In Katko v. Briney, for example, the plaintiff was injured by a spring gun while trespassing on the defendants property. [2] The defendant had set up No Trespassing signs after ten years of trespassing and housebreaking events, with the loss of some household items. Windows had been broken, and there was messing up of the property in general. The defendants had boarded up the windows and doors in order to stop the intrusions and finally had set up a shotgun trap in the north bedroom of the house. One defendant had cleaned and oiled his 20-gauge shotgun and taken it to the old house where it was secured to an iron bed with the barrel pointed at the bedroom door. It was rigged with wire from the doorknob to the guns trigger so would fire when the door was opened. The angle of the shotgun was adjusted to hit an intruder in the legs. The spring could not be seen from the outside, and no warning of its presence was posted. The plaintiff, Katko, had been hunting in the area for several years and considered the property abandoned. He knew it had long been uninhabited. He and a friend had been to the house and found several old bottles and fruit jars that they took and added to their collection of antiques. When they made a second trip to the property, they entered by removing a board from a porch window. When the plaintiff opened the north bedroom door, the shotgun went off and struck him in the right leg above the ankle bone. Much of his leg was blown away. While Katko knew he had no right to break and enter the house with intent to steal bottles and fruit jars, the court held that a property owner could not protect an unoccupied boarded-up farmhouse by using a spring gun capable of inflicting death or serious injury. In Katko, there is an intentional tort. But what if someone trespassing is injured by the negligence of the landowner? States have differing rules about trespass and negligence. In some states, a trespasser is only protected against the gross negligence of the landowner. In other states, trespassers may be owed the duty of due care on the part of the landowner. The burglar who falls into a drained swimming pool, for example, may have a case against the homeowner unless the courts or legislature of that state have made it clear that trespassers are owed the limited duty to avoid gross negligence. Or a very small child may wander off his own property and fall into a gravel pit on a nearby property and suffer death or serious injury; if the pit should (in the exercise of due care) have been filled in or some barrier erected around it, then there was negligence. But if the state law holds that the duty to trespassers is only to avoid gross negligence, the childs family would lose, unless the state law makes an exception for very young trespassers. In general, guests, licensees, and invitees are owed a duty of due care; a trespasser may not be owed such a duty, but states have different rules on this

Suppose in the Katko v. Briney case that instead of setting such a device, the defendants had simply let the floor immediately inside the front door rot until it was so weak that anybody who came in and took two steps straight ahead would fall through the floor and to the cellar. Will the defendant be liable in this case? What if they invited a realtor to appraise the place and did not warn her of the floor? Does it matter whether the injured person is a trespasser or an invitee?