The Optional Protocol to the Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment provides: The objective of the present Protocol is to establish a system of regular visits undertaken by independent international and national bodies to places where people are deprived of their liberty, in order to prevent torture and other cruel, inhuman or degrading treatment or punishment. [art. 1] A Subcommittee on Prevention of Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment of the Committee against Torture (hereinafter referred to as the Subcommittee on Prevention) shall be established and shall carry out the functions laid down in the present Protocol. [art. 2, para. 1] The Subcommittee on Prevention shall carry out its work within the framework of the Charter of the United Nations and shall be guided by the purposes and principles thereof, as well as the norms of the United Nations concerning the treatment of people deprived of their liberty. [art. 2, para. 2] Equally, the Subcommittee on Prevention shall be guided by the principles of confidentiality, impartiality, nonselectivity, universality and objectivity. [art. 2, para. 3] The Subcommittee on Prevention and the States Parties shall cooperate in the implementation of the present Protocol. [art. 2, para. 4] Each State Party shall set up, designate or maintain at the domestic level one or several visiting bodies for the prevention of torture and other cruel, inhuman or degrading treatment or punishment (hereinafter referred to as the national preventive mechanism). [art. 3] The Principles on the Effective Investigation and Documentation of Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment provide: 2. States shall ensure that complaints and reports of torture or ill-treatment are promptly and effectively investigated. Even in the absence of an express complaint, an investigation shall be undertaken if there are other indications that torture or ill-treatment might have occurred. The investigators, who shall be independent of the suspected perpetrators and the agency they serve, shall be competent and impartial. They shall have access to, or be empowered to commission investigations by, impartial medical or other experts. … 3. (a) The investigative authority shall have the power and obligation to obtain all the information necessary to the inquiry. The persons conducting the investigation shall have at their disposal all the necessary budgetary and technical resources for effective investigation. They shall also have the authority to oblige all those acting in an official capacity allegedly involved in torture or ill-treatment to appear and testify. … 135