The LAPD is RUMORED to have started gathering x-ray generation devices of various kinds to 'fry' individual targets video and camera film.
Both video, still, and slide film is vulnerable to overexpose when exposed to radiation, especially x-rays. It is rumored amoung several photographers and police groups that the LAPD may have a few small-hand held x-ray generators they can target at an individuals camera and destroy the evidence inside without having to go through the trouble of confinscating or destroying the camera.
As far as this reporter is aware these should not effect digital cameras.
Stay safe, if you are carrying important footage (possiblity of it being used against the police in court or the media) then stay away from police and drop the incriminating evidence off at a safe location.
CARRY ALL FILM NOT IN YOUR CAMERA IN AN X-RAY SAFE BAG! These can be purchased at film stores (you can also put your camera in them to protect the film inside it, if you havent finished the roll inside) and are commonly used for protecting film against x-ray machines at airports.