Article 2. Obligation to Prevent Torture 85 36  Also, the maintaining of an official (electronic) register where all detainees are systematically registered from the moment of deprivation of liberty was recommended by the Committee,83 with lawyers and relatives of those detained having access to these records.84 Unrecorded places of detention are not permissible. 37 A  worldwide study looking at the effectiveness of torture prevention measures equally concluded that procedural protections in the first moments of arrest have the greatest impact to prevent torture.85 38  In Ramiro Ramírez Martínez et  al v Mexico, the Committee has voiced its concern regarding preventive custody being implemented in military facilities, particularly its excessive duration and the lack of monitoring, as well as the number of complaints of torture by persons subjected to preventive custody, which lead to an environment that encouraged confessions obtained under torture and these being used as evidence.86 The Committee has therefore found a violation of Article 2(1). As part of the State reporting procedure, the Committee has also recommended that States parties should reduce preventive detention to an absolute minimum and consider abolishing the practice for young offenders.87 39  In the case of the State party’s failure to introduce measures to prevent torture of prisoners by or with the acquiescence of authorities, as well as prisoner-​on-​prisoner violence and in the absence of an independent prison monitoring mechanisms, the Committee has equally found a violation of Articles 2 and 11 of the Convention in the individual complaints procedure.88 3.1.2.3 Ensuring Independent Monitoring of Places of Detention 40  The Committee has stipulated that States parties should ensure that there are impartial mechanisms that visit and inspect places of deprivation of liberty.89 With the entry into force of the OP in June 2006, States parties to the CAT are provided with an excellent opportunity to open up their prisons and detention centres to more transparency and independent monitoring by both the UN Subcommittee on Prevention and so-​called National Preventive Mechanisms (NPMs). Preventive visits to places of detention have a double purpose. The very fact that national or international experts have the power to inspect every place of detention at any time without prior announcement has a strong deterrent effect by shedding light on closed institutions. At the same time, such visits create the opportunity for independent experts to examine, at first hand, the treatment of prisoners and detainees and the general conditions of detention. One may therefore conclude that the ratification of the OP by States parties to the CAT and the creation of independent national preventive mechanisms in line with OPCAT and the Paris Principles constitute important measures in the sense of Article 2(1) CAT.90 83   CAT/​C/​GC/​2 (n 1) para 13; CAT/​C/​ARM/​CO/​3 (n 72) para 11. CAT/​C/​AZE/​CO/​3 (n 72) para 11; CAT/​C/​MUS/​CO/​3 (n 73) para 10. CAT/​C/​PHL/​CO/​2 (n 72) para  7. 84   CAT/​C/​ARM/​CO/​3 (n 72) para 11; CAT/​C/​BLR/​CO/​4 (n 72) para  6. 85   Carver and Handley (eds), Does Torture Prevention Work? (Liverpool University Press 2016) 68. 86   Ramiro Ramírez Martínez et al v Mexico, No 500/​2012 (n 42) para 17.5. For State obligations to ensure conditions of detention in line with the Convention, see also Art 16, 3.4. 87   CAT/​C/​NOR/​CO/​6-​7 (n 60) para  9. 88   Hilda Mariolyn Hernández Colmenarez and Francisco Arturo Guerrero Sánchez v Bolivarian Republic of Venezuela, No 456/​2011 (n 43) para 6.7. 89 90   CAT/​C/​GC/​2 (n 1) para  13.   CAT/​C/​GC/​2 (n 1) 13. See also below Art 11 and OPCAT. Zach