Stephens (D) was the owner of a slate quarry near a river. A flood caused much of the quarry rubbish to wash into the river. Navigation of the river was obstructed by the debris from the quarry. D was indicted on two nuisance counts for obstructing the navigation of the river. At trial, D offered to prove that the obstructions were done by his employees against his wishes. The judge did not allow that evidence at trial. D was convicted and appealed.