-28 “Solitary confinement should be used as a measure of last resort and for the shortest possible time” 3.STANDARDS 3.1. Definition of solitary confinement The definition of solitary confinement was endorsed by the Special Rapporteur on Torture by referring to the Istanbul Statement on the Use and Effects of Solitary Confinement. The Statement is the product of three days of working sessions by the most important experts in the penitentiary field, and which was presented on the last day of the International Psychological Trauma Symposium that took place in Istanbul at the end of 2007.25 In 2015, this definition of solitary confinement was included in the Mandela Rules, which state that solitary confinement is “the confinement of prisoners for 22 hours or more a day without meaningful human contact”, while prolonged solitary confinement was defined as the imposition of the measure for more than 15 consecutive days.26 At the regional level, the CPT gives a definition of solitary confinement that applies to several situations. The detainee can, for instance, “be held on his/ her own”, but the CPT underlined that its standards set for this measure also apply when the detainee is “accommodated together with one or two other prisoners”. Moreover, the CPT adds that solitary confinement can be imposed “as a result of a court decision, as a disciplinary sanction imposed within the prison system, as a preventative administrative measure or for the protection of the prisoner concerned”.27 The revised European Prison Rules (EPR) of 2020 envisage solitary confinement only as a disciplinary 25. United Nations General Assembly, ‘The Istanbul Statement on the Use and Effects of Solitary Confinement’, annex to the Interim Report of the Special Rapporteur on Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, A/63/175, 28 July 2008. 26. United Nations General Assembly, Standard Minimum Rules for the Treatment of Prisoners (Revised Mandela Rules), Resolution 70/175, A/RES/70/175, 17 December 2015, Rule 44. 27. European Committee for the Prevention of Torture, 2011, §54.