The 24 year old unlicensed pilot made an unauthorized flight in his father's aircraft. The Cessna 337 was observed to maneuver in the vicinity of the airport at a low altitude in and out of the clouds. The aircraft was then observed to come out of the clouds left wing high and the nose fell through the horizon. The aircraft impacted on the airport and was destroyed by the impact. The pilot was fatally injured. No pre-existing mechanical malfunction was found with the aircraft. Weather was estimated to be 200 ft variable 400 ft overcast, 1 mile visibility, with rain and fog. Witnesses reported that the pilot had flown solo in this aircraft and another 337 and a Piper Cherokee also based at this airport. No record could be found to indicate the pilot had ever possessed a medical certificate or taken any FAA rating exams. Witnesses said he had received flight instruction from his father, a retired airline captain.