On April 1, 2003, about 1630 eastern standard time, a Mooney M20C, N2652W, registered to an individual, collided with a ground marshaller during taxi from landing at Lakeland Linder Regional Airport, Lakeland, Florida, while on a 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed and no flight plan was filed. The airplane received minor damage and the private-rated pilot was not injured. The ground marshaller received serious injury. The flight originated from Sarasota, Florida, the same day, about 1545. The pilot stated he landed on runway 9 left and taxied west on taxiway "D". As he approached the intersection of taxiway "D" and runway 5-23, he encountered a ground marshaller waving 2 orange wands. The ground marshaller was standing such that the left wingtip would clear him by 18 inches. The marshaller, who was facing east, began waving his wands and back stepping to the west. As the marshaller was positioned at the airplanes 10:30 position, he, the marshaller, turned 180 degrees toward the west and bent down from the waist. His back was toward the wing and his face was down toward the pavement. The marshaller continued walking toward the west and turned his head to face another marshaller. The pilot turned to face the direction the airplane was taxing. He then heard a loud bang and the airplane rotated to the left about 15 degrees. He immediately countered with right rudder and turned left onto runway 5-23 and stopped. He looked back and saw the ground marshaller on the ground parallel to runway 5-23, with his head facing the approach end of runway 5. The ground marshaller stated N2652W approached the point he was working, runway 5-23 and taxiway "D". The sign on the airplane indicated the pilot was going to aircraft camping. He signaled him through the intersection, straight ahead. He had eye contact with the pilot and the pilot acknowledged his signal. The ground marshaller stated he turned 110-130 degrees to signal the motorcycle rider that the aircraft was going to aircraft camping. At this point, he was struck and became unconscious. A witness stated the airplane was moving at a normal taxi speed as it approached the intersection of runway 5-23 and taxiway "D". The ground marshaller made signal contact with the pilot and determined the pilot's destination. The marshaller made a 90-degree turn to tell the witness, who was on a motorcycle, where to lead the airplane. The ground marshaller's back was to the airplanes outboard left wing. As the airplane continued taxiing, the left wing struck the ground marshaller in the back, knocking him forward. The left wing then struck the ground marshaller in the back of the head, knocking him to the ground. Another witness stated the marshaller read the sign on the windshield on N2652W to verify the airplanes destination and then flagged the airplane on by. She heard the pilot give the engine excess throttle and then the airplane appeared to veer to the left. The marshaller had already began to turn and walk away when the left wing of the airplane hit him on his right side from the back. He was sent tumbling across runway 5-23.