The murders were so brazen, so brutal, they stunned the people of Missouri.

Just after midnight on June 22, 2000, Michael Tisius and Tracie Bulington entered a county jail, intent on forcibly freeing an imprisoned friend. Mr. Tisius, 19 years old and carrying a gun, shot and killed two guards during the attempt, then fled.

When a jury was asked to sentence Mr. Tisius for his crimes, its members spent several hours deliberating in July 2010 before rendering a decision: the death penalty.

Now, with Mr. Tisius’ execution set for Tuesday, that jury is facing scrutiny that could cast doubt on the proceedings.

In an unusual step, six jurors, including two alternates, have said in sworn affidavits included in a clemency petition that they would be supportive or would not object if the governor of Missouri stepped in to commute the sentence to life imprisonment, rather than death. It is rare, experts said, to see so many jurors formally taking such a stand in a death penalty case.

Another juror, when contacted recently by legal representatives for Mr. Tisius, told them that he could not read in English, a requirement in Missouri courts for jury service. A federal judge ordered last week that the execution be halted while the claim of illiteracy was investigated, but on Friday, an appeals court overruled that decision.

In a 56-page petition sent to Gov. Mike Parson of Missouri, jurors recounted in statements obtained from Mr. Tisius’ defense team why they have changed their thinking since the sentencing 13 years ago.

They were still convinced of his guilt, the jurors said, and believed he should never be released from prison. But they spoke of new details they learned from Mr. Tisius’ legal team and what they remembered from the trial: the harrowing background of Mr. Tisius’ childhood, which included abuse and neglect; of his mental impairments; and of his good behavior in prison since his conviction.

“I believe that people can change and should get second chances,” one juror said in an affidavit.

“At this time, based on what I have learned since the trial, I would not object if Mr. Tisius’ sentence were reduced to life without parole,” another juror said.

There is no legal recourse for jurors who have had a change of heart about a death sentence, said Juandalynn Taylor, a visiting professor at Gonzaga University School of Law who teaches on the death penalty, though lawyers often find examples of it in interviews with jurors during the appeals process.

“Jurors change their minds all the time,” she said. “But if no one goes and asks them and discovers it, then we don’t find out about it in public.”

In interviews with The New York Times, two jurors said they have been haunted by their experience. One woman who served as an alternate said she has suffered from anxiety, sleeplessness and guilt. If she had been allowed to vote, she said, she would not have chosen the death sentence.

Another juror, Jason Smith of Republic, Mo., said that in the 13 years since the sentencing, his views on Mr. Tisius, who is now 42, have shifted.

During deliberations, Mr. Smith said, he felt it was a crucial fact that Mr. Tisius had killed more than one person. Mr. Tisius had an opportunity to stop before shooting the second jail employee, Mr. Smith recalls reasoning, making the death penalty a just punishment.

But now he said he knows, based on what he was recently told by Mr. Tisius’ legal team, that doctors who have examined him concluded that he had mental deficiencies that could have impaired his decision-making. And Mr. Smith has learned about medical research showing that the frontal lobe of the brain is not fully developed in the teenage years.

Mr. Smith, 49, said he still supports the death penalty in certain cases and feels that Mr. Tisius should spend the rest of his life in prison.

But he no longer believes Mr. Tisius deserves to die.

“I feel angry and remorseful,” he said. “I feel that I wronged Michael.”

Public support for the death penalty in the United States has waned for decades, and Missouri is one of only four states to have carried out an execution in 2023, along with Florida, Oklahoma and Texas, according to the Death Penalty Information Center.

This year, Missouri executed Amber McLaughlin, a transgender woman who had been found guilty of murdering her ex-girlfriend, and Leonard Taylor, convicted in 2008 of a quadruple murder. Two more executions, including Mr. Tisius’, are scheduled in Missouri this year.

When a jury in 2010 was asked to determine Mr. Tisius’ sentence, they were told of the botched escape attempt that resulted in the murders of Jason Acton and Leon Egley: Mr. Tisius had been trying to free an inmate, Roy Vance, who had previously been his cellmate. Mr. Vance, who is serving a life sentence in prison for his role in the murders, has since said that he manipulated Mr. Tisius to carry out the escape plan.

The other person who was trying to free Mr. Vance was Mr. Vance’s girlfriend, Tracie Bulington. She was sentenced to two consecutive life sentences for her role in the killings.

During the resentencing hearing in 2010 — convened after the court found evidence of prosecutorial misconduct in a first hearing — jurors were told of Mr. Tisius’ difficult life, including abuse at the hands of his older brother. One juror, Ginny Young, told The Columbia Daily Tribune in 2010 that as soon as the group left the courtroom, several jurors began to cry.

