AUSTIN, Texas (AP) — A Texas man set to die this month is at the center of another push for clemency in the U.S., this time backed by several GOP lawmakers and bestselling author John Grisham, who say a father’s 2002 conviction for killing his infant daughter deserves a second look.

Their pleas to spare Robert Roberson, who is set to die by lethal injection on Oct. 17, comes after Missouri and Oklahoma carried out executions last month over calls to grant two condemned men lesser punishments, underlining how rare clemency remains for death row prisoners.

The cases highlight one of a governor’s most extraordinary powers — whether to allow an execution to proceed. In Texas, the state’s parole board and Republican Gov. Greg Abbott have yet to weigh in on Roberson, whose defenders say was convicted based on faulty scientific evidence.

In Missouri, the execution of Marcellus Williams on Sept. 24 reignited calls for transparency in the decision-making process after a prosecutor and the victim’s family had urged Republican Gov. Mike Parson to reduce the sentence. Parson said multiple courts had not found merit in Williams’ innocence claims.

“Capital punishment cases are some of the hardest issues we have to address in the Governor’s Office, but when it comes down to it, I follow the law and trust the integrity of our judicial system,” Parson said in a statement before Williams’ execution.

Clemency is the process that allows a governor, president or independent board to lessen the sentence of a person convicted of a crime. In most states, a state board recommends clemency to the governor before it can be approved.

Clemencies are usually a last push by defendants on death row to have their sentence reduced after all other efforts in the judicial system have failed.

Historically, grants for clemency are rare. Aside from a few mass orders from governors to commute all death sentences in their state, less than two have been granted on average per year since then, according to the Death Penalty Information Center.

Oklahoma Gov. Kevin Stitt rejected a recommendation from the state’s parole board to spare the life of Emmanuel Littlejohn life before he was executed. In a 3-2 vote, the board appeared convinced by Littlejohn’s attorneys, who questioned if he or a co-defendant were responsible for a 1992 killing of a store owner.

Stitt — who has granted clemency just once out of the five times the board has recommended it during his nearly six years in office — said in a statement that he did not want to overturn a jury’s decision to execute Littlejohn “as a law and order governor.”

In Missouri, Williams’ execution followed public outcry from the victim’s family and prosecutor last month in a historic week of five executions in a seven-day span.

It’s unclear if Missouri’s Parole Board, which makes confidential recommendations to the governor on clemency requests, advocated for Williams’ execution. Williams’ defense attorneys said those records should be public.

“Transparency is a hallmark of Democracy, and it is woefully missing here,” they said in a statement.

Governors are usually balancing a few things when deciding to commute a sentence, including the severity of a crime or if they’re remorseful, according to Arizona State University law professor Dale Baich, an attorney who has represented people facing execution.

But Baich also suspects other factors can come into play. “I think it all comes down to politics,” Baich said.

Eighty-six state representatives — as well as medical experts, death penalty attorneys, a former detective on the case and Grisham — are supporting Roberson because they believe his conviction was based on faulty scientific evidence.

Roberson was sentenced to death for killing his 2-year-old daughter, Nikki Curtis, in 2002. Prosecutors claimed he violently shook her to death from what’s known as shaken baby syndrome. In a letter sent to the board last month, medical professionals claimed that Curtis’ injuries aligned with pneumonia and not shaken baby syndrome.

Prosecutors have claimed that the science of shaken baby syndrome has not changed significantly since Roberson’s conviction and that the evidence against him still holds.

“We want our justice system to work. And I think Texans deserve to know that if a man is going to be executed, that it is right and he is guilty,” state Rep. Lacey Hull, a Republican from Houston who is one of 30 GOP state representatives to support clemency for Roberson, said last week after she and other lawmakers visited Roberson in prison. “And if there’s even a shadow of a doubt that he is innocent, we should not be executing him.”

Some Republicans view Roberson’s case as a parental rights issue about the safeguards that need to be put in place to prevent parents from being falsely accused of child abuse.

Abbott can only grant clemency after receiving a recommendation from the the Texas Board of Pardons and Parole. He has commuted a death sentence only once in nearly a decade as governor.

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Ballentine reported from Jefferson City, Missouri. Associated Press writer Juan A. Lozano in Houston contributed to this report.

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Lathan is a corps member for the Associated Press/Report for America Statehouse News Initiative. Report for America is a nonprofit national service program that places journalists in local newsrooms to report on undercovered issues.