Background
The pilot, who held an instrument rating and a private certificate, filed an instrument-flight-rules (IFR) flight plan. During the flight, the pilot reported to the controller that he was operating under visual-flight-rules (VFR) at 9,500 feet.
Flight
The controller cleared the pilot to descend and maintain 9,000 feet. Shortly thereafter, the pilot requested clearance to climb to 11,000 feet. The controller informed the pilot that there were reports of icing between 12,000 and 16,000 feet. The pilot responded that he would be "on top of it." The pilot then requested clearance to climb to 13,000 feet. Not long after, the pilot reported "experiencing some precipitation" and requested clearance to descend to 11,000 feet.
Accident
Analysis conducted by Safety Board meteorology specialists indicated that the airplane likely encountered freezing rain or drizzle, which would have resulted in moderate to severe mixed icing adhering to its airframe. As the airplane descended in a right turn, it disappeared from radar. The airplane subsequently broke up in flight and impacted heavily wooded terrain.
Toxicology
Marijuana was found at the scene. Post-accident toxicological testing performed on specimens from the pilot was consistent with the use of marijuana within 3 hours of the accident.