(a) must be exceptional and must be planned, and limited proportionately by the authorities. In this regard, coercive measures or force can only be used once all other means of control have been exhausted and have failed; (b) as a general rule, the use of firearms and lethal force against the individual must be prohibited, and the exceptional use must be established by law and be interpreted restrictively, so that it is only that which is “absolutely necessary” in relation to the force or threat to be prevented; (c) it must be limited by the principles of proportionality, necessity and humanity. Thus, excessive or disproportionate use of force by law enforcement officials that results in loss of life may amount to arbitrary deprivation of life, and (d) domestic law must establish standards for the use of lethal force and firearms by State agents that are sufficiently clear, as well as to ensure independent control of its legality. The obligation to open a serious, independent, impartial and effective investigation when security agents are known to have used firearms with lethal consequences constitutes a fundamental and determinant element for the protection of the right to life which has been annulled in such situations.45 50. The American Convention also expressly recognizes the right to personal integrity, a legal right whose protection includes the main purpose of the absolute prohibition of torture and cruel, inhuman or degrading punishment or treatment.46 In its case law, this Court has considered that the said prohibition belongs today to the domain of ius cogens.47 The right to personal integrity cannot be suspended under any circumstance.48 51. Thus, an international juridical system has been established for the absolute prohibition of all forms of torture, both physical and mental; and, regarding the latter, it has been recognized that threats and the real danger that an individual may be subjected to serious physical injury can produce, in certain circumstances, moral anguish of such a degree that it can be considered “mental torture.”49 52. The Court has already established that “[t]he violation of the right to physical and mental integrity of the individual is a type of violation that has several levels ranging from torture to other types of humiliation or cruel, inhuman or degrading treatment, the physical and mental aftereffects of which vary in intensity according to endogenous and exogenous factors that must be established in each specific situation.”50 In other words, the personal characteristics of an alleged victim of torture or cruel, inhuman or degrading treatment must be taken into account when determining whether their personal integrity has been violated and, consequently, the suffering and the sense of humiliation is increased when the 45 Cf. Case of Zambrano Vélez et al. v. Ecuador. Merits, reparations and costs. Judgment of July 4, 2007. Series C No. 166, paras. 81, 83, 84, 86 and 88. Also, cf. Case of Montero Aranguren et al. (Retén de Catia) v. Venezuela. Preliminary objection, merits, reparations and costs. Judgment of July 5, 2006. Series C No. 150, paras. 66, 67, 68 and 75. 46 Cf. Case of Ximenes Lopes v. Brazil. Merits, reparations and costs. Judgment of July 4, 2006. Series C No. 149, para. 126, and Case of Torres Millacura et al., supra note 41, para. 84. 47 Cf. Case of Cantoral Benavides v. Peru. Merits. Judgment of August 18, 2000. Series C No. 69, para. 95, and Case of Torres Millacura et al., supra note 41, para. 84. 48 Cf. Case of the “Children’s Rehabilitation Institute” v. Paraguay. Preliminary objections, merits, reparations and costs. Judgment of September 2, 2004. Series C No. 112, para. 157, and Case of Torres Millacura et al., supra note 41, para. 84. 49 Cf. Case of Cantoral Benavides, supra note 47, para. 102, and Case of Torres Millacura et al., supra note 41, para. 85. 50 Case of Loayza Tamayo, supra note 20, para. 57, and Case of Torres Millacura et al. supra note 41, para. 86. 21