indeed, of data on complaints received in special detention units for people suspected 346 or convicted of terrorist offenses. Effective complaints mechanisms are a crucial way to prevent torture and other ill-treatment and other misconduct, as perpetrators will more 347 likely be deterred if they know that victims can report safely. Furthermore, if prisoners believe their concerns are being dealt with quickly and satisfactorily, they will be less likely to perceive conditions of detention as unfair or discriminatory. This will, in turn, lower 348 tensions in the prison and improve staff-prisoner relations. Special procedures must be applied to deal with allegations of torture or other illtreatment of prisoners. They must be dealt with immediately and result in a prompt and impartial investigation, conducted by an independent national authority, whenever there are reasonable grounds to believe that an act of torture or other ill-treatment may have 349 been committed, irrespective of whether a complaint has been received. 346 UN Committee against Torture, “Concluding Observations on the Seventh Periodic Report of the Netherlands” op. cit., note 202, para. 28. 347 ODIHR & PRI, Guidance Document on the Nelson Mandela Rules, op. cit., note 10, Chapter 1, para. 134. 348 Ibid., Chapter 1, para. 131. 349 UN Nelson Mandela Rules, op. cit., note 13, Rule 57 (3); see also ODIHR & PRI, Guidance Document on the Nelson Mandela Rules, op. cit., note 10, Chapter 1, paras. 161-162 and Chapter 3, paras. 68-101. 71