An off-duty undercover New York City police detective accused of taking part in a motorcyclists-versus-SVU melee says he didn't intervene because he feared for his safety.

Detective Wojciech Braszczok (VOY'-chehk BROOSH'-chahk) testified in his defense Tuesday. He's charged with assault in the September 2013 attack on SUV driver Alexian Lien (lee-EHN').

A judge, not a jury, is hearing the case.

Eleven men were indicted in the confrontation, which occurred on a Manhattan highway. Lien ran over a motorcyclist, paralyzing him, before he was pulled from his Range Rover and beaten.

Lien wasn't charged.

Braszczok says he didn't have a gun or a badge and didn't think anyone would believe he was a police officer. He says he didn't intend to harm the driver and fled.