A convicted murderer who became a jailhouse pal of subway gunman Bernard Goetz is scheduled to testify against Salvatore “Sammy Bull” Gravano at his upcoming trial for the 1980 murder of a corrupt NYPD detective, Peter Calabro, Gang Land has learned.

The witness, Felipe Garcia, 51, has been behind bars most of his adult life. He befriended Goetz in 1989 when the mild-mannered electronics engineer was jailed on weapons charges, five years after Goetz used an unlicensed gun to shoot four young men who surrounded him on a subway train and asked him for money.

Garcia claims that while he and Gravano were housed at a special federal prison unit for cooperating witnesses in the early 1990s, he heard Sammy Bull make an off-hand remark about the Italian province another inmate had come from, Calabria. In hindsight, Garcia says, that has convinced him – and New Jersey prosecutors – that Gravano was involved in the Calabro killing. You can’t make this stuff up.

It won’t be the first time Garcia has stepped forward as a jailhouse snitch. Authorities don’t advertise this kind of knowledge, but by Gang Land’s count prosecutors have used information Garcia has obtained from fellow inmates at least four times in both state and federal trials. He’s testified in Manhattan and the Bronx, helping authorities win murder convictions in both counties. Now he’s headed to Hackensack, N.J., where Gravano is tentatively slated to go on trial in May.

“If he’s got any kind of information about Sammy, Sammy better be scared,” a lawyer who has come in contact with Garcia said. “He’s like a super snitch.”

In 1989, while he and Goetz were housed together on Rikers Island, federal prosecutors used tape-recorded conversations Garcia had made two years earlier with a mob associate of Genovese soldier Federico “Fritzy” Giovanelli to help convict the mobster and two others of federal murder charges in the 1986 killing of Detective Anthony Venditti. Those convictions were later reversed.

Sources said New Jersey authorities are planning to use Garcia to back up their claim that Gravano – then an up-and-coming Gambino soldier from Brooklyn with three mob hits under his belt – hired a serial killer from the Garden State, Richard “The Iceman” Kuklinski, to kill Calabro in Saddle River, N.J., on the snowy night of March 14, 1980.

According to the Bergen County prosecutor, John Molinelli, Sammy Bull was nearby and communicating with Kuklinski by walkie-talkie when The Iceman blew away Calabro with a shotgun as he drove home from work.

Gravano, who has admitted roles in 19 mob murders and is now serving 20 years for trafficking in ecstasy, has denied any role in Calabro’s killing.

“Not guilty, and they know it,” he growled at his arraignment two years ago.

The turncoat Gambino underboss was charged with the slaying in 2003, some two years after Kuklinski first claimed to have killed the rogue cop. He did so in an HBO special, “The Iceman Confesses.”

On February 25, 2003, four days after Gravano was arrested, there was an intriguing development in a seemingly unrelated federal murder case in Brooklyn that, on closer inspection, was directly related to the murder charges against Sammy Bull.

Lawyers cited the arrest as new evidence that Robert Bisaccia, a New Jersey-based Gambino capo who had been convicted on Gravano’s testimony, warranted a new trial. Bisaccia, 69, had been a longtime inmate at the same state facility as Kuklinski, also 69, and was due to begin serving a life sentence in federal prison six months later.

That all seemed a trifle suspicious to us, so Gang Land noted our suspicions to Michael Mordaga, the chief of detectives for Mr. Molinelli, and asked if he knew that Kuklinski and Bisaccia had been inmates together for 10 years and that the new charges against Gravano had been cited in a motion for a new trial for Bisaccia.

Mr. Mordaga said he was unaware of that, but would check it out and get back to us. He never did, and did not respond to a call from Gang Land this week.

Garcia is apparently angling to sell his story. According to sources and correspondence between him and Goetz that Gang Land has obtained, Garcia is seeking to get Penthouse Magazine to buy his tales of hanging out in prison with the infamous subway shooter.

In a letter in which he commiserated about Garcia’s “legal problems,” Goetz advised that it was “probably best” for him to “take the $20,000 from Penthouse, although it will probably disappear quickly. … You should be able to resell your story in a couple of years anyway.”

In his letter, Goetz deferred to Garcia’s well-established expertise in dealing with his legal difficulties: “You know how to handle them better than I do.”

Garcia and Goetz have remained friendly since they met behind bars 15 years ago. At the time, Goetz, a slim white man who had shot four young black men in an incident that fueled already volatile racial tensions around the city and in its jails, had a “strong desire to survive” his incarceration and “wanted protection,” according to law enforcement sources.

Garcia, described by one law enforcement source as “an imposing, well-built 6-footer,” provided him that protection, according to a second law enforcement source.

“He is a very smart guy, a cut above the rest you meet in prison,” Goetz told Gang Land, adding that Garcia spent “several years in Orlando, Fla., living a rather decent life” after winning his release from prison, but that his life went downhill when he returned to New York.

When Gang Land asked about Garcia’s dealings with Penthouse, Goetz said he couldn’t recall and ended the conversation. Penthouse did not return numerous calls for comment.

Garcia, who was prosecuted under a new name, is now serving 12 1/2 to 25 years in an upstate New York prison in connection with his latest case, the killing of an East Harlem supermarket clerk who was shot to death on August 4, 2001. He was convicted of conspiring to kill Kevin Medina, 25, allegedly for $2,400.

Even though he was convicted of murder conspiracy, Garcia did pretty well. His first trial ended in a hung jury. At his second trial, a jury acquitted him of murder, for which he would have faced 25 years to life.

If Garcia’s tall tale that a reputed remark by Gravano about the Italian ancestry of another inmate in a unit of cooperating witnesses enables the professional “super snitch” to earn another early release from prison, Goetz did offer some sage advice in his letter.

“You know,” wrote the one-time subway gunman who on his Web site now advocates vegetarianism and a fondness for squirrels, “you really have to limit your contact with shady people when you are outside jail.”

The assistant prosecutor handing the case, Wayne Mello, and Gravano’s lawyer, Anthony Ricco, declined to comment about the case.

This column and other news of organized crime will appear later today on www.ganglandnews.com.