Definition
A trespasser is a person who enters or remains on another's land, or interferes with another's personal property, without legal right or permission. More broadly, under older formulations, a trespasser is any person who commits an unlawful act — or performs a lawful act in an unlawful manner — to the injury of another's person or property.
The term operates across two distinct legal contexts:
1. TORT LAW — TRESPASS TO LAND: A person who enters, crosses, or causes something to enter another's real property without the owner's consent or legal justification. Intent to enter is sufficient; the trespasser need not know the land belongs to another. Actual harm is not required.
2. TORT LAW — TRESPASS TO CHATTELS / CONVERSION: A person who unlawfully takes, interferes with, or exercises dominion over another's personal property.
3. CRIMINAL LAW: A person who enters or remains on property in violation of a criminal statute prohibiting such conduct, typically requiring notice or warning before criminal liability attaches.
The duty of care owed to a trespasser by a landowner is a distinct and significant question in premises liability — historically minimal, though modern law has carved out important exceptions, particularly for child trespassers under the attractive nuisance doctrine.
---
Common Language
Modern common usage (Wiktionary): One who trespasses; an interloper.
Historical common usage (Webster's 1913): One who commits a trespass; a transgressor of the moral law; an offender; a sinner.
The gap matters. In ordinary and historical religious usage, "trespasser" carried broad moral weight — the word appears in the Lord's Prayer to mean simply a wrongdoer or sinner. Legal usage is narrower and more technical: it attaches to a specific relationship between a person and property, and the legal consequences (particularly the duty of care a landowner owes) depend on whether someone qualifies as a trespasser versus a licensee or invitee. A person can be a trespasser in the legal sense without any moral fault, and a moral wrongdoer may not be a trespasser at all.
---
Common Confusion
TRESPASSER vs. LICENSEE vs. INVITEE: These three categories govern the duty of care owed by a landowner to persons on the property. The distinctions are critical in premises liability research and are frequently collapsed or misstated in historical sources. A licensee has permission to enter, express or implied; an invitee enters by invitation for the owner's benefit or as a member of the public. A trespasser has neither permission nor legal right. The duty owed ascending from trespasser to licensee to invitee increases substantially, and confusing the categories will produce wrong results in any negligence analysis.
TRESPASSER AB INITIO: A separate doctrine — noted in Rapalje & Lawrence — under which a person who enters land with legal authority but subsequently abuses that authority is deemed a trespasser from the beginning (ab initio). This is not the same as an ordinary trespasser and the doctrine is largely obsolete in modern law. Researchers encountering the phrase in historical materials should treat it as a distinct concept requiring separate analysis.
---
Recognized Forms
/SUBTYPES
CHILD TRESPASSER (ATTRACTIVE NUISANCE): Children who trespass onto land containing artificial conditions that pose an unreasonable risk of harm occupy a specially protected category. Landowners may owe a duty of reasonable care toward child trespassers that does not extend to adult trespassers.
TRESPASSER AB INITIO: One who enters with authority — legal process, license, or right — and then exceeds or abuses that authority. Historically treated as a trespasser from the moment of entry, not merely from the moment of abuse.
CONTINUING TRESPASSER: A person who initially enters with permission but remains after that permission is revoked or expires. Refusal to leave following a demand converts a licensee into a trespasser.
---
Why It Matters in Research
The most significant research trap with "trespasser" is the premises liability context. The landowner's duty — and therefore the entire negligence analysis — turns on correctly categorizing the entrant. Historical cases frequently use "trespasser" loosely, and the rigid tripartite classification (trespasser/licensee/invitee) is a common law construct that evolved unevenly across jurisdictions. Some states have collapsed or modified the categories by statute or court decision, so a rule stated in one jurisdiction's cases may not transfer cleanly.
The criminal trespass and civil trespass meanings are legally independent. A person can be civilly liable for trespass to land without committing criminal trespass (particularly where criminal statutes require notice), and criminal trespass statutes vary so widely that findings in criminal cases should not be imported into civil analysis without care.
Trespasser ab initio is an archaic doctrine that surfaces regularly in older reports. It was criticized heavily through the 20th century and is rarely applied today, but it appears often enough in historical sources — and is cited by Rapalje & Lawrence — that researchers working in pre-20th century materials need to recognize it without assuming it states current law.
The duty-to-trespassers question intersects with constitutional takings and civil rights doctrine in limited circumstances — particularly where government actors are involved or where patterns of enforcement raise equal protection issues. Researchers should be alert to these intersections when the landowner is a public entity.
---
Historical Dictionary Support
The historical dictionaries agree on the core: a trespasser is one who commits a trespass, whether by unlawful entry onto land or unlawful interference with property. But they differ usefully in emphasis.
Black's focuses on the physical acts — unlawful entry onto land or forcible taking of personal property — which reflects the dictionary's orientation toward the most litigated scenarios.
Bouvier's offers the most analytically useful historical definition: a trespasser is one who does a lawful act in an unlawful manner, as well as one who does an outright unlawful act. This captures the trespasser ab initio problem and reflects the broader common law conception of trespass as encompassing technical violations, not just deliberate intrusions. Bouvier's also correctly identifies that legal authority — whether from the owner or from law — defeats trespasser status, and that any defect in that authority may revive it.
Burrill's entry is of limited value for this term; it addresses the French root of "trespass" rather than the legal status of a trespasser, and its utility here is primarily etymological.
Rapalje & Lawrence's entry is fragmentary in the source material but notably cross-references trespasser ab initio — a reminder that 19th-century practice treated that doctrine as sufficiently established to warrant its own entry. The doctrine's prominence in historical dictionaries is in inverse proportion to its modern vitality.
What the historical dictionaries collectively miss: the modern premises liability framework. The duty of care owed to trespassers — a central question in contemporary tort research — is not meaningfully addressed in any of these sources because the systematic tripartite classification of entrants developed primarily through late 19th and early 20th century case law.
---
Jurisdictional Note
A significant minority of jurisdictions, led by California, have abolished or substantially modified the trespasser/licensee/invitee distinction in favor of a general reasonable care standard applicable to all entrants. Researchers working in those jurisdictions should not assume that cases relying on trespasser status as a duty-limiting category state current law. The attractive nuisance doctrine for child trespassers is widely recognized but varies in its specific elements across states.
---
Encyclopedia Cross-Reference
criminal_67: Criminal Trespass — The Law Mind Criminal Law Encyclopedia
torts_105: Intentional Torts — Property and Economic — Trespass to Land — The Law Mind Torts & Personal Injury Encyclopedia
torts_106: Intentional Torts — Property and Economic — Trespass to Chattels — The Law Mind Torts & Personal Injury Encyclopedia
---