Three police officers went on trial today in the death of an unarmed man killed in a barrage of 50 bullets on his wedding day, with prosecutors recreating the chaos of that fateful night as they sought to portray him as the victim of reckless, trigger-happy detectives.

Lawyers for the officers didn’t dispute the degree of firepower in the now-infamous killing of 23-year-old Sean Bell. But they argued that the shooting was not excessive and that it was justified because their clients had ample reason to believe Bell and his friends were armed and dangerous as they left a Queens strip club in the early hours of November 25, 2006.

The trial occurred in a packed courtroom that lacked the theatrics of most high-profile trials, largely because the case is being heard by a judge and not a jury.

But it did become emotional at times. The woman Bell was to marry, Nicole Paultre-Bell, wept as she testified about being summoned that night to the hospital where she learned Bell was dead. Clutching a tissue, she needed about a minute to compose herself as she relived the night.

Detectives Gescard Isnora and Michael Oliver are charged with manslaughter while Detective Marc Cooper is on trial for reckless endangerment. Detective Oliver fired 31 shots — including the one that killed Bell. Detective Isnora squeezed off 11 shots, and Detective Cooper fired four times.

An assistant district attorney, Charles Testagrossa, told the judge that once the evidence is heard, “It will be clear that what happened cannot be explained away as a mere accident or mistake. It can only be characterized as criminal.”

Detective Isnora’s attorney, Anthony Ricco, said there was evidence that Bell was drunk and “out of control” as he left the strip club after his bachelor party. Witnesses overheard Bell exchange curses with another patron, and heard Bell’s friend, Joseph Guzman, say to someone, “Go get my gat,” slang for gun, Mr. Ricco said.

The lawyer said Bell, at Mr. Guzman’s urging, “tried to run over” Detective Isnora with his car after the officers confronted the members of the bachelor party and identified themselves as police. The lawyer described the car as a “deadly weapon” and “human battering ram.”

“When there is a confluence of alcohol and ignorance, there’s always a tragedy,” Mr. Ricco said.

Mr. Testagrossa said that Detective Oliver would have found there was no threat if he had “paused to reassess” while firing 31 of the shots. He emptied his clip, reloaded, and shot again.

A defense lawyer, James Culleton, estimated that it took as little as nine seconds for Detective Oliver to fire the 31 rounds from his semiautomatic pistol — even with reloading — leaving him no time to reassess.

Mr. Culleton said Detective Oliver saw Bell’s car trying to flee, then heard Detective Isnora yell, “He’s got a gun! He’s got a gun!”

The defense lawyer said Detective Oliver will testify that during the chaos, he saw Mr. Guzman starting to lift his arms. Mr. Culleton said Detective Oliver was convinced that if he hesitated, “He’d be looking down the barrel of a gun and he’d be a dead man.”

Investigators found no gun at the scene.

Outside the courthouse, a handful of noisy protesters chanted and banged on drums to show their support for the shooting victims and Bell’s family.

Before going inside, Nicole Paultre-Bell, who legally took her fiance’s name after his death, stopped to pray with Mr. Guzman, who was also shot that night, and the Reverend Al Sharpton.

In a soft voice, she mentioned their daughters, ages 5 and 1, and recounted how she met Bell in high school. He had a tattoo on his chest bearing her nickname — “Coli.”

She was not cross-examined.