VEHICLE WAS BEING PREPARED TO BACK OUT OF LEVEL GARAGE ONTO DRIVEWAY WITH MILD DOWNHILL SLOPE. VEHICLE WAS STARTED, EMERGENCY BRAKE RELEASED AND AUTOMATIC TRANSMISSION PLACED IN REVERSE, DRIVER'S FOOT ENGAGED BRAKE. DRIVER REALIZED WALLET WITH DRIVER'S LICENSE WAS LEFT INSIDE HOUSE. TRANSMISSION PLACED IN PARK, DRIVER REMOVED FOOT FROM BRAKE AND EXITED VEHICLE. VEHICLE NOT NOTED TO BE MOVING WHEN DRIVER EXITED. DRIVER ENTERED HOUSE THROUGH GARAGE ENTRY, RETRIEVED WALLET. WHEN GARAGE WAS RE-ENTERED VEHICLE WAS BACKING OUT OF GARAGE ONTO DRIVEWAY ON ITS OWN. DRIVER ATTEMPTED TO CATCH UP TO VEHICLE ON FOOT AND ATTEMPT TO REGAIN CONTROL. VEHICLE BACKED DOWN FULL LENGTH OF DRIVEWAY (APPROX. 100 FEET) AND BACKED ACROSS ROAD AND DOWN FAIRLY STEEP EMBANKMENT ON OTHER SIDE OF ROAD. VEHICLE THEN BACKED INTO A LARGE TREE ABOUT 10-15 FEET FROM ROAD AND ABRUPTLY STOPPED, AND AN ADJACENT TREE WAS SIDE-SWIPED BY THE REAR/LEFT SIDE OF THE VEHICLE. NO PROPERTY DAMAGE OCCURRED, SCANT DAMAGE TO 2 LARGE TREES. DRIVER ASSESSED THE DAMAGE, RE-ENTERED THE VEHICLE. DRIVER CANNOT DEFINITIVELY RECALL WHAT GEAR THE TRANSMISSION WAS IN WHEN VEHICLE WAS RE-ENTERED. DRIVER WAS ABLE TO RE-START THE VEHICLE AND MOVE IT ACROSS THE ROAD AND BACK ONTO DRIVEWAY. *TR