Before takeoff, the crew indicated the flight would be for 'check rides' and that they planned to 'shoot approaches' and proceed to the practice area to do some airwork. ATC advised the pilots that the cloud bases were at 3,500 feet MSL. Elevation of the terrain (where the aircraft subsequently crashed) was 1,225 feet. Prior to the accident, witnesses saw the aircraft circling in a steep turn at low altitude. One witness reported it was circling as if to land. Subsequently, it impacted in a steep nose down, slight left wing low, attitude. Several witnesses reported that one or both engines sputtered before the aircraft crashed; however, an exam of the engines revealed no indication of a preimpact malfunction or failure. An exam of the airframe revealed the landing gear was in the extended position when the aircraft crashed. Exam of the props indicated that both engines were producing an equal amount of power. The airwork to be completed included steep turns, stalls, and flight at minimum control airspeed.