Trespass

[1] Through the evolution of the common law in various jurisdictions, and the codification of common law torts, most jurisdictions now broadly recognize three trespasses to the person: assault, which is "any act of such a nature as to excite an apprehension of battery";[2] battery, "any intentional and unpermitted contact with the plaintiff's person or anything attached to it and practically identified with it";[2] and false imprisonment, the "unlawful obstruction or deprivation of freedom from restraint of movement".

[4][5] Since CompuServe Inc. v. Cyber Promotions, Inc.,[6] various courts have applied the principles of trespass to chattel to resolve cases involving unsolicited bulk e-mail and unauthorized server usage.

[11][12] Generally, it is not necessary to prove harm to a possessor's legally protected interest; liability for unintentional trespass varies by jurisdiction.

"[15] Generally, and as defined by Goff LJ in Collins v Wilcock,[16] trespass to the person consists of three torts: assault, battery, and false imprisonment.

[17] A person commits tortious assault when they engage in "any act of such a nature as to excite an apprehension of battery [bodily injury]".

[2] In some jurisdictions, there is no requirement that actual physical violence result—simply the "threat of unwanted touching of the victim" suffices to sustain an assault claim.

In the United States, the American Law Institute's Restatement of Torts provides a general rule to determine liability for battery:[25] An act which, directly or indirectly, is the legal cause of a harmful contact with another's person makes the actor liable to the other, if: Battery torts under Commonwealth precedent are subjected to a four point test to determine liability:[26] False imprisonment is defined as "unlaw[ful] obstruct[ion] or depriv[ation] of freedom from restraint of movement".

[38] Conveniently, the American Law Institute's Restatement (Second) of Torts distills false imprisonment liability analysis into a four-prong test: Depending on the jurisdiction, corporal punishment of children by parents or instructors may be a defense to trespass to the person, so long as the punishment was "reasonably necessary under the circumstances to discipline a child who has misbehaved" and the defendant "exercise[d] prudence and restraint".

If a plaintiff participates in a sporting activity in which physical contact is ordinary conduct, such as rugby, they are considered to have consented.

This is not the case if the physical contact went beyond what could be expected, such as the use of hand gun during a fistfight, as in Andrepont v Naquin,[43] or where the injuries were suffered not from the plaintiff's participation in the sport but inadequate safety measures taken, as in Watson v British Boxing Board of Control Ltd.[44] Where the plaintiff and defendant voluntarily agree to participate in a fight, some jurisdictions will deny relief in civil action, so long as the injuries caused are proportionate: "in an ordinary fight with fists there is no cause of action to either of [the combatants] for any injury suffered".

[45] Other jurisdictions refuse to recognize consent as a defense to mutual combat and instead provide relief under the doctrine of comparative negligence.

A physician, "treating a mentally competent adult under non-emergency circumstances, cannot properly undertake to perform surgery or administer other therapy without the prior consent of his patient".

[50] In those cases where the patient does not possess sufficient mental capacity to consent, doctors must exercise extreme caution.

[13] Exceptions exist for entering land adjoining a road unintentionally (such as in a car accident), as in River Wear Commissioners v Adamson.

William Blackstone's Commentaries on the Laws of England articulated the common law principle cuius est solum eius est usque ad coelum et ad inferos, translating from Latin as "for whoever owns the soil, it is theirs up to Heaven and down to Hell".

For instance, drilling a directional well that bottoms out beneath another's property to access oil and gas reserves is trespass,[76] but a subsurface invasion by hydraulic fracturing is not.

In the United States, United States v. Causby (1946) limited landowner domain to the space below 365 feet (111 m),[83] Justice William O. Douglas reasoned that, should it find in the landowners' favor and accept the "ancient doctrine that at common law ownership of land extend[s] to the periphery of the universe—Cujus est solum ejus est usque ad coelum", "every transcontinental flight would subject the operator to countless trespass suits".

[84] Thirty-one years later, in Bernstein of Leigh v Skyviews & General Ltd,[85] an English court reached a similar conclusion, finding an action for trespass failed because the violation of airspace took place several hundred meters above the land: "If the Latin maxim were applied literally it would lead to the absurdity of trespass being committed every time a satellite passed over a suburban garden.

Justification by law refers to those situations in which there is statutory authority permitting a person to go onto land, such as the England and Wales' Police and Criminal Evidence Act 1984, which allows the police to enter land for the purposes of carrying out an arrest, or the California state constitution, which permits protests on grocery stores and strip malls, despite their presenting a general nuisance to store owners and patrons.

[96] Jus tertii is where the defendant can prove that the land is not possessed by the plaintiff, but by a third party, as in Doe d Carter v Barnard.

[100] Necessity does not, however, permit a defendant to enter another's property when alternative, though less attractive, courses of action exist.