At 0819 Pacific time, the Experimental aircraft impacted a residence following an uncontrolled descent; the airplane was destroyed by impact forces and a post-crash fire. The Airline Transport pilot, who also was the aircrafts builder and registered owner, was fatally injured; three people on the ground sustained minor injuries. A combination of instrument and visual conditions prevailed along the route, from Torrance, Calif., to Chino, Calif.; the flight was conducted under IFR. The pilot was cleared to climb to 5000 feet and the airplanes Mode C transponder return indicated 5300 feet msl before ATC lost radar contact. According to a witness, the airplane came out of 600-foot ceiling in a 75-degree nose-down attitude and impacted about 100 yards from the witnesss location. Local-area pilot weather reports (PIREPS) at the time of the accident included cloud tops at 2000 feet msl and 2200 feet msl.