Trespass

In modern law the word trespass is used most commonly to describe the intentional and wrongful invasion of another's real property. An action for trespass can be maintained by the owner or anyone else who has a lawful right to occupy the real property, such as the owner of an apartment building, a tenant, or a member of the tenant's family. The action can be maintained against anyone who interferes with the right of ownership or possession, whether the invasion is by a person or by something that a person has set in motion. For example, a hunter who enters fields where hunting is forbidden is a trespasser, and so is a company that throws rocks onto neighboring land when it is blasting.

Every unlawful entry onto another's property is trespass, even if no harm is done to the property. A person who has a right to come onto the land may become a trespasser by committing wrongful acts after entry. For example, a mail carrier has a privilege to walk up the sidewalk at a private home but is not entitled to go through the front door. A person who enters property with permission but stays after he has been told to leave also commits a trespass. Moreover, an intruder cannot defend himself in a trespass action by showing that the plaintiff did not have a completely valid legal right to the property. The reason for all of these rules is that the action of trespass exists to prevent breaches of the peace by protecting the quiet possession of real property.

In a trespass action, the plaintiff does not have to show that the defendant intended to trespass but only that she intended to do whatever caused the trespass. It is no excuse that the trespasser mistakenly believed that she was not doing wrong or that she did not understand the wrong. A child can be a trespasser, as can a person who thought that she was on her own land.

Injury to the property is not necessary for the defendant to be guilty of trespass, although the amount of damages awarded will generally reflect the extent of the harm done to the property. For example, a person could sue birdwatchers who intruded onto his land but would probably receive only nominal damages. A farmer who discovers several persons cutting down valuable hardwood trees for firewood could recover a more substantial amount in damages.

Trespassers are responsible for nearly all the consequences of their unlawful entry, including those that could not have been anticipated or are the result of nothing more wrongful than the trespass itself. For example, if a trespasser carefully lights a fire in the stove of a lake cabin and a fault in the stove causes the cabin to burn down, the trespasser can be held liable for the fire damage.

Courts have had to consider how far above and below the ground the right to possession of land extends. In United States v. Causby, 328 U.S. 256, 66 S. Ct. 1062, 90 L. Ed. 1206 (1946), the U.S. Supreme Court held the federal government liable for harm caused to a poultry business by low-altitude military flights. The Court concluded that because the airspace above land is like a public highway, ordinary airplane flights cannot commit trespass. In this case, however, the planes were flying below levels approved by federal law and regulations, so the government was held responsible. Its activity was a "taking" of private property, for which the FIFTH AMENDMENT to the U.S. Constitution requires just compensation.

It may be a trespass to tunnel or mine under another person's property, to force water or soil under the property, or to build a foundation that crosses under the boundary line. Underground encroachments are usually an exception to the rule that no harm needs to be shown in order to prove a trespass. Generally, trespass actions are permitted only where there is some damage to the surface or some interference with the owner's rights to use her property.