MONITORING PLACES OF DETENTION : A PRACTICAL GUIDE FOR NGOS 22 constructive working relationship, in which the points of view of the officials about their working conditions and any problems they might have identified can also be obtained. 3.2. Visiting mechanisms at the national level Monitoring detention conditions is, above all, the responsibility of the national authorities in charge of persons deprived of their liberty. Thus, Principle 29, paragraph 1, of the United Nations “Body of Principles for the Protection of All Persons under Any Form of Detention or Imprisonment” lays down: “In order to supervise the strict observance of relevant laws and regulations, places of detention shall be visited regularly by qualified and experienced persons appointed by, and responsible to, a competent authority distinct from the authority directly in charge of the administration of the place of detention or imprisonment.” Most States have established their own mechanisms for monitoring places of detention and incorporated them into their legislation and administrative regulations. In general, these are internal control mechanisms and are an integral part of the detention system. In an increasing number of countries, complementary external mechanisms also exist which seek not to supplant but to supplement the internal mechanisms. The necessity to submit places of deprivation of liberty to external independent monitoring at the domestic level was recognised by the Optional Protocol to the United Nations Convention against Torture5. This text contains an obligation for States Parties to “maintain, designate or establish (…) one or several independent national preventive mechanisms for the prevention of torture at the domestic level.” (Art. 17). The text has been adopted by the United Nations General Assembly in December 2002 and will enter into force after the 20th ratification.