A pair of ex-NYPD detectives allegedly serving as hired guns for a murderous mob chieftain didn’t hunt down rival hoods only. They also did the unthinkable, law enforcement sources told Gang Land, ferreting out information about a mob-busting federal prosecutor marked for death by their Mafia benefactor.

The former detectives, Louis Eppolito and Stephen Caracappa, allegedly gained access to police files of registered gun owners to obtain a Manhattan address for a then-assistant U.S. attorney, Charles Rose, whose comments had infuriated a Luchese underboss, Anthony (Gaspipe) Casso, law enforcement sources told Gang Land. The sources said the “Mafia Cops” funneled information to Casso that Rose maintained an apartment at 254 Park Ave. South.

They didn’t stop there. According to the sources, the rogue cops tried to locate the building’s main telephone box in an effort to locate and wiretap the prosecutor’s home phone. “It was not a half-hearted effort,” one source said.

In their efforts to earn the $4,000 monthly retainer that Casso allegedly paid them, sources said, the detectives also furnished Casso a post-office box that Rose had “in the Hamptons,” and they searched Department of Motor Vehicle records.

Messrs. Eppolito and Caracappa were unable to find any cars registered to Rose and failed to discover that he also maintained an apartment on the Upper East Side. “It was not for a lack of trying,” one source said.

As usual, sources said, the information the “Mafia Cops”- Mr. Eppolito is the author of a memoir “Mafia Cop” – supplied Casso, as well as the money he allegedly paid them for their services, were routed through a convicted drug dealer, Burton Kaplan, the gangster’s longtime associate. Kaplan has told the feds that Casso, then a fugitive, plotted to kill Rose in late 1991 and 1992.

Rose, who died of brain cancer in 1998, was the lead prosecutor against Casso and the leaders of four families charged with labor racketeering, stemming from their control over the lucrative replacement-window industry in New York City public housing during the 1980s.

Messrs. Eppolito and Caracappa have denied any criminal activity.

From his hideout in a wooded hamlet in Mt. Olive, N.J., Casso directed a trusted capo, George “Georgie Neck” Zappola, to stake out the Park Avenue South address to determine if Rose actually lived there, according to a secret FBI report obtained by Gang Land.

In the report – based on a 1994 interview with Casso – two FBI agents, Stephen Byrne and James Brennan, wrote: “Zappola had a photograph of Rose from a newspaper article and went to the address once or twice to try and catch sight of Rose. Zappola also went to the vicinity of the court house at Cadman Plaza in Brooklyn, to try to observe Rose in a car that could be traced.”

Frustrated by Zappola’s inability to locate Rose, Casso ordered Georgie Neck to dispatch a telephone company contact to see if “he could find a telephone line for Rose” at 254 Park Ave. South, the agents wrote.

Casso was furious at Rose, the gangster told the agents, because he believed the prosecutor was the source of information in a September 21, 1991, article in Newsday that linked the execution of an architect to the “possibility” that he had begun “an intimate relationship” with Casso’s wife after the gangster left home and became a fugitive in May 1990. The victim had been found in a stolen car a day earlier, shot in the head, chest, and leg, and stabbed numerous times in the neck and heart, clad only in a pair of boxer shorts.

In its last paragraph, the Newsday article speculated that an amorous relationship with Casso’s wife, Lillian, could have triggered the brutal slaying, quoting an unnamed investigator as saying: “Why else would you strip a guy naked before you killed him? Clearly, someone was trying to make a point.”

The article incensed Casso and his wife, the agents wrote, and each called Casso’s lawyer at the time, Gerald Shargel, to inquire about seeking a “retraction.” Casso said the lawyer advised them “to let it rest and not create a bigger issue,” since the newspaper “was not as widely read as the Daily News,” the agents wrote.

Reached by Gang Land, Mr. Shargel said he had “no recollection” of either phone call but said, “That is the advice I would have given.”

Restraint was never a Casso strong suit, however. The gangster said he enlisted “the cops” and Zappola in a murder plot because Rose had acted unprofessionally, by causing “something personal like that [to] appear in public,” the FBI agents wrote.

The alleged plot fizzled when Casso – who had been tipped about the “Windows” indictment, allegedly by Messrs. Eppolito and Caracappa, a few days before it was made public – was arrested in January 1993 after 32 months on the lam.

Sources told Gang Land that Kaplan, the prosecution’s key witness against Messrs. Eppolito and Caracappa, has confirmed details about the plot to kill Rose and that those allegations are part of a continuing investigation into the ex-detectives. Assistant U.S. Attorneys Robert Henoch and Mitra Hormozi declined to comment on the subject.

Though he was squirreled away 50 miles west of New York from mid-1990 through January 1993, Casso was plugged into every detail of the plan to locate and execute Rose, according to secret FBI reports obtained by Gang Land.

Through clandestine visits with Kaplan at the latter’s Brooklyn home, and through a complex system that employed pagers, cell phones, and public telephones, Casso kept up with a steady stream of insight from the ex-detectives and capo Georgie Neck.

Zappola, who is serving 22 years for racketeering and several murders, was occasionally used to deliver messages between Casso and Kaplan, and to chauffeur Casso back and forth to Kaplan’s home, according to a report by FBI agents Brennan and Richard Rudolph.

To contact Kaplan, Casso would page Kaplan and plug in a special code – number 47 – that would alert him to “activate a cell phone he maintained at all times.”

When they needed to speak for a “long period of time” they used public telephones, with Casso on one in a shopping mall in Rockaway, N.J., which is off Route 80 in northwest New Jersey, and Kaplan using a phone on the Staten Island side of the Verrazano Bridge, the agents wrote.

“During his discussions with Kaplan regarding ‘the cops,’ Kaplan admitted that on several occasions ‘the cops’ came to his house at night to either discuss matters or exchange money,” agents Brennan and Rudolph write.

“At some point it was agreed that they had been to Kaplan’s house too often, so instead Kaplan began going to one of the cops’ homes,” the agents wrote, adding Casso could not recall the location, but believed it wasn’t far from Kaplan’s Bensonhurst home.

“On another occasion,” the agents wrote, “Kaplan mentioned to him that one of the cops was looking to retire and go into acting in California. At another time he recalled Kaplan saying that the second cop was looking to retire.”

Mr. Eppolito, 56, retired in 1990, and has had bit roles in many movies, including “Goodfellas.” Mr. Caracappa, 63, retired in 1992. The two men were living across the street from each other in Las Vegas when they were arrested in March and charged with taking part in eight murders and three failed mob hits from 1986 through 1991 as part of a racketeering enterprise that began in 1983. They are scheduled for trial in September.

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