He’s a mystery man at the trial of three police officers accused of killing an unarmed groom-to-be in a hail of gunfire on his wedding day _ variously referred to as the “SUV guy” and the “man in black.”

Both police and civilian witnesses have described him as a cool customer with a cold stare. The shooters say they believed he was possibly packing a gun.

His name, lawyers say, is Fabio Coicou. Beyond that, little is known about the man who was a key player in the death of Sean Bell hours before his wedding.

The witnesses have testified that Coicou and Bell menaced each other outside a Queens strip club, the scene of Bell’s bachelor party, on Nov. 25, 2006. The brief standoff is central to the undercover detectives’ explanation for why they eventually fired 50 bullets at the car carrying Bell and two friends who were seriously injured.

“The SUV guy was calm, cool and collect, right?” defense attorney Anthony Ricco asked during cross-examination of Detective Hispolito Sanchez, who posed as a strip club patron that night.

“Yes, he was.”

“The SUV guy gave a straight street stare (at Bell), like `Go ahead,’ right?”

“Yes sir.”

“And you’re thinking, `This is not good. Somebody is going to get shot,’ right?”

“Yes sir.”

Coicou disappeared into the night before the shooting began.

Detectives Michael Oliver and Gescard Isnora face manslaughter charges in the case. A third detective, Marc Cooper, is charged with reckless endangerment.

Prosecutors have portrayed the detectives as trigger-happy and poorly supervised. The defense contends the officers had witnessed Bell and his friends trade insults with Coicou and became convinced they were going to Bell’s car to get a gun.

Coicou apparently was living in Georgia when he resurfaced about a year ago to testify before a grand jury investigating the shooting. When the trial started last month, he was on the prosecution witness list _ a sign he was ready to tell his story publicly.

But he has not.

Prosecutors have declined to say when _ or even if _ he will be called to testify at the trial, now in its third week.

The officers claim the shooting began only after Isnora identified himself as a police officer and that Bell, who was behind the wheel, nearly ran over him and smashed into one of the police cars. A supervising lieutenant has testified that amid the confusion he believed his men were the ones under fire.

No weapon was found in the car.

Though they didn’t know his identity at the time, police first made note of Coicou in a report prepared immediately after the shooting.

The report describes how, while investigating allegations of prostitution at the club, undercover officers noticed “an unidentified (man) wearing all black clothing.” The man was “standing next to a black SUV with shiny rims, parked directly in front of Kalua Cabaret,” and at one point “placed his right hand inside his jacket pocket, simulating that he had a weapon,” the report said.