There are three different things that, when they exist, excuse the person who committed the crime from being charged. What are they ?

Martin acampora purchased a shotgun at a garage sale years ago, never used the weapon, and did not know of any defects in it. his 31-year-old son marty borrowed the shotgun to go duck hunting. as marty attempted to engage the safety mechanism, the shotgun fired. the force of the shotgun’s firing caused it to fall to the ground and to discharge another shot, which struck marty in the hand. classify the bailment in this case. what duty of care was owed by the bailor in this case? is martin liable to his son for the injury?