Wayne County Prosecutor Kym Worthy told the Detroit News that while she has worked on so-called innocence cases in the past, she has only agreed to release the defendants when the evidence is clear.
"In this case the evidence is not clear cut," Worthy said.
Legal researchers from the Michigan Innocence Clinic at the University of Michigan this week filed a motion calling for the release of Karl Vinson, 54, who has been locked up since 1986 for assaulting a 9-year-old girl, the News said.
The Innocence Clinic contends Vinson was the victim of inaccurate crime-lab work that was misrepresented to the jury. The organization said evidence at the crime scene proves the rapist had a different blood type than Vinson.
The News said Wednesday that Vinson has maintained his innocence while in prison; however, all of his appeals have been rejected.
Worthy said a judge would have to decide the merits of the Innocence Clinic's petition.