25 violating Article 24 of the American Convention, invoking the categories expressly mentioned in Article 1(1) has certain effects.94 96. Now, as the Inter-American Court has stated, not every difference in treatment is discriminatory. The Court has differentiated between “distinctions” and “discriminations” such that the first constitute differences compatible with the American Convention as they are “reasonable and objective,” whereas the second constitute arbitrary differences that redound to the detriment of human rights.95 97. Bearing in mind that the evaluation of whether a distinction is “reasonable and objective” is done on a case-by-case basis, the Commission, the Court, and other international tribunals and organs have turned to the use of a scaled proportionality test that includes the following elements of analysis: (i) the existence of a legitimate aim; (ii) its suitability, that is, the determination of whether there is a logical relationship of causality from means to end as between the distinction and the end pursued; (iii) the existence of less restrictive and equally suitable alternatives; and (iv) proportionality in the strict sense, that is, the balance of the interests at stake and the degree of sacrifice of one with respect to the other.96 98. When distinctions are based on certain categories expressly mentioned in the nondiscrimination clauses of international human rights treaties there is a consensus that the analysis that is used to measure the reasonableness of the difference in treatment is especially strict. This is because, by their nature, such categories are considered “suspect” and therefore it is presumed that the distinction is incompatible with the American Convention. In that regard, only “overriding or urgent” considerations that must be analyzed in detail may be invoked as a justification.97 This strict analysis is precisely the guarantee that the distinction is not based on prejudices and/or stereotypes that generally surround suspect categories of distinctions.98 99. In practical terms this means that after having presented a distinction of this nature, the burden of proof is on the state and the general criteria referred to are evaluated carefully such that it is not sufficient for a state to argue the existence of a legitimate end, but the objective pursued with the 94 IACHR, Application to the Inter-American Court of Human Rights, Karen Atala and daughters, September 17, 2010, para. 78. 95 I/A Court H.R. Case of Castañeda Gutman v. Mexico. Preliminary Objections, Merits, Reparations and Costs. Judgment of August 6, 2008. Series C No. 184, para. 211; I/A Court H.R. Legal Status and Rights of Undocumented Migrants, Advisory Opinion OC-18/03, September 17, 2003, Series A. No. 18, para. 84. 96 IACHR, Application to the Inter-American Court of Human Rights, Karen Atala and daughters, September 17, 2010, para. 86. 97 IACHR, Access to Justice for Women Victims of Violence in the Americas, OEA/Ser. L/V/II. doc. 68, January 20, 2007, paras. 80 and 83; IACHR, Report on Terrorism and Human Rights, OEA/Ser.L/V/ll.116 Doc. 5 rev. 1 corr., October 22, 2002, para. 338; IACHR, Report No. 4/01, Case 11.625, María Eugenia Morales de Sierra (Guatemala), January 19, 2001, para. 36; IACHR, Annual Report 1999, Considerations regarding the compatibility of affirmative action measures designed to promote the political participation of women with the principles of equality and non-discrimination, chapter VI; IACHR, Report No. 38/96, Case 10.056, X and Y (Argentina), October 15, 1996, paras. 73 and 74. In this report the Commission characterized the aim pursued as an “absolute necessity.” 98 para. 88. IACHR, Application to the Inter-American Court of Human Rights, Karen Atala and daughters, September 17, 2010,