A man who a federal judge ruled had sex with his adopted sister has lost an appeal of his 2½ year prison sentence.

The judge ordered Royce Mitchell to jail because he decided his sexual relationship with 15-year-old Tiffany Wright violated terms of his 2007 probation on a federal drug charge.

Wright, who was eight months pregnant, was shot to death as she waited for the school bus in September 2009. Police named Mitchell a person of interest, but later concluded he wasn't involved with the killing.

But Wright told a detective that she had sex with Mitchell before she died.

Mitchell continues to deny the allegations, and Wright's lawyer said a DNA test that found Mitchell was not the baby's father proves they didn't have sex. But The Charlotte Observer reports that the U.S. 4th Circuit Court of Appeals decided that just because prosecutors couldn't independently verify Wright's allegations doesn't mean they aren't true.