(CNN) -- Billy Ray White vowed 20 years ago that when he got out of prison, he would track down the relatives of the man he'd murdered and subject them to gruesome deaths.

In a handwritten letter to J.D. Hall's daughter, the convicted killer promised to carve her up like a turkey and make her head into a flower pot. In another letter to Hall's son, he said he would put him through a meat grinder and force his relatives to eat him.

"You can run but you can't hide. You can go to the police, but they can't protect you. You can change your name, address, or even move, but I will always find you," he wrote in a letter postmarked May 15, 1989, to Hall's widow. "They can't keep me in here for the rest of my life."

The letters were from "Charles Manson," but White has admitted to writing them. In a 1991 letter to the Georgia State Board of Pardons and Parole, he acknowledged that writing them was a "stupid thing" to do and asked for forgiveness.

But the letters continue to haunt him, just as they do the recipients.

In late June, White was denied parole for the sixth time since he was sentenced in 1985 to two consecutive life sentences plus 10 years for Hall's murder, armed robbery and theft of a motor vehicle, a parole board spokesman said.

Prosecutors and the Hall family received the news from the parole board last month after mounting an impassioned campaign to keep White behind bars, citing fears that he would make good on his threats.

"If White were ever to be released, I would be terrified to step foot out of my house," one relative wrote in a letter to the parole board. "I also believe with every fiber of my being that our community would also be placed in serious danger."

The family declined to talk to CNN.

The parole board said in a June 24 notice to White that his release "would not be compatible with the welfare of society" because of the severe nature of his crimes.

But the debate is not over. His parole comes up again for reconsideration next April, in a scenario that plays out similarly every day across the country, pitting the interests of surviving victims against the rights of convicts to re-enter society if deemed ready.

White was sentenced to two life sentences before the era of life without parole. Had he been sentenced today, he would be a likely candidate for life without parole, said University of Georgia law professor Ronald Carlson.

"This is a classic case of how parole boards have to balance a commendable life after the crime versus the heinousness of the offense, but that's somewhat of a diminishing problem because we have now life without parole for this sort of crime," Carlson said. "In the interim, there's going to be some dramatic cases where prisoners who've done some pretty awful things are going to try to get parole."

The burden is on the prisoner to convince the board that he is not a future danger to society and that his efforts to rehabilitate himself outweigh the heinousness of his crime.

"One of the things that's key to the decision-making process is, frankly, an educated guess," Carlson said. "The board is informed, but there's still no scientific judgment available about future dangerousness of an applicant."

In that regard, the letters are especially damning, Carlson said.

"The board will have to decide if he's playing a waiting game or not," he said.

Unlike many convicts seeking parole, according to Carlson, White has someone in his corner. His sister Judy says he is a different person from the "troubled teen" who shot Hall at his home in Douglasville, Georgia.

The woman, who asked that her last name not be used out of fear of reprisal, said people might understand her brother better if they knew of the neglect and abuse he endured as the child of alcoholic parents.

"They're reviewing him on those stupid letters -- which he completely regrets -- but he was a young teenager when all this happened. He's 39 now," his sister said in a phone interview from her Florida home. "He just wants a chance to prove to the world that he's changed."

White has spent most of his life in state custody. He was 13 when he shot Hall in the face on the morning of March 30, 1985.

He had arrived in Georgia from Florida three days earlier with a case worker for an interview at a juvenile psychiatric facility. He was being considered for treatment of "antisocial attitudes" and "underlying rage issues." The pair was driving back to the airport when he escaped from the car, according to court records.

Over the next few days, White broke into vehicles and buildings in the Douglasville area, obtaining a .44 caliber handgun. He was stealing Hall's pick-up truck from his driveway when he shot the 53-year-old.

White never denied shooting Hall, a well-known member of the community who ran a family-owned grocery store and a construction company.

Because of his age, White was not eligible for the death penalty. Georgia law at the time did not have life without parole, so he was sentenced to two consecutive life terms plus 10 years. The question of whether he would be released has always been a matter for the Georgia Parole Board.

White was four years into his sentence when he sent letters to Hall's widow and three children.

