A criminal suspect who has been charged with or is likely to be charged with criminal offense may be held in prison if he or she is denied or unable to meet conditions of bail, or is unable or unwilling to post bail. A criminal defendant may also be held in prison while awaiting trial or a trial verdict. If found guilty, a defendant will be convicted and may receive a custodial sentence requiring imprisonment.
As well as convicted or suspected criminals, prisons may be used for internment of those not charged with a crime. Prisons may also be used as a tool of political repression to detain political prisoners, prisoners of conscience, and "enemies of the state", particularly by authoritarian regimes. In times of war or conflict, prisoners of war may also be detained in prisons. A prison system is the organizational arrangement of the provision and operation of prisons.
Prison food refers to the meals served to prisoners while incarcerated in correctional institutions. While some prisons prepare their own food, many use staff from on-site catering companies.
An example of a meal from a state prison is as follows:
- 3-4 ounces of meat
- half a cup of vegetables
- three-quarters of a cup of a starch
- three-quarters of a cup of salad with dressing
- 1 bread item
- 1 beverage
- 1 dessert
Prison cells are usually about 6 by 8 feet in size with steel or brick walls and one solid or barred door that locks from the outside. Many modern prison cells are pre-cast. Solid doors may have a window that allows the prisoner to be observed from the outside. Furnishings and fixtures inside the cell are constructed so that they cannot be easily broken and are anchored to the walls or floor. Stainless steel lavatories and commodes are also used. This prevents vandalism or the making of weapons.