NTSB Probable Cause

POOR JUDGEMENT OF THE INSTRUCTOR PILOT (CFI) DUE TO HIS IMPAIRMENT FROM USE OF MARIJUANA, INADEQUATE SUPERVISION OF THE FLIGHT BY THE CFI, AND HIS FAILURE TO ASSURE THAT ADEQUATE AIRSPEED WAS MAINTAINED, WHICH RESULTED IN AN INADVERTENT STALL. FACTORS RELATED TO THE ACCIDENT WERE: THE CFI'S INADEQUATE PREFLIGHT PLANNING/PREPARATION, AND HIS FAILURE TO ASSURE THE AIRCRAFT WAS WITHIN ITS CERTIFIED GROSS WEIGHT LIMIT.