Community policing is the hot crimefighting tool of the 1990s. President Clinton’s crime law is putting 100,000 more cops on the beat – and even Republicans applaud that idea. But the success of community policing depends on a fragile bond of trust between police and residents – and a corruption case can sunder that quickly. Five of the ““Dirty 30’’ officers were assigned to a community-policing unit that took tips on drug locations and dealers from residents. But instead of making busts, they allegedly made profits. ““It was a deep betrayal,’’ says pastor Lenton Gunn Jr. of the St. James Presbyterian Church. ““It will be a long time before the policemen in the 30th will be trusted.''

No betrayal was more heinous than that of Kevin Nannery. Residents liked the 33-year-old sergeant, who used to show up at block parties, and arranged police vans to take kids to the circus or the park. ““That boy had a hell of a kinship with everybody in the neighborhood,’’ says Charles, a retired schoolteacher who is now too frightened to give his last name.

In the summer of 1993, Charles says, he gave Nannery the names of some local drug dealers. The next day, one of them approached him and said it ““ain’t cool’’ to talk to the cops. According to investigators, the sergeant ran an eight-man gang known as Nannery’s Raiders, which, among other things, faked calls to 911 to give themselves a pretext for breaking into dealers’ apartments and stealing their money and drugs. ““Until the bitter end, you thought, Oh naw, man, not Nannery,’’ says Charles. ““He’s with us.''

Most Harlem residents are still ardent fans of community policing. Sandra Carter, principal of a private school, wants more cops like Officer Norman Peterson, who stands outside as kids come and go, keeping dealers away by his very presence. ““Nobody wants to be mad at the police,’’ says local activist Raymond Curtis. But with cops like Nannery around, they have also learned to be wary.