On December 28, 2001, at 1329 central standard time, a Borgman Smyth Sidewinder, N133G, operated by the aircraft builder, who was not a rated pilot, collided with the terrain following a loss of control while maneuvering near a private airstrip in Independence, Kansas. The non-pilot and a pilot rated passenger were both fatally injured. The airplane was substantially damaged. The 14 CFR Part 91 flight was operating in visual meteorological conditions without a flight plan. The flight originated from Coffeyville, Kansas, exact time unknown. The accident occurred about one-quarter mile east-northeast of a private east-west airstrip. One witness reported seeing the airplane perform a touch and go at the airstrip. He then saw the airplane flying to the east, traveling slow at an altitude of about 100 feet above the ground. He reported the airplane then turned south followed by a turn back to the east-northeast. The witness reported the last bank was "very steep." He reported that during the turn the right wing (top wing) dropped and the airplane descended straight into the ground. Another witness reported seeing the airplane losing altitude as it was flying to the east. The witness reported the airplane went "straight up" and appeared as if it were making a loop prior to descending straight into the ground. The owner of the airplane who was seated in the left seat is not a certificated pilot. The owner/operator of a fixed base operator at the Coffeyville Municipal Airport reported the aircraft owner had been flying N133G. He estimated that the airplane had been flown approximately 15 to 20 times prior to the accident and the owner "usually took passengers" with him. This person also said that the owner was receiving flight instruction from a local pilot. (The local pilot was not a flight instructor and his pilot's certificate had been suspended.) Another pilot who is a Federal Aviation Administration (FAA) safety counselor also reported the owner had been flying the airplane and that he was taking flight instruction from a local pilot. The pilot rated passenger who occupied the right seat held a private pilot certificate issued on December 15, 1999. The passenger was issued a Third Class medical certificate on June 11, 1999, at which time he reported having 350 hours of flight time. Inspection of the airplane revealed the leading edges of both wings were uniformly crushed back to the main spars. The fuel tank was crushed and a strong odor of fuel was present in the area. Inspection of the airframe, flight controls and engine failed to reveal any failure/malfunction that would have resulted in the loss of control. The airplane registration was issued on August 13, 2001. The Wichita, Kansas Federal Aviation Administration (FAA) Flight Standards District Office (FSDO) received a letter dated October 22, 2001, requesting an inspection for an airworthiness certificate. According to the FSDO, they informed the owner that it would be several months before the inspection could be conducted. That inspection had not taken place at the time of the accident. Therefore, N133G did not have an airworthiness certificate at the time of the accident. Autopsies on the occupants of the airplane were performed at the Shawnee County Coroner's Office, on December 29th and 30th 2001. Toxicological samples from both occupants were sent to the FAA's Toxicology and Accident Research Laboratory, Oklahoma City, Oklahoma, for examination. The toxicological results were negative for those substances tested.