POWER LIFTGATE MALFUNCTION- LIFTGATE WAS OPERATED FROM THE REAR SWITCH. UPON ACTIVATION IT ROSE ALMOST FULLY AND THEN SLAMMED DOWN ON A PERSON WHILE THEY WERE ACCESSING THE REAR CARGO AREA, INJURING THEIR NOSE AND FACE. LIFTGATE FAILED TO STOP AT OBSTRUCTION. FROM THAT POINT ON LIFTGATE FAILED TO OPEN OR CLOSE WITHOUT MANUAL INTERVENTION. VEHICLE WAS STATIONARY, ENGINE RUNNING AND MOSTLY LEVEL STREET. WEATHER HAD BEEN RAINY BUT WAS NOT RAINING AT THE TIME, 63 DEGREE TEMP. NOT SURE IF IT WAS IN PARK OR DRIVE, BUT BRAKES WERE APPLIED AND OTHER PASSENGERS WERE ENTERING THE VEHICLE. THE NEXT MORNING THE POWER LIFTGATE HAS OPERATED NORMALLY.