The detective posted $150,000 bail and left the courthouse with his hood pulled up as far as possible. He climbed into a waiting car.
Braszczok, who worked in the intelligence division, was stripped of his gun and badge after internal affairs detectives discovered he was present for at least part of the melee during a periodic motorcycle rally. Police say it was touched off when a motorcyclist and Lien's SUV bumped.
The detective initially told authorities and his union that he left without intervening, in part because of his role as an undercover. Uniformed officers, even off-duty, are expected to jump in if a crime is occurring, but rules are murkier for undercover officers who face blowing their covers.
But investigators discovered video evidence showing Braszczok punching an already damaged back window, causing it to shatter, then twice kicking the passenger side of the SUV before leaving the scene, prosecutors said.
The arrest added to the complexities of the Sept. 29 episode, which authorities say began with a reckless motorcycle group ride. More than 1,000 bikers participated.
Several bikers have been charged criminally, either with attacking Lien or his car or instigating the violent encounter.
Clint Caldwell, 32, was also charged yesterday with gang assault after prosecutors said he pulled out the shattered glass from Lien's window and reached inside the SUV. His lawyer, Raymond Colon, says there's no video that shows him with his hands inside the car.