As far as New Jersey is concerned, abriggs is absolutely correct with a single exception. We do not have a duty to act if we are off duty, even if we are in uniform. The only exception to this rule is if you obtained a speciality license plate from the state that identifies you as an "EMT" or "EMT-P". P.S. I forgot to mention that this exception only applies if you are in your vehicle and witness an emergency. If you are nowhere near your car and witness something you once again do not have a duty to act.