In “Cop Hunter,” co-written with “Midnight Express” author William Hoffer, some cops really are criminals. Or is it viceversa? Officers who turn crook are nothing new, but in New York in the late ’60s, overworked police recruiters let genuine career criminals slip through background checks. Murano, an Internal Affairs investigator, snared these impersonators by adopting personae of his own: a two-bit hood, a hit man and (a Pirandello touch) a crooked cop. Not content to mimic wise-guy gestures–thumbnail flicked against teeth means “Bleed to death!”–he reimagined the inner man with the zeal of a Method actor; his “Vinnie Mu” was a crude joker with a secret sadness. Murano came to love his alter ego, but after two stress-related heart attacks, “Vinnie Mu was laid to rest before he killed Vincent Murano.”

Murano admits enjoying “the preposterous, squalid society of the criminal class.” So did Philadelphia police detective Frank Friel, coauthor (with journalist John Guinther) of Breaking the Mob (306 pages McGraw-Hill. $19.95). Friel didn’t work undercover; he used to drop over and chat about mob history with the likes of tiny Harry (the Hunchback) Riccobene. Friel never forgot such people were “public menaces,” but he also had an anthropologist’s fascination with folkways and a novelist’s eye for colorful characters and comic scenes. “Longy gives me 20 [thousand dollars] if’n I off you, Harry,” a not-too-bright hit man tells Riccobene. “Ah, go an’ kill Longy instead,” says Harry. The hit man, an ex-football player, picks him up by the lapels. “I can kill you right now, you little assbag,” he says. “Nah, nah,” says the everthrifty Riccobene. “You don’t kill me. You go kill Longy and then you come back. We’ll talk about it then.” The hit man gave up. He didn’t kill “Longy,” either, figuring “he’d never get a dime out of Harry.”

Friel’s great triumph was putting away the psychopathic Nicodemo Scarfo, the first Mafia don ever convicted of first-degree murder. The few old guard Philly mobsters Scarfo left alive must have been relieved; they’d deemed him “wild-eyed, untrustworthy and unneccesarily violent.” These men had been “killers, narcotics dealers, extortionists, leg breakers,” says Friel, but they hadn’t “made the streets run with blood.” By the end of the book, we may not feel justice triumphed- too many thugs pull too little time–but we do feel equilibrium was restored.

Even this cold comfort is missing from Cop Shot (303 pages. Putnam. $21.95), New York Daily News columnist Mike McAlary’s account of the 1985 assassination of Edward Byrne, a young cop guarding a drug witness. New York’s upstart crack lords make Scarfo seem temperate: Byrne may have been killed because another cop had hassled a kingpin for drinking beer on the street. The murder outraged cops not because it broke the law–that’s what criminals do–but because it broke the rules. N.Y.P.D. detective Eddie Granshaw had known how to deal with old-style mobsters, he hadn’t even carried handcuffs. “Look,” he’d say when making a collar, “we’re in the same business. You did what you had to do. Now I’m doing what I have to do. Let’s be professional about this.” The Byrne case was different–and it was Granshaw’s last stand. “This is the crime that changes us,” said a brother officer after the killers were sentenced. “Yeah, well,” said Granshaw, “I’m getting out.”