The mandate and functioning of NPMs are set out in OPCAT and briefly outlined here. OPCAT recognises that people in detention are particularly vulnerable and requires States to set up a national level body that can support efforts to prevent their ill treatment. States must guarantee the functional independence of NPMs and their personnel, and take necessary measures to ensure that NPM experts have required capabilities and professional knowledge. States parties must undertake to make available to NPMs the resources necessary for their functioning.
OPCAT Article 19 outlines that national preventive mechanisms must be granted at the minimum the power:
(a) To regularly examine the treatment of the persons deprived of their liberty in places of detention as defined in article 4, with a view to strengthening, if necessary, their protection against torture and other cruel, inhuman or degrading treatment or punishment;
(b) To make recommendations to the relevant authorities with the aim of improving the treatment and the conditions of the persons deprived of their liberty and to prevent torture and other cruel, inhuman or degrading treatment or punishment, taking into consideration the relevant norms of the United Nations;
(c) To submit proposals and observations concerning existing or draft legislation.
To facilitate these powers, States must grant NPMs:
(a) Access to all information concerning the number of persons deprived of their liberty in places of detention, as well as the number of places and their location;
(b) Access to all information referring to the treatment of those persons as well as their conditions of detention;
(c) Access to all places of detention and their installations and facilities;
(d) The opportunity to have private interviews with the persons deprived of their liberty without witnesses, either personally or with a translator if deemed necessary, as well as with any other person who the national preventive mechanism believes may supply relevant information;
(e) The liberty to choose the places they want to visit and the persons they want to interview;
(f) The right to have contacts with the Subcommittee on Prevention, to send it information and to meet with it.