Convicted murderer Cyntoia Brown must spend the next 51 years in prison before she can be eligible for release, a panel of appeals court judges ruled on Thursday.
Brown, now 30, was 16 when she shot and killed a Nashville man who paid her for sex in 2004.
She will be 81 before she is eligible to be released from prison.
Brown initially filed an appeal in 2012, arguing that the mandatory life sentence was too harsh. She cited a 2012 opinion by the US Supreme Court that said mandatory sentences for juvenile offenders violated the US Constitution.
But on Thursday, 5 justices ruled that defendants like Brown who are convicted of first-degree murder after July 1, 1995, and sentenced to life imprisonment, can't be eligible for release from prison before serving more than 5 decades.
The 5 justices were unanimous in their decision.
Prosecutors say Brown fatally shot 43-year-old Johnny Allen in his home in 2004. Brown claimed she shot Allen in self-defense after they got into his bed and he began touching her under the covers.
She told police she believed Allen was reaching for a handgun when she shot him.
Prosecutors say Brown stole Allen's wallet, several firearms and his pickup truck and drove to a Walmart parking lot where she had a friend pick her up. She later bragged to friends about the murder.
Prosecutors say Allen was sleeping in his bed when he was shot in the back of the head execution style.
During her appeal trial, Brown told a judge that her pimp, a 24-year-old man named Cut-throat, regularly choked, beat and sexually abused her.
"He would explain to me that some people were born whores, and that I was one, and I was a slut, and nobody'd want me but him," she said in court.
Brown's attorneys never introduced evidence of a brain disorder and a test that showed she had a low IQ, according to the Associated Press.
Brown's case drew national attention when celebrities such as Rihanna (pictured right), T.I. and Kim Kardashian used their social media platforms to rally public support for her.
"Did we somehow change the definition of #JUSTICE along the way??" Rihanna wrote in a post on Instagram in Nov. 2017.
Kim Kardashian tweeted in Nov. 2017:
"It's heart breaking to see a young girl sex trafficked then when she has the courage to fight back is jailed for life! We have to do better & do what's right."