FIVE YEARS AGO, in a suburban Detroit hotel, a crime-connected Teamster official pulled a revolver with a six-inch barrel out of his coat and rammed it down my throat. For the next half-hour -- while he watched with mixed emotions over what he had done to me -- I could do little more than walk around the room, wiping tears from my eyes and spitting out blood and pieces of teeth. He later apologized, saying that he had been under enormous pressure and mistakenly thought I was there to betray him. b

The incident occurred during my first interview with the man, who was convinced that his confederates were double-crossing him. As a result of his anguish and paranoia, he had started talking privately to government officials and reporters, telling of his associates' illicit deeds while simultaneously and willingly placing his life in jeopardy. Nevertheless, he continued to talk for the next two years, sometimes openly, and proved to be a reliable source of information. Even after his violent act against me, I couldn't help but admire him. He was a brave man and sincerely sorry for his own crimes against society. Few people were surprised when he was found shot to death in December 1977.

Government informants, particularly those who flip from the underworld, are rarely appreciated for the services they provide in the war against crime. The are damned by former friends, often taunted by the press, and are always in fear for their lives. Even if their cooperation is part of a plea-bargaining defense, they still usually supply investigators with valuable intelligence or even direct evidence which can help send more dangerous people to jail. Regardless of their motives for "turning" -- self-serving or otherwise -- informants deserve better treatment than being called "canaries" and "stool pigeons," particularly if their testimonies prove credible in court.

However, there are real dangers when an informant's personal opinions, based upon little or no evidence, are accepted as absolute truths.

Jimmy Fratianno, an unlikely government informant, is the central character in Ovid Demaris' latest book, The Last Mafioso. The mob's busiest assassin on the West Coast until 1977, and, for a short period of time, one of the most powerful crime chiefs in Southern California, Fratianno, a protege of Chicago mobster John Roselli, is the highest-ranking underworld figure ever to flip. But, because of his background and the importance of his information, Fratianno is in a different category from the low-level mob operative who turns against his boss and should be examined in a more critical manner.

Although Fratianno lived by the sword, he refused to die by it, making his decision to turn state's evidence against fellow mobsters after underworld associates targeted him for contract killing. In return for his cooperation with the government -- which has proven to be invaluable in several prosecutions -- Fratianno has been given the opportunity to receive "safety and revenge."

Demaris has chronicled Fratianno's highly complicated, incredibly detailed saga with great literary style and organization. A crime reporter by profession and the author of two best-selling books on organized crime -- The Green Felt Jungle (with Ed Reid) and Captive City -- Demaris is on familiar turf writing about Fratianno's violent career.

Given that, Demaris must have wrestled with his own conscience while deciding how this murderer-turned-informant should be portrayed. Unfortunately, he chose to glamorize Fratianno and even to place him in a heroic context. That might play well with those who have a romanticized impression of gangsters, but not with others who view organized crime as a serious threat to America's institutions.

To Demaris, Fratianno "was a complex human being: He was uneducated but intelligent enough to talk with you on just about any level you chose; he could talk like a hood or like a gentleman, like a punk or a lawyer." Although that seems to be a somewhat balanced observation of Demaris' subject, it is still high praise for a cold-blooded killer.

Despite Demaris' expertise on the mob, he was essentially at the mercy of Fratianno's memory -- which the author insists was "absolutely phenomenal." When Fratianno told Demaris that he had made love to a woman five times in three hours while in his late sixties, Demaris writes it as fact -- with no harm done in this instance.

However, when Fratianno told Demaris that "Operation MONGOOSE" -- which directly involved both President Kennedy and Attorney General Robert Kennedy -- was really the code name for the CIA-Mafia plots to assassinate Fidel Castro, that was damaging to historical truth and nothing less than irresponsible journalism when printed. Demaris should have known better. The Church Committee clearly stated that "Operation MONGOOSE" was designed in 1962 to infiltrate and organize the Cuban population to incite a counterrevolution; it had nothing to do with the CIA-Mafia plots against Castro -- which began in 1960 under President Eisenhower. Neither John nor Robert Kennedy was aware of these plots until CIA officials informed the attorney general about them in 1962. Upon hearing this, Robert Kennedy was particularly outraged by the underworld's involvement. But he was assured by the CIA that the plots had ceased with the failure of the Bay of Pigs invasion in April 1961 -- when in fact they were being escalated. Incredibly enough, Demaris acknowledged this in his book. Yet, he leaves the reader with the clear impression -- based upon hearsay passed from Roselli to Fratianno -- that the Kennedys had not only authorized the plots but also approved of the mob's participation.

Such information discredits other parts of this important book and raises legitimate questions about the credibility of Fratianno and of Demaris, who trashed the Kennedys in My Story, told to him by John Kennedy's alleged mistress, Judith Campbell Exner.

Equally disturbing was Fratianno's effort to discredit the government's 66-month investigation of Jimmy Hoffa's disappearance. Based only upon a brief conversation with a now-dead Los Angeles mobster, Fratianno proclaimed that the government's top suspects -- one of whom he described as "a friend" throughout the book -- were really not involved in Hoffa's murder.

One explanation for some of the confusion in such important areas might be attributed to the liberties Demaris admittedly took with the tremendous amount of dialogue contained in the book. Some of the reconstructed conversations simply defy belief. For instance, Fratianno -- again on the late Roselli's hearsay -- promoted the implausible theory that President Kennedy's plots against Castro backfired when the Cuban leader ordered the president's assassination. Fratianno supposedly said to Roselli, who was involved in the CIA-Mafia plots against Castro, "Maybe if you had clipped him [Castro], Kennedy would still be alive." Roselli supposedly replied, "Listen, Jimmy, in this business, you can't win them all."

Considering the pressure the Kennedy administration had placed on underworld figures, like Roselli, the thought of any organized crime boss mourning the president's death is as ridiculous as this alleged conversation.

Despite some of the excellent information Fratianno has provided the government about specific crimes in specific areas, there are still grave questions as to whether he has been pulling his punches in other cases, particularly those related to the powerful Marcello organization in Lousiana which Fratianno has failed to lay a glove on.

One hopes the government will continue to challenge Fratianno's credibility, and by implication the credibility of Demaris' book, to find out whether its prized informant is telling more than he really knows or knows more than he has already told.