a lot of pain and distress during their execution.

So, now states have turned to identifying alternate methods, some of them have gone back to old methods like electrocution, and firing squad and Alabama will be the first to use nitrogen gas.

JOHN YANG: How states approach using a new technique?

I mean, obviously, as you pointed out, lethal injection was new at one point what how do they approach this?

ROBIN MAHER: Well, you know, part of the problem here is that we donút have all of the details and transparency and accountability.

Those are principles of good governance everywhere.

What we donút have from Alabama is a clear understanding of what it knows and how this procedure will go forward.

And I think thatús whatús prompting a lot of concerns.

JOHN YANG: Only five states carried out capital punishment last year.

And there were many states that have the death penalty, but just have not carried it out.

What does this tell us if anything about the Americans attitudes and approach toward capital punishment?

ROBIN MAHER: Well, I think it tells us a lot.

I mean, first of all, as you say, very few states are still using the death penalty.

Very few states are still imposing new death sentences, the majority of the country has really turned away from using the death penalty.

And there was an important new poll public opinion poll that came out, in which it said for the first time, Americans, more Americans believed the death penalty is administered unfairly, then fairly, theyúve lost trust, theyúve lost confidence that the death penalty can be used in a fair and accurate manner.

And that, that I think spells a real change for the death penalty in the United States going forward.

JOHN YANG: I mean, aside from the method the Alabama wants to use in this execution, is the question that they have already tried to execute and failed.

Can a second attempt be made?

Is this ever happened before?

ROBIN MAHER: This is extraordinarily rare.

It happened quite recently, again in Alabama just a few years ago, but it is extraordinarily rare for someone to survive an execution attempt.

And as you heard from the clip, you know, Mr. Smith is still suffering the effects from that botched execution attempt.

The U.N. certainly has said it has concerns that this is a kind of torture.

And so the Supreme Court is being asked to look at that, that very question in its upcoming case.

JOHN YANG: Robin Mahara, the Death Penalty Information Center Thank you very much.

ROBIN MAHER: A pleasure.