Definition
To imprison is to confine a person or restrain their liberty. The term operates in two distinct legal registers:
1. Criminal/penal context: To place a person in a prison, jail, or other custodial facility as punishment following conviction or as pretrial detention. This is the primary modern legal usage.
2. Tort/civil context: To unlawfully confine or restrain a person's freedom of movement, whether in an actual prison or by any other means — including physical force, threat, or assertion of authority. In this sense, a person can be "imprisoned" in a locked room, a vehicle, or any bounded space without access to a lawful exit. This broader usage underpins the tort of false imprisonment.
Both senses share a core idea: a person's liberty of movement is bounded without their meaningful consent. The criminal sense requires lawful authority; the civil sense is often triggered precisely when that authority is absent or exceeded.
Common Language
Modern common usage (Wiktionary): To put in or as if in prison; confine somebody against their will.
Historical common usage (Webster's 1913): To put in prison or jail; to arrest and detain in custody; to confine. Also used figuratively: to limit, restrain, or confine in any way.
The common and legal definitions largely overlap, but the gap matters at the edges. In ordinary language, "imprison" conjures a jail cell. In law, the term reaches any total restraint of freedom of movement — a locked office, a detained car, a person held by threat of force in an open field. Researchers who read the term through its common meaning may underestimate the breadth of the civil cause of action.
Common Confusion
IMPRISON vs. DETAIN vs. ARREST: These terms are frequently used interchangeably in colloquial and even legal writing, but they carry distinct meanings. To arrest is to take a person into legal custody, typically invoking formal authority. To detain is broader and includes temporary restraints short of formal arrest. To imprison, in its criminal sense, generally implies a more lasting or formally ordered confinement. In the tort context, however, "imprison" is the operative term of art for any complete restraint — even one lasting only minutes. A brief detention can constitute imprisonment for false imprisonment purposes even though it would not constitute criminal confinement.
Why It Matters in Research
The word "imprison" is deceptively simple but carries significant research traps.
First, scope creep across time: Historical sources consistently define the term expansively — "to restrain liberty in any way" — but modern researchers often encounter the word in statutes and cases that use it in the narrow penal sense only. Context determines which meaning controls. An 18th- or 19th-century treatise using "imprison" may be speaking to what we now call false imprisonment; a modern sentencing statute uses the same word to mean incarceration only.
Second, the criminal/civil divide: The same physical act of confinement can give rise to both criminal liability (unlawful imprisonment as a criminal offense) and civil tort liability (false imprisonment). These are analytically separate claims with different elements, different defenses, and different damages. Research in one body of law does not automatically transfer to the other.
Third, wrongful conviction claims: A distinct and evolving area of law covers claims by persons who were lawfully imprisoned following conviction but whose convictions are later overturned. These claims — sometimes called wrongful imprisonment or malicious prosecution claims — are structurally different from classic false imprisonment tort claims and are governed by different rules in most jurisdictions. Conflating the two in corpus research produces misleading results.
Fourth, the word's breadth in historical pleading: In common law pleading, the writ of trespass vi et armis included "imprisonment" as a recognized injury separate from battery. Researchers working in historical court records and plea rolls will encounter "imprisoned" as a specific allegation that tracked this pleading convention, not merely as a descriptive term.
Historical Dictionary Support
The four shelf sources are in close agreement. Black's (both editions) and Burrill use nearly identical language: "to put in a prison; to put in a place of confinement" followed by the expansive clause "to confine a person, or restrain his liberty, in any way." Bouvier is slightly more compact but consistent: "to confine; to put in prison; to detain in custody."
The alignment across sources on the broad definition is notable. All four sources resist limiting "imprison" to placement in a formal penal institution. Burrill's inclusion of cross-references to "Imprisonare" and "Imprisonment" signals that the term was understood as part of a cluster of related legal concepts, not a standalone synonym for incarceration.
What the historical dictionaries do not do is draw the criminal/civil distinction with any precision. They define the act, not its legal consequences. A researcher relying solely on these entries would have the right descriptive scope but would need to consult case law and treatises to understand how "imprison" functioned differently in tort pleading versus criminal law versus habeas corpus proceedings.
Jurisdictional Note
The broad common law definition — any complete restraint of liberty — applies across U.S. jurisdictions for tort purposes, but the specific elements and defenses for false imprisonment claims vary by state. Criminal statutes defining "unlawful imprisonment" or "criminal restraint" as offenses differ significantly in how they grade the severity of the offense based on duration, method, or intent.
Encyclopedia Cross-Reference
False Imprisonment (The Law Mind Criminal Law Encyclopedia, criminal_43)
Intentional Torts -- Persons -- False Imprisonment (The Law Mind Torts & Personal Injury Encyclopedia, torts_91)
Wrongful Conviction and Imprisonment Claims (The Law Mind Torts & Personal Injury Encyclopedia, torts_200)