Several witnesses reported that the pilot/owner had performed acrobatic maneuvers in his homebuilt airplane, including rolls, and had recently started performing loops. There were no witnesses to the accident, but on-scene evidence indicates that the airplane had impacted the ground in a steep nose-down attitude. The Volkswagen engine equipped airplane had a gravity fed fuel system which would not provide a constant supply of fuel to the engine when the airplane was inverted during acrobatic maneuvers. Evidence indicates the propeller was not turning at impact. The airplane, as certificated, was prohibited from acrobatic flight. The pilot was issued a student pilot certificate in 1983. A person who lived with the pilot for 3 yrs had recently moved from his house due to what was described as the pilot's excessive consumption of alcohol and use of marijuana. The toxicological report on the pilot showed a blood alcohol level of 0.105%, and a 0.002 ug/ml level of carboxylic acid (marijuana) was also detected in his blood.