“They felt bad that they had to put this man to death,” Ms. Young said at the time. “One of them said, ‘You wouldn’t be human unless you feel bad.’ I guess I am not human, because I don’t feel bad. Maybe I need therapy. I think the punishment is justified by the crime.”

Some jurors who were contacted by Mr. Tisius’ legal team affirmed their original decision that Mr. Tisius should be sentenced to death, or declined to sign affidavits, said Keith O’Connor, a lawyer for Mr. Tisius.

An alternate juror interviewed by The Times recalled riding in a van with other jurors after leaving the courthouse. The juror, who declined to be named because she said she had concerns about privacy, remembered weeping, thinking that the jury had made a mistake.

Mr. Smith said it was quiet during much of the long ride.

“A lot of people were probably just reflecting on it,” he said. “We were all ready to get home.”

After the sentencing, he went back to the rhythms of his life. He talked about the case with his parents. At least once, he looked up Mr. Tisius’ booking photo on the Missouri Department of Corrections website.

In the dining room of his home, Mr. Smith picked up the affidavit that he signed supporting the commutation of Mr. Tisius’ sentence, a document that has been laid out on the table since last year. With the execution date nearing, Mr. Smith has been thinking about Mr. Tisius and the trial often, he said.

“I wasn’t emotionally torn up with my decision,” said Mr. Smith, who works in food distribution. But it still weighed on him.

“I hated having a part in somebody dying,” he said.

For Linda Arena of Rocheport, Mo., the sister of Jason Acton, one of the slain jail employees, the death sentence brought relief. The years since have been a long wait for what she sees as justice.

Ms. Arena, 73, remembers her brother as a boy, affectionate and funny, with a deep love of the outdoors. As an adult, she said, he took a job at the jail because he hoped it would be a steppingstone to a position as a park ranger.

It is difficult for Ms. Arena to even say Mr. Tisius’ name.

“He’s a nonentity to me,” she said. “A nonentity who took my brother.”

The Missouri Supreme Court denied an appeal from Mr. Tisius and, in March, scheduled his execution.

Since then, opponents of the death penalty have intensified their efforts to persuade Mr. Parson, the Republican governor, to commute the sentence.

Archbishop Christophe Pierre, the Pope’s representative to the United States, appealed to Mr. Parson for clemency. The American Bar Association argued in a letter that capital punishment should be prohibited in cases of people who have committed crimes while 21 years old or younger.

Mary Fox, director of the Missouri State Public Defender system, asked Mr. Parson to commute the sentence, saying that Mr. Tisius was not effectively represented during the tria. (Christopher Slusher, a lawyer who defended Mr. Tisius during the sentencing in 2010, did not respond to a message.)

Ms. Fox said that the process of capital punishment can be troubling for jurors, prison employees who get to know inmates and the lawyers who defend their clients.

“One of my jobs is to take care of the people who work for me, and one of the things that I see is the trauma that my folks are suffering,” she said. “It’s traumatic for everyone involved.”

In the final days before Mr. Tisius’ scheduled execution, the clemency petition — and statements from several jurors in support of a commutation of his sentence — has left Ms. Arena confused and angry.

“It kind of makes me mad, because they listened to all the evidence,” she said. “They knew that this guy planned to do that. They brought a gun on purpose. He killed Jason and he killed Leon.”

All the years that her brother has been gone, Ms. Arena has thought of Mr. Tisius spending his days in prison. Why was he free to be alive, she has asked, eating meals, having conversations with other people, when Jason was not?

Ms. Arena is determined to drive on Tuesday morning to Bonne Terre, where the execution is scheduled to take place.

She plans to bring a photo of Jason and hold it close. But she is not sure how the execution will leave her feeling, or whether she will be able to look Mr. Tisius in the eye.

“It will be hard,” Ms. Arena said. “I’m not sure how it’s going to affect me, watching someone die.”

Through a spokeswoman, the Missouri attorney general declined to comment, citing pending litigation.

In a statement from prison, Mr. Tisius said he still believed there was a chance that Mr. Parson would commute his sentence. “My only hope is that the Governor makes his decision based on me, my remorse, my life, and my rehabilitation over the last 23 years,” he said. “I feel like I’ve changed, I hope he can see that in me too.”

Mr. Parson has not yet issued a statement on his decision regarding Mr. Tisius’ clemency petition.

Kirsten Noyes contributed research.