The pilot reported that, during cruise flight, the air traffic controller instructed him to descend from 9,000 to 4,000 feet. While performing the descent checklist, he switched fuel tanks on the Bonanza A36, and the engine subsequently lost power.
He further reported that he was certain that the engine restarted and that the event put him “behind the airplane in performing…cockpit duties.”
The next thing the pilot remembered was the controller informing him that he was flying in circles and losing altitude. The pilot thought the airplane was in a spin and tried to regain control.
After the airplane broke out of the clouds into poor visibility and snow, he chose to land in a cornfield near Parker City, Indiana. During the landing, the airplane hit trees and terrain, resulting in serious injury to the pilot.
A witness reported observing the airplane at a low altitude traveling at a high rate of speed, then it pitched up to almost vertical flight, descended, and impacted terrain.
The NTSB determined the probable cause as the pilot’s loss of airplane control while troubleshooting an engine issue in instrument meteorological conditions, which resulted in impact with trees and terrain.
NTSB Identification: CEN15LA098
This January 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.

This was no pilot. This was a panic stricken passenger who rode an otherwise normal functioning airplane into the ground. Would be best for all concerned if he never touched the controls of another airplane.
The pilot was low time (421 TT, 349 PIC, 59 in type), not fully competent with his systems, had very limited IFR experience (17 actual, 73 simulated, 15 actual + sim in his Bonanza), and evidently very dependent upon his cockpit automation (autopilot). He did not know his aircraft limitations (thought the Bonanza was a ‘utility’ category rather than ‘normal’, and perhaps other factors). He was clearly not familiar with emergency procedures, nor competent with hand flying the aircraft. Overall, the pilot appeared to be overconfident in his aircraft and abilities. The docket makes it very clear that the engine performed as designed, and that his loss of power was not due to any mechanical defect in the fuel system. “Pilot induced fuel starvation” followed by loss of control pretty much sums it up.