On July 28, 1996, at 1415 central daylight time, a Piper PA-28- 151, N44059, operated by a private pilot collided with a fence during an off airport forced landing in New Melle, Missouri. The pilot stated that he was having trouble controlling the pitch attitude of the airplane which resulted in the forced landing. The airplane was substantially damaged. The pilot was not injured and the passenger received minor injuries. The flight was operating in visual meteorological conditions and no flight plan was filed. The airplane departed Chesterfield, Missouri, at 1400 cdt. The pilot reported that shortly after takeoff the airplane started to nose-up. He reported he applied forward pressure on the control yoke and adjusted the manual trim. The nose of the airplane continued to rise and the pilot suspected a "micro burst" so he applied full power and enriched the mixture. He reported that after 30 seconds, he had to maintain 15 to 20 pounds of pressure on the control yoke to keep the airplane in a nose level attitude. He reported having to hold the yoke approximately 2 inches from its forward stop. The pilot stated he determined that it was not a weather problem so he elected to make an off airport landing. The pilot initiated a descent to a farm field but reported that he was too high and fast to land in the open field. He made a turn to parallel a road. The airplane was landed between two fence posts which resulted in both wings separating from the fuselage. The nose of the airplane contacted a gate. Post accident inspection of the airplane revealed the elevator trim switch wiring shorted causing the trim motor to activate resulting in the trim traveling to the full nose up position. The pilot reported the switch had been broken for "many years" but he had not disconnected the wiring between the motor and the switch.