"I might be 39 or 40 when I get out but I'll still be in prime shape," he said in the letter to Hall's widow, who, according to her family, has never read it.

He did not face charges for the letters, according to prosecutors in Douglas County, and has not contacted the family since.

But the letters have had a lasting impact.

"I remember my parents not even wanting us to play outside without them for many months after receiving the letters. It took several years to put all this behind us and feel safe again," one relative wrote the parole board, explaining that the letter was unsigned out of fear that White would use it to locate the family. "I would never feel safe again if he were released."

Douglas County District Attorney David McDade, who prosecuted White in 1985, has led the fight to keep him in prison, citing the nature of his crime, his failure to show remorse and, not surprisingly, the letters.

"I've never seen another case where the defendant, after going to prison, set about to terrorize and torture the victim's family," McDade said. "He didn't do it as a knee-jerk reaction to his sentence; he had four years to think about it."

But White's sister said he has already proven that he does not intend to harm the family. From July 2006 to March 2007, White left prison for a work release program, according to the Georgia Department of Corrections.

In a letter to White dated February 14, 2006, the board said it would recommend his transfer to a halfway house in downtown Atlanta, and tentatively grant him parole upon successful completion of the program.

While at the center, White rode the city bus almost daily to work and "kept his nose clean," according to his sister.

The Georgia Department of Corrections corroborated her claims. "There is no documentation of infractions (DR's) during his stay at the Atlanta Transitional Center," a spokeswoman said in an e-mail.

Nor did he contact the Hall family.

"He had money; he had opportunities to get on a bus and leave the state or to try something, but he never did," his sister said. "He was looking forward to a really great future."

In March 2007, however, White was sent back to a more secure prison.

"The Parole Board can decide at anytime to reconsider a decision and it is my understanding they did so," spokesman Steve Hayes said in an e-mail.

"The Parole Board's decisions are based on everything available to them including the offender's case file," he said, adding that the file is confidential.

In a letter to the parole board after its decision, dated February 27, 2006, prosecutor McDade implored the panel to never consider White's release.

"I cannot envision any set of circumstances that could ever justify any Board EVER releasing Mr. White under any conditions. You will never be able to justify releasing him considering what he did and what he said to the victims afterward," the prosecutor wrote.

In 1991, White offered an explanation for why he wrote to Hall's family.

He told the parole board he was "scared of the Hall family and I wanted them to be scared of me. I never intended to act out my threats. I am scared that one day when I do get out that someone will try and kill me for what I did."

In the 1991 letter and another in 2006, White also claimed that he accidentally shot Hall as the man approached the vehicle. White said he intended to fire a round into the air to scare him away. Instead, he shot Hall in the face.

"I had no right to be on his property or to take anything he or anyone owned. I was wrong. But premeditated murder means you had a forethought. I didn't have any thought of shooting, harming or killing that man," he wrote.

Since he's been in prison, White has earned his GED and learned software programming from instructional books.

His sister says he's come a long way from his tumultuous upbringing in Hernando, Florida, where he and his two siblings were picked on at school for being "poor kids" and were emotionally and physically abused at home. Punishment for minor offenses ranged from severe beatings from their father, she said, to death threats and nights locked in sheds.

By the time their mother took the children away, when White was 7, he'd become withdrawn and quiet and began running away from home, she said.

"It's hard to understand what our childhood was like if you weren't there," his sister said. "But Billy never really had a chance. He's been raised in prisons."

She said she is ready to take him into her home, pay for his college education and offer him a job with the family's software programming company if he is released.

"We hurt for this family, and we wish for God to bless them every day, but I'm a firm believer that we have to let the hurt die and go on so both our families can prosper," she said.

The safety net that his family offers, plus his efforts to acquire marketable skills, could weigh in his favor, according to law professor Carlson.

"I think it's noteworthy that the family is there to provide financial and emotional support for him. That's rare," Carlson said. "Very few prisoners have a good job sitting there, waiting for them ready in areas of their strengths."

But McDade, the prosecutor, believes White already forfeited his chance at freedom.

"He deserves the same leniency that he gave his victim," McDade said. "I have no leniency in my heart for Billy White."