An undercover New York City police detective accused of taking part in a motorcyclists-versus-driver melee is now on trial.

Detective Wojciech Braszczok (VOY'-chehk BROOSH'-chahk) faces top-level assault charges in the September 2013 attack on an SUV driver while he was off-duty.

Assistant District Attorney Josh Steinglass said Monday that Braszczok and a co-defendant took part in the violence because the victim wouldn't yield to "hordes of bikers." The driver required stitches after the beating.

A judge will determine the case. The officer has been suspended.

Eleven men were indicted after the melee. The others have pleaded guilty to charges including assault and riot.

Defense attorney John Arlia says his client was acting as a policeman who had just seen an SUV crush a biker. He says his client did not go on the attack.