According to a recent survey, 75 per cent of NHRIs said that they receive complaints from detainees, especially those in the Asia-Pacific region (100 per cent), followed by the Americas (88.8 per cent), Africa (73.6 per cent) and Europe (57.2 per cent). Of these respondents, a total of 36 NHRIs provided statistics on complaints of torture and ill-treatment, as shown by the following regional breakdown: Complaints statistics - torture and ill-treatment 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Africa Americas Asia Pacific Europe -10 10-20 20-50 50-100 100-200 200+ No data Source: OHCHR, “Survey of national human rights institutions”. Respondents reported a wide range of issues from torture to ill-treatment, including assault and brutality by security personnel, inadequate diet, poor conditions and overcrowding, unnecessary isolation, and forced medical trials. National human rights institutions are also expected to play a more effective role and become even more visible in accordance with the Optional Protocol to the Convention against Torture, which entered into force in 2006: ■■ ■■ The Optional Protocol obliges States to set up independent national preventive mechanisms to examine the treatment of people in detention, make recommendations to Government authorities to strengthen protection against torture and comment on existing or proposed legislation. The Optional Protocol incorporates a degree of flexibility in the structure of these mechanisms and, in recent years, many countries that have ratified it have in fact designated existing NHRIs (e.g., commissions and ombudsmen) as their national preventive mechanisms. The preventive nature of the visits required under the Optional Protocol is different in purpose and methodology from other types of visits that NHRIs may conduct and, in particular, from visits to investigate or document individual complaints made by detainees. The Optional Protocol includes certain guarantees and powers that can help resolve this challenge. The Optional Protocol to the Convention against Torture provides that States parties will designate independent national prevention bodies to monitor places “where people are deprived of their liberty”, including prisons. The purpose of these monitoring bodies will be “to prevent torture and other cruel, inhuman or degrading treatment or punishment”. NHRIs may be appointed as the national preventive mechanisms, provided that they satisfy the Paris Principles. The Optional Protocol requires States to ensure that the national prevention bodies have the resources and the authority, including unlimited access to any place of detention, to carry out this responsibility. As explained in the Training Manual on Human Rights Monitoring, it is essential for monitors to “know the standards”. There are a number of standards that apply in this context, for instance: ■■ The International Covenant on Civil and Political Rights (arts. 7, 9, 10 and 11); ■■ The Convention against Torture; ■■ The Standard Minimum Rules for the Treatment of Prisoners; 121