While it is impossible to determine liability without knowing all the details of the case, generally dooring accidents are the fault of the vehicle occupant who opened the door into the path of the bicycle. California’s Vehicle Code 22517 states that no person is permitted to open a door of a vehicle on the side closest to moving traffic without ensuring that it is reasonably safe to do so and does not interfere with traffic movement. Part of a driver’s duty of care is to ensure that they operate their vehicle according to law, so a violation of the law is strong evidence when proving liability.