Trespass (Norman Fr. trespasser, from tres, beyond, and passer, to go), in law, as usually defined, a wrongful act, committed with some kind of violence, and injurious to the person, property, or rights of another. Its literal meaning is precisely the same as transgression; it is a step beyond the limits of law or right. In the old law Latin the word trans-gressio was used where trespass is used in English. Formerly the two words were employed in writing and conversation with the same meaning, but now trespass is commonly used only in the legal sense, and is an important law term. Familiar examples of trespass are assault and battery, forcible entry into a house or upon lands, breaking open a door, and tearing down a fence. Such acts are in law trespasses vi et armis, or, in the English phrase now used in indictments and declarations, trespasses with force and arms. Early in the history of the law a very slight degree of violence was sufficient to constitute this offence; and soon afterward the law held that it might be committed in some cases without any actual force whatever, implying by construction the force necessary to make it a trespass vi et armis, if the act were unlawful.

Thus, for example, a peaceable entry into a house or land, with intent to take possession and oust the-true owner, was regarded as a trespass vi et armis. Soon after there grew up a large and very important class of trespasses, where there was neither actual nor constructive force. The courts in fact invented a form of action, by means of which remedies might be given for a great number of injuries, to which the law of trespass with force and arms could not be made applicable by any construction. This new legal trespass was called, in the law Latin in use when the action was first employed, trans-gressio super casum, and is now called a trespass on the case. In the days of special pleading it had become very difficult to determine whether the action by which redress was sought for in certain injuries should be trespass or trespass on the case; and if the plaintiff mistook his form of action, he wholly failed. But by recent statutes, with the rules of court and the amended practice, if a mistake be made it may be corrected without delay and without cost.

Trespass with force and arms (or trespass alone, for the latter clause is often omitted) lies when the injury complained of is itself the wrong done by the defendant; while trespass on the case lies when the injury was consequential upon the wrong done, and flowed from it indirectly. For example, trespass on the case lies for an injury sustained by the plaintiff from the defendant's sale to him of unwholesome food, as meat or wine, especially where it was the business of the defendant to sell these things. So for an injury caused by the want of skill of any person in the exercise of his profession, as a physician or lawyer. There is yet another nice and very important distinction in the law of trespass. A man may begin by doing a right thing in a right way, and then so change his course as to do a wrong thing, or a right thing in a wrong way. In some of these cases such a person thus subsequently trespassing is regarded by the law as a trespasser ab initio, or as having been a trespasser through the whole of his conduct. Thus, if, in the execution of a legal process, he does something which is distinctly illegal, the law considers that he began to act with intent to do an illegal thing, and that all of his conduct was tainted by this intention and was therefore illegal.

The doctrine is applied only where the wrong was done while in the exercise of a strictly legal right, which the injured party had no right to resist, and seems to be confined by the best authorities to the cases of an officer of the law acting under a legal warrant, and a guest at an inn.