Trotman, 38, was assigned to the 77th Precinct in Bedford-Stuyvesant when he joined the gang, providing them with police raid jackets and radios when they staged robberies.

It took Trotman one day to decide to cooperate, admitting to a litany of crimes - including robbery and a conspiracy to kill another cop.

"I couldn't believe a New York City police officer would do those things," prosecutor Jack Smith told the judge.

Then highly decorated Detective James Harkins, who retired last month, added: "From the moment I arrested Mr. Trotman, he's been completely up-front. He was carrying this guilt, and I think he was happy to get it off his chest."

Trotman allowed investigators to place a listening device in a boom box in his living room. He gathered evidence against his corrupt partner, Jamil Jordan, who was arrested but refused to cooperate. Jordan is serving 13 years.

The prosecutor said there was no excuse for Trotman's misdeeds, but they charted his downfall from the moment in 1992 when his 4-year-old son was severely shocked by a heart monitor. The boy suffered significant brain damage.

In a poignant letter to the judge, Trotman said his marriage was shattered and he began to drink. He remarried and had two more children, "but I really didn't have that thirst for life anymore. Not that I didn't love my family, but the idealistic view of protecting them ... and the line between right and wrong began to blur."

His voice shaking, Trotman told the judge he accepted full responsibility for his actions. "I can't blame anyone because I was the one who did it," he said.

Trotman spent the past five years in prison in the witness protection program. He was facing 10 years, but the judge said he hoped the light sentence would send a message to cops who go bad about the value of coming clean.