- 13 - Commission has autonomy and independence in the exercise of its mandate as established by the American Convention and, particularly, in the exercise of its functions in the processing of individual petitions.25 Also, in matters that the Court is examining, the Court has the authority to control the legality of the Commission’s actions,26 which does not necessarily entail reviewing the proceedings conducted before the latter, aside from in exceptional cases in which there has been a serious error that violates the parties’ right to defense.27 Hence, the party that affirms the existence of a serious error must prove it;28 consequently, a complaint or difference of opinion in relation to the actions of the Commission is not sufficient.29 32. In the instant case, the Court observes that, during the proceedings before the Commission, the State acknowledged “in good faith, that the case of [Senator] Cepeda was a different and independent case,” even when the Commission indicated that it would proceed to the merits stage30 and considered the admissibility procedure exhausted. Nevertheless, it is true that the State alleged that it accepted the severance of the case provided that “limitations were placed on the factual framework, the purpose of the dispute, and the burden of proof on the two parties.” Following the severance and at the public hearing held in March 2007, the Commission considered that the admissibility procedure had concluded and did not distinguish specific facts in Admissibility Report No. 5/97 applicable to the Cepeda Vargas case. However, according to the Commission, “the State indicated on at least two occasions while the case was being processed (at the public hearing […] before the Commission and [in the] brief of October 23, 2007), its understanding that the Cepeda case was at the merits stage, which logically implied that the discussion on admissibility had concluded with Report No. 5/97.” Also, during the merits stage before the Commission, the State had three opportunities to submit observations on the representatives’ arguments, and was even granted three extensions.31 25 Cf. Control of Legality in the Exercise of the Powers of the Inter-American Commission on Human Rights (Arts. 41 and 44 of the American Convention on Human Rights). Advisory Opinion OC-19/05 of November 28, 2005. Series A No. 19, first operative paragraph; Garibaldi v. Brazil. Preliminary objections, merits, reparations and costs. Judgment of September 23, 2009. Series C No. 203, para. 35, and Case of Escher et al. v. Brazil. Preliminary objections, merits, reparations and costs. Judgment of July 6, 2009. Series C No. 200, para. 22. 26 Cf. Control of Legality in the Exercise of the Powers of the Inter-American Commission on Human Rights (Arts. 41 and 44 of the American Convention on Human Rights). Advisory Opinion OC-19/05, supra note 25, third operative paragraph; Case of Garibaldi v. Brazil, supra note 25, para. 35, and Case of Escher et al. v. Brazil, supra note 25, para. 22. 27 Cf. Dismissed Congressional Employees (Aguado Alfaro et al.) v. Peru. Preliminary objections, merits, reparations and costs. Judgment of November 24, 2006. Series C No. 158, para. 66; Case of Garibaldi v. Brazil. Preliminary objections, supra note 25, para. 35, and Case of Escher et al. v. Brazil, supra note 25, para. 22. 28 Cf. Case of Dismissed Congressional Employees (Aguado Alfaro et al.) v. Peru, supra note 27, para. 66; Case of Escher et al. v. Brazil, supra note 25, para. 23, and Castañeda Gutman v. United Mexican States. Preliminary objections, merits, reparations and costs. Judgment of August 6, 2008. Series C No. 184, para. 42. 29 Cf. Saramaka People v. Suriname. Preliminary objections, merits, reparations and costs. Judgment of November 28, 2007. Series C No. 172, para. 32; Case of Escher et al. v. Brazil, supra note 25, para. 23, and Case of Dismissed Congressional Employees (Aguado Alfaro et al.) v. Peru, supra note 27, para. 66. 30 The Commission informed the State that, “in view of the new procedural stage of the case, it needed to ask the Government of the Republic of Colombia to submit its observations on case No. 12,531 within two months […]”. Cf. note sent by the Inter-American Commission on November 28, 2005 (evidence file, tome III, appendix III to the application, folio 1002). 31 The State submitted observations during the merits proceedings on February 28, 2007, October 23, 2007 and May 30, 2008 (evidence file, tomes I and II, appendix III to the application, folios 293 to 304, 653 to 697 and 828 to 840). It requested extensions on March 21, 2006, June 27, 2007, and April 8, 2008, all of which were granted by the Commission (evidence file, tomes I and II, appendix III to the application, folios 323 to 325, 695 to 697 and 881).