Executions in the United States fell to the lowest number in decades in 2015, and recent Popes may have helped spur the drop in public support for capital punishment.

"I think that there is continued erosion of support for the death penalty, and that's manifested across the board," explained Robert Dunham, executive director of the Death Penalty Information Center in Washington, D.C., in an interview with CNA. The center gathers and tracks information on the death penalty in the United States.

"So you see it in fewer executions, fewer capital prosecutions, fewer jury verdicts of death, and then states that are seeking death are doing so in questionable ways," he added, noting that it is the "continuation of a long-term pattern."

The number of executions in the U.S. fell to 28 in 2015, continuing its overall decline since the peak of 98 in 1999. It is the lowest number in 24 years, according to the Death Penalty Information Center.

The number of death sentences also fell from 73 in 2014 to 49 in 2015, the lowest number since the 1970s when states began re-enacting death penalty statutes.

Only six states actually conducted executions in 2015. Four states have accounted for 90 percent of the executions in past two years – Texas, Missouri, Georgia, and Florida. They were clearly "outlier states," Dunham said, "out of step with what the rest of the country is doing."

Public approval of the death penalty for convicted murderers has fallen along with the number of executions and death sentences. It peaked in 1996, according to the Pew Research Center, when 78 percent of Americans supported the death penalty for someone convicted of murder. That number has fallen to 56 percent in 2015.

And among Catholics the death penalty has similarly lost support. 53 percent of Catholics support its use now for convicted murderers, down from 59 percent in 2011. A 2004 Gallup poll showed its approval among Catholics at 66 percent.

However, the polls may not distinguish between faithful Mass-going Catholics and Catholics who do not practice their faith, Joshua Mercer, co-founder of CatholicVote.org, said. He suggested that the support for the death penalty may be significantly lower among practicing Catholics who take seriously the teaching of the Magisterium and recent papal statements against the use of capital punishment.

"Amongst Catholic voters, I think since Pope John Paul II spoke about the death penalty, we've seen the support for death penalty in the United States amongst faithful Catholics decline," Mercer told CNA.

Controversies haunted several 2015 executions and the public has taken notice, Dunham added.

More than two-thirds of the executions involved convicts "who exhibited symptoms of severe mental illness, intellectual disability, or the effects of trauma or some combination of those," he said.

For instance, Georgia executed Andrew Brannan in January for killing a sheriff's deputy 17 years ago. Brannan was a decorated Vietnam War veteran whom the Department of Veterans Affairs considered 100 percent disabled because of posttraumatic stress disorder.

Also, some states resorted to illegal or questionable means of execution because they were unable to procure the normal drugs for lethal injection. Many pharmaceutical companies have stopped providing drugs for executions, and the European Union, which strongly opposes the death penalty, has banned the export of drugs for capital punishment.

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Nebraska, Arizona, and Texas tried to import drugs for execution that were not approved by the Food and Drug Administration. The drugs were seized, and in one case Federal Express refused to transport them to Nebraska.

Some states then approved other means of execution – Utah brought back the firing squad and Oklahoma approved the use of nitrogen gas as a back-up method. Oklahoma saw a botched execution in January, and an autopsy later revealed that the wrong lethal drug had been administered.  

All this undermined confidence in the states' authority to execute criminals, Dunham said. "The level of incompetence that was involved in that administratively botched execution was astounding," he said of the January execution of Charles Warner in Oklahoma. "Can you trust the states to carry this out in a fair, humane, and competent way?"

Dunham noted that while there are multiple factors behind the drop in support, the shift in moral sensibilities cannot be overlooked, along with the influence of the papacy.

Pope Francis made a "very strong statement against the death penalty in a very public setting," he said of the Pope's Sept. 24 address to a joint meeting of Congress, in which he called for a "global abolition of the death penalty" and offered "encouragement to all those who are convinced that a just and necessary punishment must never exclude the dimension of hope and the goal of rehabilitation."

Francis talked in a "graceful and humane way" that "appealed to our better nature," Dunham added.

The drop in public support "is not something new," explained Monsignor Stuart Swetland, president of Donnelly College in Kansas, saying that recent Popes have led the way in calling for its abolition. He cited St. John Paul II's homily in St. Louis in 1999, in which he urged Catholics to be "unconditionally pro-life" and called for an end to the death penalty.

"A sign of hope is the increasing recognition that the dignity of human life must never be taken away, even in the case of someone who has done great evil. Modern society has the means of protecting itself, without definitively denying criminals the chance to reform," St. John Paul II said.

And in 2011, Benedict XVI expressed his hope for further abolition of capital punishment in countries worldwide.

Monsignor Swetland believes that these recent papal statements represent a development in the Church's teaching on the state's legitimate use of capital punishment.  

"My theological opinion, as someone who teaches moral theology and social ethics in particular, is that we're undergoing a development of doctrine here," he told CNA.

When the Church's teaching has developed over time on issues such as the morality of slavery and torture, "we go from the more permissive to the less permissive," he said, "meaning that we come to recognize that the demands of charity and mercy and justice are more demanding than we thought before."

"And so while for a while Catholic teaching permitted slavery under some specific, restricted conditions, it came to see through faith and time – same thing with torture – through faith and time that it was always and everywhere wrong."

Monsignor Swetland believes a similar shift is happening in the Church's teaching on the use of the death penalty. But he clarified that it fundamentally differs from other uses of force, such as just war or the defense of innocent life.

"The state and the actors for the state have to intend death as the end in death penalty," he said, but in the case of a just war or a policemen defending innocents, the actor intends to "stop the assailant from doing harm" and death is accepted as a "side consequence" and a "last resort."

Once the threat to innocent life is neutralized, they do what they can to preserve the life of the assailant.

"We have to stand strongly and say death is never a solution to our problems," he continued. "Modern society is tempted to say death is a solution to our problems … but what the Church is coming to recognize is that we have to be consistent and say death is never a solution. To intend death is always wrong."