CAT/C/40/2 page 6 the Subcommittee to any place under its jurisdiction and control where persons are or may be deprived of their liberty, either by virtue of an order given by a public authority or at its instigation or with its consent or acquiescence.10 10. States parties furthermore undertake to grant the Subcommittee unrestricted access to all information concerning persons deprived of their liberty and to all information referring to the treatment of those persons and to their conditions of detention.11 They are also required to grant the Subcommittee private interviews with persons deprived of liberty without witnesses.12 The Subcommittee has the liberty to choose the places it wants to visit and the persons it wants to interview.13 Similar powers are to be granted to national preventive mechanisms, in accordance with the Optional Protocol.14 D. Preventive approach 11. The work of the Subcommittee is guided by the principles of confidentiality, impartiality, non-selectivity, universality and objectivity, in accordance with article 2.3 of the Optional Protocol. The report on a visit is part of the dialogue between the Subcommittee and the authorities aimed at preventing torture and other cruel, inhuman or degrading treatment or punishment. The report on a visit to a State party is confidential until such time as it is made public in accordance with the provisions of the Optional Protocol.15 12. Whether or not ill-treatment occurs in practice, there is always a need for States to be vigilant in order to prevent it. The scope of preventive work is large, encompassing any form of abuse of people deprived of their liberty which, if unchecked, could grow into torture or other cruel, inhuman or degrading treatment or punishment. Preventive visiting looks at legal and system features and current practice, including conditions, in order to identify where the gaps 10 OPCAT, Articles 4 and 12 (a). 11 OPCAT, Article 12 (b) and 14 paragraph 1 (a) and (b). 12 OPCAT, Article 14 paragraph 1 (d). 13 OPCAT, Article 14 paragraph 1 (e). 14 OPCAT, Articles 19 and 20. 15 OPCAT, Article 16,2. The SPT shall publish its report, together with any comments of the State Party concerned, whenever requested to do so by the State Party. If the State Party makes part of the report public, the SPT may publish all or part of the report. If the State Party refuses to co-operate with the SPT or to take steps to improve the situation in the light of the SPT’s recommendations, the SPT may request the CAT to make a public statement or publish the SPT report, after the State Party has had an opportunity to make known its views.