Under California law, if a vehicle driver or passenger opens a door and causes a collision with another vehicle, the one who opens the door is deemed to be at fault.
Factually, if the door hit the side (as opposed to the front) of your vehicle, the facts imply the person who opened the door SHOULD HAVE seen your vehicle in time to avoid the accident.
Thus, you should not have to pay damages to the other driver. If you have insurance, you must report this incident to your insurer immediately so they can investigate the accident and deal with the other driver and his insurer (assuming he has insurance). You should also consult an attorney about this matter.
Answered on Aug 15th, 2012 at 12:13 PM