The officers faced charges ranging from second-degree murder to criminally negligent homicide and reckless endangerment of bystanders.

But in Albany, race emerged as an issue from the beginning of the trial, when the defense lawyers tried to use peremptory challenges to remove three black women from the jury. Prosecutors objected, and Justice Teresi refused to remove the women. In the end, after a white woman was removed for discussing the case outside court, the jury consisted of four black women, one white woman and seven white men. In a somber daily tableau, family, friends and colleagues of the four officers sat on one side of the courtroom aisle while Mr. Diallo's parents, Mr. Sharpton, and other Diallo supporters, mostly black, sat on the other. The two sides never spoke to each other and only rarely glanced across the aisle.

Mr. Diallo, 22, worked as a peddler on 14th Street in lower Manhattan, selling videotapes, socks, gloves and other items from a spot on the sidewalk. Slightly built and genial, he was 5 feet 6 inches tall and weighed 150 pounds. He worked 12 hours a day, six or seven days a week, taking the subway from the apartment on Wheeler Avenue, which he shared with a friend and two cousins.

He had returned home around midnight on the night of the shooting and discussed a utility bill with one of his roommates. The roommate went to bed and Mr. Diallo, for reasons that are not known, went downstairs to the vestibule of the building.

At about 12:40 a.m., the four officers, all members of the Street Crime Unit, were patrolling in an unmarked car and dressed in street clothes when they turned down Wheeler Avenue. The unit had been established to patrol high-crime areas in an effort to prevent robberies, rapes, murders and assaults.

Officer Carroll was the first to notice Mr. Diallo on the stoop of the building. He testified that Mr. Diallo was acting suspiciously, peering out from the stoop, then ''slinking'' back. Mr. Diallo, Officer Carroll said, fit the general description of a serial rapist who had last struck about a year earlier. But he acknowledged on cross-examination that he could not see Mr. Diallo well enough even to determine his race.

Officer Carroll said he also suspected that Mr. Diallo might have been a lookout for a push-in robber. In any case, he told his partners he wanted to question Mr. Diallo.