Sean Bell, who had been spending his last night as a single man partying, was killed in a barrage of 50 police bullets outside a strip club.

The three police officers indicted in the shooting were to go on trial Monday in a case that has sparked protests and debate over excessive force and police conduct in New York City.

Bell's fiancee was expected to be the first witness at the trial, and she has said she plans to be in court every day.

"I feel like I need to know. I need to know why this happened," said Paultre Bell, who had her maiden name legally changed after her fiance's death. "I wake up one day and my world is turned upside down. I have to know why this happened; my family deserves to know."

Sean Bell, 23, was killed Nov. 25, 2006, hours before he was to marry the mother of his two children. He and two friends were confronted by undercover officers investigating reports of drugs and prostitution.

Detective Michael Oliver fired 31 shots, including the one that killed Bell. Detective Gescard Isnora squeezed off 11 rounds, and Detective Marc Cooper fired four times. Oliver and Isnora have pleaded not guilty to manslaughter; Cooper has pleaded not guilty to reckless endangerment.

Police union officials and defense lawyers have said the detectives believed Bell and his friends were going to get a gun, though no weapon was found. The officers opened fire after the car the three men were in lurched forward, bumped Isnora and slammed into an unmarked police minivan, authorities said.