As jury selection in the trial of accused Pittsburgh synagogue shooter Robert Bowers goes into a third week, the death penalty has been at the center in the questioning of every potential juror. After two long weeks, prosecutors and defense attorneys  are slowly but surely getting closer to seating a full jury. The trial is set to begin in mid- to late-May.

“What we do in a capital jury… is put people in the position where they have to reverse the lifelong conditioning and commitment we all make to the sanctity of human life,” said Craig Haney, a professor at the University of California, Santa Cruz who has spent decades studying death penalty cases and juries.

“[Jurors] are being asked to be part of a process where the end point might be to take a human life,” he said.

Whereas the question might be relatively easy to answer at a cocktail party or informal hypothetical discussion, these potential jurors have to consider the very real possibility that they could be someone who literally will be required to sign someone’s death warrant. When the question goes from hypothetical to being very real, even some jurors who might seem staunch on having such a responsibility on paper waver when asked more probing questions by the judge and attorneys.

The 26-page questionnaire the potential jurors filled out when they were initially called to serve in March posed almost 100 questions. Question No. 73 asked them to rank how they felt about the death penalty on a scale of 1 to 10, from strongly opposed to strongly in favor.

For example, early on in the process, lawyers questioned a Mercer County corrections officer who ranked himself as a “nine” on the questionnaire. He recalled initially seeing the shooting as “a definite death penalty case.”

But when pressed about putting his name to a death sentence, he wasn’t as eager.

“This person is still a human being,” he said. “If I’m the person who has to make that decision on whether that person lives or I want them to be put to death? That’s tough.”

Mr. Haney said even the staunchest death penalty supporters give pause when rhetoric becomes reality.

“That’s when it moves from being an attitude or a political position that people are proud to align with to personal participation in the process,” he said. “The prospect of actually deciding that someone deserves to die and should die and you’re going to be one of the people to participate in that process — it’s a whole different level of moral gravity.” He added, “any thoughtful juror would find that daunting.”

Bruce Antkowiak, a former prosecutor and defense lawyer who now serves as a professor at St.Vincent College outside of Pittsburgh agreed. He said, “It’s one thing for a person to sit in the privacy of their home or sit around a bar having a drink with their friends saying, this ought to happen, that ought to happen.”

Support for the death penalty has long been declining over the years. About 60% of U.S. adults are in favor of the death penalty, according to a Gallup poll, down from about 80% in the 1990s.

“There’s a real grappling amongst some members of the public about whether having the death penalty, even in the most heinous cases, is appropriate,” said Haney. “When I first started doing this work, people had a pat response: ‘No problem, I can do it.’ Now they’re much more reflective about it. They see the cons as well as the pros.”

Mr. Bowers, 50, faces 63 federal charges in the Oct. 27, 2018, mass shooting in Pittsburgh at the Squirrel Hill synagogue where three congregations worshiped: Tree of Life, Dor Hadash and New Light. It was the worst antisemitic attack in American history, with 11 worshipers killed across the three congregations: Richard Gottfried, Joyce Fienberg, Rose Malinger, Jerry Rabinowitz, Cecil and David Rosenthal, Bernice and Sylvan Simon, Daniel Stein, Melvin Wax and Irving Younger.