Solitary confinement

Solitary confinement is a punishment or special form of imprisonment in which a prisoner is denied contact with any other persons, though often with the exception of members of prison staff. It is considered by some a form of psychological torture. It is usually cited as an additional measure of protection from the criminal.

It is also used as a form of protective custody and to implement a suicide watch.

Solitary confinement is colloquially referred to in American English as the 'hole', 'lockdown', the 'SHU' (pronounced 'shoe') or the 'pound', and in British English as the 'block' or the 'cooler'.

Use and criticism
Those who accept the practice consider it necessary for prisoners who are considered dangerous to other people ("the most predatory" prisoners), those who might be capable of leading crime groups even from within, or those who are kept 'incommunicado' for purported reasons of national security. Finally, it may be used for prisoners who are at high risk of being attacked by other inmates, such as pedophiles, celebrities, or witnesses who are in prison themselves. This latter form of solitary confinement is sometimes referred to as protective custody.

In the US Federal Prison system, solitary confinement is known as the Special Housing Unit (SHU),. California's prison system also uses the abbreviation SHU, but it stands for Security Housing Units. In other states, it is known as the Special Management Unit (SMU), pronounced.

Opponents of solitary confinement claim that it is a form of cruel and unusual punishment and torture because the lack of human contact, and the sensory deprivation that often go with solitary confinement, can have a severe negative impact on a prisoner's mental state that may lead to certain mental illnesses such as depression or an existential crisis    and death.

Currently, there is no empirical evidence which supports the hypothesis that supermax prisons, which house prisoners assigned to solitary confinement, reduce gang presence or violence inside prisons and increase public safety. One study found that prisoners released in Washington in 1997, when controlled for recidivism variables such as age and criminal history, were more likely to commit felonies or violent crimes if they had been assigned to a supermax facility during their incarceration.

Solitary confinement as a disciplinary measure for prisoners in Europe was largely reduced or eliminated. In 2004, only 40 out of 75,000 inmates held in Britain and Wales were placed in solitary confinement cells.