Federal prosecutors said yesterday that they will not prosecute a suspended Miami policeman who fatally shot a black man in Miami's Overtown ghetto area in 1982, setting off two days of racial violence.

U.S. Attorney Stanley Marcus said there was "insufficient evidence" that Officer Luis Alvarez violated the civil rights of Nevell Johnson Jr., 20, when he shot him to death in a video arcade.

"After reviewing all the statements, testimony, laboratory analysis and polygraph examinations, much of the testimony was determined to be untrustworthy," Marcus said.

Last March, Alvarez was acquitted by an all-white jury on state manslaughter charges. Alvarez's attorneys argued that he fired in self-defense after finding a gun in Johnson's waistband; prosecutors charged that Alvarez acted with gross negligence.

Marcus said that an examination of the evidence from the earlier state trial of Alvarez "tended to show Officer Alvarez's actions had been criminal because he had acted negligently in shooting Johnson."

But he said the federal civil rights statutes would have applied in the case only if it could be proved that "at the time the police officer fired his weapon, he knew, or should have known, that the force was unreasonable or unnecessary. It is not enough to show that the officer was grossly negligent or that he panicked and made an unwise decision."

Marcus said federal officials obtained and reviewed all of the interviews, files and notes of the local police investigation.