NASHVILLE - When she was just 16, Cyntoia Brown climbed into a pickup truck on Murfreesboro Pike with a stranger, drove to his home, got into his bed - then shot him in the back of the head with a .40-caliber handgun as he lay naked beside her.
Brown, now 28, is serving a life sentence at the Tennessee Prison for Women for the murder of Johnny Mitchell Allen, a 43-year-old Nashville real estate agent.
She will be eligible for parole sometime after her 69th birthday.
Brown has never denied her crime. She has said that she was forced into prostitution by a violent boyfriend. She believed the man who picked her up was reaching for his gun when she killed him.
"I shot him," she said shortly after the crime. "I executed him."
But Brown's life sentence - and the practice of sentencing young people to a lifetime behind bars for even the most heinous of crimes - has drawn increased scrutiny in Tennessee and nationwide as a wave of scientific studies shows that adolescents lag behind adults in development of the parts of the brain that regulate aggression, abstract thinking and long-term planning. Other research has shown the impact of early childhood traumas on brain development.
Those studies have been cited by the U.S. Supreme Court, which issued a pair of rulings in recent years that require states to review life without parole sentences. Since 2014, at least 24 states have enacted new measures requiring an automatic review of life sentences imposed on teens after they have served a certain number of years - ranging from 15 to 40 years after sentencing.
In Tennessee, 183 people are serving life sentences for crimes committed when they were teens. The Supreme Court's rulings have had no impact. That's because state law already includes a mandatory review after 51 years - a length of time that advocates call a "virtual life sentence."
"A life sentence in Tennessee is basically life without parole," said Kathy Sinback, court administrator for the Juvenile Court of Metropolitan Nashville and Davidson County.
As a public defender 10 years ago, Sinback was appointed to represent Brown and has helped lead efforts in Tennessee to change the law to require teens sentenced to life get a mandatory 15- or 20-year review of their sentences. Such a review would allow Brown, who has since been called a model prisoner, mentors other female prisoners and received her associate degree from a Lipscomb University in-jail program in December, the chance to have her sentence reviewed at age 31 or 36.
"You are basically taking a kid at age 14 or 15 or 16 and making a decision about the rest of their life based on who they are at that age, and they're not developed human beings at that time," Sinback said. "You have kids at their peak of poor judgment, impulsivity and lack of development and we're taking that one thing that they do and locking them into sentences that are going to last for the rest of their lives."
Those sentences also come with a huge price tag to taxpayers. At more than $27,000 per year to house an average prisoner in Tennessee, incarcerating individuals sentenced to life as a teen is costing taxpayers more than $4.9 million each year.
But the movement to review sentences has drawn criticism from victims' family members and survivors of teen violence.
The National Organization of Victims of Juvenile Murderers has criticized advocates for eliminating life sentences for juvenile offenders as "lavishing all their resources on convicted murderers."
"We are not denying the premise that teenage perpetrators are impacted by toxic stress and events in their life, but we do believe juveniles have to be held accountable for their actions," said Cathy Gurley, executive director of Nashville-based victims rights group You Have the Power.
"The results are the same whether the person committing the crime is 16 or 60."
Of the 183 people serving life sentences for crimes committed as teenagers, five men and one woman were sentenced for crimes committed when they were 14; 26 were 15 when they committed those crimes; and 49 were 16. Fourteen are women.
The longest-serving inmate is Melvin Lockett, convicted in 1964 at age 15 for first-degree murder in the stabbing death of an unemployed laborer in Knox County. Lockett told police at the time of his arrest that he killed the man because the man was the first white person he and his friends saw after watching a white boy slash an African-American boy in a street fight.
The most recently sentenced is Zachary Davis, a Hendersonville teen sentenced to life in prison last year for the first-degree murder and bludgeoning death of his mother in 2012 when he was 15.
Brown, the teen girl, went to trial in 2006. During her murder trial, testimony included the fact she had been raped multiple times in her young life and had been born to a mother who admitted drinking heavily throughout her pregnancy. Brown had been in and out of the custody of the Department of Children's Services for years. At the time of the crime, she was living in a Trinity Lane motel room with her boyfriend, who profited from Brown's prostitution.
During roughly the same period as Brown's crime, trial and conviction, the U.S. Supreme Court issued a series of rulings that drew on a growing body of research into the adolescent brain. In 2005, the Supreme Court banned the use of capital punishment for juveniles.
In 2010, the court banned the punishment of life without parole for juveniles who had not been convicted of homicide.
In 2012, the court ruled that mandatory life without parole sentences for juveniles violate Eighth Amendment prohibitions against cruel and unusual punishment. In January, the Supreme Court ruled that its 2012 decision applied retroactively to individuals who had already been sentenced for crimes they committed as teens.
"Allowing those offenders to be considered for parole ensures that juveniles whose crimes reflected only transient immaturity - and who have since matured - will not be forced to serve a disproportionate sentence in violation of the Eighth Amendment," Justice Anthony Kennedy wrote in the court's 6-3 majority decision.
Twenty-four states enacted new laws after the court's 2012 ruling to require mandatory minimum sentences for teens convicted of homicide to give them a chance at parole after serving time that ranged from 15 to 40 years. Sixteen of the 31 states that allowed for life without parole do not have any prisoners serving life sentences for crimes committed as teens.
But the decision applies only to life sentences where there is no possibility of parole or automatic review of a sentence after a period of time. In Tennessee there is an automatic review after 51 years, a period advocates consider a virtual life sentence.
Advocates in Tennessee failed earlier this year to get a bill approved that would have required a review of a life sentence by the original sentencing court after 15 years.
A chance at parole does not mean someone will get out of prison, said Josh Rovner, state advocacy associate for The Sentencing Project, based in Washington, D.C.
"A chance at parole is sometimes an illusion," Rovner said.