Solitary confinement is a controversial form of punishment used in prison. Prisoners who are placed in solitary confinement will spend up to 23 hours a day in a cell with no human contact except prison staff. It has been called a barbaric form of punishment by its opponents due to its negative impact on the prisoner's mental health.

On the most part prisoners are not put into solitary confinement because of their crimes. They are usually placed in solitary confinement for some act of violence that was committed inside the prison. Prison officials say that it is the most violent and dangerous criminals that are placed in solitary confinement. If a prisoner is placed in solitary confinement it is usually because they are a danger to other prisoners. A prisoner can also be placed in confinement if his or her own safety from other prisoners is in danger. This is known as protective custody.

The cell used for the confinement can sometimes be around the same size as your average bathroom. In 24 hours there may be one hour of exercise outside of the cell. There will be no contact with the outside world in any form, although prisoners may receive mail. Prisoners will not usually be allowed to watch television or make telephone calls.

Statistics have shown that in the United States there are around 25,000 prisoners serving sentences in solitary confinement. Many prisoners have served out 20-year sentences in this manner. The majority of the prisoners in solitary confinement have been there for over five years.

A worrying report states that many of these dangerous prisoners are led straight from the confinement cell to the prison gates once their sentence is finished. There is no treatment or counseling for them before they are released back into public life. In Texas in 2005, 1,458 solitary confinement prisoners were released straight from their cell into the general public once their sentence had expired. Many of these prisoners have spent a number of years in solitary confinement and are then simply released. This type of confinement has been shown to bring on certain mental illnesses such as depression. Officials have stated that to release these prisoners with no therapy beforehand can have detrimental affects and danger to the public is substantial.

Many states in the US are now implementing some form of anger management and therapy sessions to the prisoners. Some states have implemented good behavior privileges to prisoners in solitary confinement. Many states also have panels of officials who now decide who can be let out of confinement and back into the prison population. The American Civil Liberties Union and Human Rights Watch are campaigning for an end to long-term solitary confinement sentences.