As a broad general rule, property owners owe few duties to trespassers to safeguard them from injuries that may occur on their property. With respect to the duties owed to trespassers, there are two types of trespassers to consider: • The
undiscovered trespasser, to whom the property owner owes only a duty not to "trap" or wilfully harm the trespasser. • The
anticipated or
discovered trespasser. To those parties, the landowner owes a
duty of common humanity (See
British Railways Board v. Herrington)—a
duty to warn them of deadly conditions on the land which would be hidden to them, but of which the property owner is aware. For injury claims by trespassers, the concept of traps was narrowly defined. More recently, courts in some jurisdictions have engaged in some creativity, adopting a broader interpretation of a trap. A warning sign at the entrance to the land is generally sufficient to warn trespassers of possible hazards on a property or land. However, a property owner is under no duty to ascertain hazards on his property for the benefit of trespassers, and cannot be held liable for failing to discover a previously unknown hazard that injures a trespasser. In some jurisdictions an adult trespasser who is injured while on a defendant's property cannot sue under a theory of
strict liability, even if the landowner was engaged in
ultrahazardous activities, such as the keeping of
wild animals, or the use of
explosives. Instead, the trespasser must prove that the property owner intentionally or wantonly injured the plaintiff to recover. Some jurisdictions extend additional protections to children who trespass on the properly of others. For example, if there is a potentially hazardous object or condition on the land that might be attractive to young children, the trespass may be deemed "anticipated" under the doctrine of
attractive nuisance such that the child may be able to succeed with an injury claim. In some regions of the world, a property owner may use reasonable (typically meaning non-deadly) force to prevent a person from trespassing on their land, or to expel a trespasser. However, a property owner may be restricted from expelling a trespasser if doing so would expose the trespasser to a risk of serious injury. For example, a trespasser who takes shelter in a stranger's barn during a powerful storm cannot be expelled until the storm is over. ==United States==