Hours before David Miller is scheduled to be executed in Tennessee's electric chair, the state's governor has rejected Miller's request that his sentence be commuted to life in prison.

Gov. Bill Haslam released a one-sentence statement Dec. 6, saying that "after careful consideration of David Earl Miller's clemency request, I am declining to intervene in this case."

Miller, 61, was convicted of the 1981 murder of Lee Standifer, whom he bludgeoned to death and stabbed. He was sentenced to death, and chose to be executed by the electric chair rather than by the state's controversial lethal injection protocol.

Attorneys for Miller filed a clemency petition with the governor last week. The petition said that Miller "accepts responsibility for the death of his friend."

The petition also argued that Miller suffers from "severe mental illness" that renders him "far outside that group of offenders who are the worst and for whom the death penalty is reserved."

Miller's attorneys said that sentencing courts had not considered "years of horrific physical abuse, sexual assault and neglect," or their ensuing effects, when the man was sentenced to death.

Court records say that as a child Miller was routinely beaten by an alcoholic stepfather, and Miller says he was serially sexually abused by family members, including his mother, beginning at age 5. His family disputes his claims.

According to The Tennessean, Miller attempted suicide at age 6, and spent most of his childhood in state institutions. After a brief stint in the Marine Corps, he became a drifter, doing manual labor and hitchhiking.

In the early 1980s, Miller lived briefly with a Baptist pastor and his family in Tennessee, and during that time he met Standifer. She was, like Miller, in her early twenties. She was mildly brain damaged, and lived at the YWCA in Knoxville. The two became friends.

On May 20, 1981, Miller killed her. He was using LSD at the time, and drinking. He claims not to know exactly what happened, though he acknowledges his responsibility for Standifer's death. He fled, and was arrested a week later, passing counterfeit bills in Ohio.

Miller's attorneys have argued that Standifer's death was the result of a psychotic fury, the result of post-traumatic stress disorder and other psychological illnesses, manifested amid an argument between the two.

He was convicted in 1982 and sentenced to death.

Tennessee's bishops say that while "there was absolutely no justification for the crime Mr. Miller committed 38 years ago," the death penalty is not necessary.

In a Dec. 5 statement, Bishops Richard Stika of Knoxville, Mark Spalding of Nashville, and Joseph Kurtz, apostolic administrator of Memphis, wrote that "the Church teaches that the death penalty is simply not necessary when society has other means to protect itself and provide a just punishment for those who break civil laws. Rather than serving as a path to justice, the death penalty contributes to the growing disrespect for human life."

"We believe that all those convicted of terrible crimes still retain their human dignity and deserve a chance to live," they added.

"To recognize the dignity of the lives of those on death row is not to deny the dignity of the lives of their victims or their grieving loved ones left behind. The lives of victims and sinners alike should be respected; the taking of another life will serve no purpose but vengeance."

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Pope Francis is an outspoken opponent of the death penalty, revising in August the Catechism of the Catholic Church to classify its use as "inadmissible."

The pope's predecessor, Pope Benedict XVI, called leaders in 2011 to "make every effort to eliminate the death penalty."

Pope St. John Paul II prayed publicly for universal abolition of the death penalty.

In the 1995 apostolic exhortation Evengelium vitae, he wrote that governments "ought not go to the extreme of executing the offender except in cases of absolute necessity: in other words, when it would not be possible otherwise to defend society. Today however, as a result of steady improvements in the organization of the penal system, such cases are very rare, if not practically non-existent."

Haslam has declined to stop two other executions in 2018.

Miller's legal team has petitioned the U.S. Supreme Court for a stay of execution. He is scheduled to be executed at 7 p.m., Dec. 6.