Those cases were among the examples provided to legislators last year by Tennesseans for Reasonable Parole Review, an informal collective including a juvenile court judge, a juvenile court administrator, researchers, people who were incarcerated as youths, and the American Civil Liberties Union of Tennessee.

“The bottom line is most of these kids who end up doing very horrific crimes or tragic crimes have all in some ways been victimized,” said Judge Sheila Calloway, the juvenile court judge, who has been pushing for reform. “When we lock them up for life, we discount their ability to rehabilitate and become better citizens.”

A previous attempt to pass legislation that would make juveniles eligible for parole after serving 30 years instead of 51 years expired in committee last year. Part of the opposition to the bill cited the murder of a family in eastern Tennessee’s Greene County in 1997 by six youths, two of whom were 14 and 17 and were tried as adults. If passed, the bill would have retroactively applied to the Greene County killers.

Dan Armstrong, the elected district attorney in the county, lobbied legislators last year when the bill for juvenile sentencing changes was being considered. He said such legislation would make a “mockery” of the judicial system, particularly in cases involving the murder of multiple people.

“I understand the focus on juvenile justice reform,” he said. “I am not necessarily opposed to the idea. But the community has lived with this for over 20 years. How come we still have to fight this battle to keep these people in jail?”

In Ms. Brown’s case, she had run away from home at 16 and lived with a pimp who raped and abused her while forcing her to become a prostitute, according to court documents. In 2004, a 43-year-old man picked her up in Nashville for sex and drove her to his home, the documents say.

At one point, Ms. Brown said, she thought he was reaching for a gun to kill her. She later shot him in his sleep and fled, taking money and guns, the documents say. In 2006, a jury found her guilty of first-degree murder and aggravated robbery.