A onetime Mafia hit man, who turned state's evidence and helped send nine mobsters to prison, has been denied prerelease furlough privileges, while all of the nine he sent up the river are already free on parole.

The turncoat Mafioso is John Patrick Tully, who now calls himself John Parker. He was an admitted killer for the Campisi mob family of New Jersey, and is serving time at the federal prison in Pleasanton, Calif., where officials say he is a changed man.

As Bureau of Prisons rules allow, Parker applied for overnight furlough privileges 15 months before his November 1981 release date. The prison's "unit team" reviewed his record and judged him an acceptable risk.

But the Plesanaton warden, for reasons he won't discuss because of privacy considerations, turned down Parker's request. When several prison officials asked for reconsideration, the application was sent to Washington.

There it was considered -- and rejected -- by an official who was once Parker's warden at a New York correctional center and had several legal runins with him -- which the warden lost. The official, Larry Taylor, says he remembered that he and Parker were in New York at the same time, but didn't recall any legal actions Parker had taken against him.