AMNA NAWAZ: Moments ago, a South Carolina man was put to death by a firing squad after being convicted in a 2001 double homicide to which he pled guilty.

The execution of 67-year-old Brad Sigmon marks the first time since 2010 that a firing squad has been used in this country.

And it comes as the Trump administration works to expand capital punishment, calling for the restoration of federal executions.

For more on all of this, I'm joined by Robin Maher, executive director of the nonpartisan Death Penalty Information Center.

Robin, welcome back to the program.

Thanks for joining us.

ROBIN MAHER, Executive Director, Death Penalty Information Center: It's a pleasure.

AMNA NAWAZ: So I should share that we have just got a release of Brad Sigmon's final words, his last statement.

I want to read just a part to you now.

He quoted several Bible passages.

And he also said: "I want my closing statement to be one of love and a calling to my fellow Christians to help us to end the death penalty."

Robin, it's worth reminding people he chose this method, firing squad, in South Carolina.

And this is part of what his lawyer, Bo King,told us about why he chose this method.

BO KING, Attorney For Brad Sigmon: We know there is something wrong with how South Carolina is carrying out lethal injections, and Mr. Sigmon has repeatedly asked for the information that you would want to know why.

But he's been denied that at every turn.

So, even though the firing squad hasn't been used ever in South Carolina and hasn't been used in the United States in 15 years, he chose that.

It was the best choice that he could make, given all the information that's being kept from him.

AMNA NAWAZ: Robin, what do we know about how executions have been carried out in South Carolina?

ROBIN MAHER: Well, South Carolina carried out its last two executions using lethal injection.

The problem is that the autopsies of the men who were executed revealed that they received more than double a dose of the one drug protocol that was used, that's pentobarbital, for unknown and unexplained reasons.

And the autopsies also showed that one of these men had blood and fluid in his lungs, which indicated that he experienced painful symptoms akin to drowning, a condition called pulmonary edema.

So all of this prompted some very reasonable questions from Mr. Sigmon's lawyers about what drug South Carolina intended to use and how could they explain these anomalies?

As Mr. King just said, they never received that information.

And so Mr. Sigmon was forced to make a very difficult choice, to choose from -- to choose a method he knew almost nothing about, and chose instead to use the firing squad, which had the most information available.

AMNA NAWAZ: And this... ROBIN MAHER: His third option, of course, was to be executed in a 110-year-old electric chair.

That was the default method in South Carolina.

AMNA NAWAZ: And, just for context, this method, a firing squad, how common is this nationally?

Where is it even allowed.

ROBIN MAHER: It's not allowed in very many places.

Only three executions have taken place in the modern death penalty era, and they have all been in Utah.

Five states now authorize use of the firing squad, mostly as alternative methods.

Idaho is considering making it its primary method.

AMNA NAWAZ: The couple that Mr. Sigmon killed were named Gladys and David Larke, his ex-girlfriend's parents.

And we should note even their adult children who testified at the trial were very split on what kind of penalty they wanted to see here.

When you look, Robin, at where the American people are on this issue right now, according to Gallup, support for the death penalty for people convicted of murder, that's been falling over the years, but there are still more people today, some 53 percent, who are in favor of it, than who are not.

That's 43 percent.

What does that say to you?

ROBIN MAHER: Well, there's a diversity of opinions about the death penalty, even among, as you say, family members of people who've lost loved ones to violence.

And that's a big change from what we were previously told years ago.

Many family members now say that the death penalty does not bring them any peace or closure.

But, as you say, public support is at a 53 percent, which is a five-decade low.

When you dig into those numbers, you see some very interesting facts, including that younger generations, people age 18 to 43, the majority of those younger people now oppose the death penalty.

And even among people who support the death penalty, that 53 percent, I think there's growing discomfort with the execution of people with severe mental impairments or who are suffering from brain damage and the long-term effects of trauma and violence, like Mr. Sigmon.

AMNA NAWAZ: We saw, within days of him taking office, President Trump directed the U.S. attorney general to pursue the death penalty for, as he put it, all crimes of a severity demanding its use.

He's also encouraged more use of capital punishment at the state level.

Is that directive, that guidance, is that having an impact, and could it down the line?

ROBIN MAHER: Well, I think President Trump has made no secret of his enthusiasm for the death penalty, but his influence in the states is going to be pretty limited.

Decisions will still be made by local juries, who have been increasingly reluctant to sentence people to death over the past few years, and also by local elected officials who may schedule executions for their own reasons.

But I don't think even President Trump's enthusiasm will reverse the decades of long-term trends that show a dramatic reduction in support for and use of the death penalty.

AMNA NAWAZ: Robin Maher, executive director of the nonpartisan Death Penalty Information Center, thank you for joining us tonight.

ROBIN MAHER: Thank you.