CHARLOTTE, N.C. -- A man who police call a person of interest in the slaying of a pregnant teen will spend 30 months in prison after a federal judge determined he did violate his probation.

The judge said Wednesday afternoon that he believes 15-year-old Tiffany Wright’s statements to police that she had sex on two occasions with her adoptive brother, Royce Mitchell, and that is enough to revoke his probation on a previous conviction and send him back to federal prison.

“Judge Conrad found that Royce Mitchell broke state law by committing statutory rape in having sex with Tiffany Wright,” said Edward Ryan, acting U.S. attorney.

Mitchell was charged with statutory rape on the same day that Wright was shot to death while waiting for her school bus in north Charlotte in September. Wright’s baby was delivered and died a week later.

Wright had told police that Mitchell was the father of her baby. When DNA evidence ruled Mitchell out as the child’s father, the statutory rape charge was dropped, but he remained in jail accused of violating his probation with the arrest.

Mitchell was on probation for a drug conviction in New York. Because the standard for evidence is different for probation violations, the judge was able to listen to a recording of a detective’s interview with Wright, which would not have been admissible in a rape trial because Wright could not be cross-examined.

“(Because of the interview), the court could hear it for himself and make the determination she was credible. Had we not had that recording, we wouldn’t be standing out here today,” said Thomas Cullen, assistant U.S. attorney.

“We would have much preferred that Tiffany Wright had been in the courtroom as a witness for the United States, but somebody made that impossible,” Ryan said.

Mitchell maintains he is innocent.

In the courtroom, he said, "I did not have sex with Tiffany. This is definitely a nightmare for me and my family."

Although Mitchell has not been charged in Wright’s or her baby’s death, police have said he is the only person of interest in the case.

Mitchell can appeal Wednesday’s decision or serve the 30 months, about 2.5 years, in prison.