Lawyers for a woman who fatally shot a man who had picked her up for sex when she was 16 say it's unconstitutional to keep her in prison until she's 67.
Cyntoia Brown's lawyers filed a federal appeal, after celebrities including Rihanna and Kim Kardashian called for her release.
Brown, now 29, has been at the Tennessee Prison for Women since 2004, when she was convicted of killing the 43-year-old man.
Brown's advocates say she was a sex trafficking victim fearing for her life and wronged by the legal system. Prosecutors say Brown killed the man to rob him.
Monday's appeal cites a Supreme Court ruling against life sentences for juveniles and asserts Brown's innocence, saying she lacked the mental capacity at the time to commit murder.