On December 6, 1997, about 0907 central standard time, a John T. Simpson Challenger II experimental airplane, N11644, stalled into trees, then collided with the ground, in Rainbow City, Alabama. The airplane was operated by the pilot under the provisions of Title 14 CFR Part 91, and visual flight rules. Visual meteorological conditions prevailed. A flight plan was not filed for the local fight. The uncertified pilot was fatally injured, and the airplane was destroyed. Origination of the flight was a private airstrip near Rainbow City, about 0900, on the same day. Witnesses stated that the airplane appeared over the tops of the trees, flying towards them. The airplane gained altitude and lost altitude, and sounded as if it was not running well. The witnesses saw the airplane gain altitude, then stall into the trees, and nose dive into the ground. The airplane was a homebuilt Challenger II, which is a single engine, two seat airplane. It was built by John T. Simpson and co-owned by Mr. Simpson and the pilot. According to the FAA inspector, the aircraft co-owner/builder stated that the pilot was unable to control the jointly owned airplane. He stated that the pilot purchased the airplane in June of 1995, and the pilot and builder agreed to become partners in the airplane in August of 1996. Each man was supposed to get a pilot's certificate. The pilot did not get his pilot's certificate as agreed. According to the co-owner of the airplane, the pilot had no formal training in the airplane. He had about 5 hours of flight training in another airplane. A post mortem examination of the pilot was completed December 8, 1997 by the Gadsden County Medical Examiner's Office. A toxicological examination of the pilot was completed by the Federal Aviation Administration's Toxicology and Accident Research Laboratory on March 30, 1998. The results were positive for fluoxetine, norfluoxetine, nordiazepam, desipramine, bupropion, bupropion metabolite, and phentermine. All substances were found in both the liver and kidney fluid. According to the Physician's Desk Reference (PDR), fluoxetine, desipramine, and bupropion are all prescription antidepressants. Norfluoxetine and bupropion metabolite are metabolites of antidepressants. Nordiazepam is a metabolite of a prescription tranquilizer, and phentermine is a prescription stimulant used to treat obesity. All of the above medications act upon the central nervous system. The PDR lists possible side effects of the above medications as drowsiness, dizziness, anxiety, seizures, and hyperactivity.