False imprisonment or unlawful imprisonment occurs when a person intentionally restricts another person’s movement within any area without legal authority, justification, or the restrained person's permission. Actual physical restraint is not necessary for false imprisonment to occur. A false imprisonment claim may be made based upon private acts, or upon wrongful governmental detention. For detention by the police, proof of false imprisonment provides a basis to obtain a writ of habeas corpus.

Under common law, false imprisonment is both a crime and a tort.

Imprisonment.

Within the context of false imprisonment, an imprisonment occurs when a person is restrained from moving from a location or bounded area, as a result of a wrongful intentional act, such as the use of force, threat, coercion, or abuse of authority.

Detention that is not false imprisonment.

Even when a person is involuntarily detained, not all acts of detention amount to false imprisonment. The law may privilege a person to detain somebody else against their will. A legally authorized detention does not constitute false imprisonment. For example, if a parent or legal guardian of a child denies the child's request to leave their house, and prevents them from doing so, this would not ordinarily constitute false imprisonment. False imprisonment requires an intentional act, and an accidental detention will not support a claim of false imprisonment.

Complete restraint.

'Imprisonment is, as I apprehend, a total restraint of the liberty of the person, for however, short a time, and not a partial obstruction of his will, whatever inconvenience it may bring on him.' There must be complete restraint, therefore, if there are alternative routes that can be taken this is not false imprisonment. Such as in Bird v Jones  where the claimant wanted to walk over Hammersmith bridge but the defendant had cordoned off the public footpath, however, this did not constitute false imprisonment because, through using a longer route, the claimant could have still reached their destination.

Therefore, if there is a means of escape, this is not false imprisonment. There must be no reasonable means of escape and you may be compensated for any damages caused in order for you to escape reasonably. However, if you have not taken a reasonable route of escape/reasonable action you will not be awarded damages.

The claimant does not need to be aware they are being imprisoned.

It is still false imprisonment even where the claimant does not know at the time. So secretly locking someone in a room is false imprisonment. It may also be false imprisonment where a person is rendered unconscious, for example, by being punched (also a battery), or when their drink is spiked by drugs (also willful harm or negligence), because their freedom of movement is thereby restricted. For example, in the case of Meering v Grahame-White Aviation  the claimant was told to stay in an office because property was going missing and if they tried to leave the office they would have been stopped. This was held to be a false imprisonment even though the claimant did not know they were being imprisoned.