-18 “European prison administrations massively use solitary confinement.” 2.BACKGROUND 2.1. Solitary confinement: definition and purposes Solitary confinement can be broadly defined as the separation of a detainee from the general prison population. The prisoner is housed alone in a cell for the greater part of a day; international standards usually indicate 22 hours as the minimum to consider a situation as solitary confinement. However, it is important to point out that there is no unique definition for this practice; section 3.3 of this Handbook highlights the diffrent approach of the revised European Prison Rules to this specific issue. Solitary confinement is a response that the prison administration uses in a variety of prison situations.10 For this reason, it can be used in different ways: as a form of punishment for disciplinary offenses, as a protective measure for detainees finding themselves in a situation of vulnerability (e.g. sex offenders, LGBTIQ detainees, juveniles), or as an administrative tool to handle specific groups of prisoners. It can be used as a health instrument, e.g. to prevent the spread of contagious diseases. It can also be imposed by a court decision during pre-trial detention, in order to protect the undergoing investigation, or it can be the result of a court judgement, which imposes solitary confinement as part of prison sentence. Finally, in several jurisdictions there also is voluntary solitary confinement that also poses several problems from different points of view. 10. One comprehensive handbook is Sharon Shalev’s sourcebook on solitary confinement, freely available online: Shalev S (2008) A Sourcebook on Solitary Confinement. Mannheim Centre for Criminology, London School of Economics: London. online at: www.solitaryconfinement.org/sourcebook