A number of UN standards and principles regulate the area of custodial and non-custodial measures. These instruments provide some guidelines on how to prohibit and prevent torture.179 The CAT has regularly asked whether prison regulations were in agreement with the Standard Minimum Rules for the Treatment of Prisoners, as Committee members have expressed the view that they consider the application of these rules to be important.180 However, the CAT has not as yet been as clear on the issue as the Human Rights Committee. The Human Rights Committee, in its individual complaints procedure and a general comment, has gone further by stating that the conditions of imprisonment in general must be in compliance with the Standard Minimum Rules. Depending on the level of development in a State, the Human Rights Committee has been inclined to give States some leeway, but the most important norms must always be complied with.181 The CAT has emphasised that governments must exercise supervision of all places in which persons can be detained or deprived of liberty and of all regulations to which such persons are subject. This must be done systematically.182 Prison inspection must be carried out, preferably without prior notice183, and the supervision must be separate from police and judiciary.184 In this context, the CAT has expressed satisfaction with the presence of, and supervision by, the International Committee of the Red Cross185 or other non-governmental organisations186 or independent national human rights commissions.187 Each State Party shall ensure that its competent authorities proceed to a prompt and impartial investigation, wherever there is reasonable ground to believe that an act of torture has been committed in any territory under its jurisdiction. Features: Prompt and impartial investigation, ex officio investigation Interpretation States Parties are obliged to take immediate action when they have reasonable grounds to believe that torture and other acts of cruel, inhuman, and degrading treatment (the latter as regulated in Article 16 §1) have been committed within their jurisdiction. The decision on whether to conduct an investigation is not discretionary.188 The authorities have the obligation to proceed with an investigation ex officio, whatever the origin of the suspicion, since the obligation to start an investigation is independent of the submission of a complaint in the sense of Article 13.189 One member of the CAT has commented that “…allegations emanating from a respected non-governmental organisation certainly constituted ‘reasonable ground’…” in the sense of Article 12.190 II. INDIVIDUAL ANALYSIS OF ARTICLES 1–16 OF THE CONVENTION 2. ANALYSIS OF SUBSTANTIVE PROVISIONS Article 12 51