71 a mere formality condemned in advance to be fruitless.362 In that regard, the investigation must be conducted with due diligence, effectively, seriously and impartially,363 and within a reasonable period of time.364 Because of this the presence of acts obstructing justice, impediments or problems involving the authorities’ unwillingness to collaborate that prevented or are preventing clarification of the case constitutes a violation of the right to a fair trial. The IACHR also draws attention to the fact that the obligation to investigate and punish all incidents involving the violation of rights protected by the Convention requires punishing not only the material perpetrators of the incidents violating human rights, but also the intellectual authors of said violations.365 244. The Commission, as the Court has done in the cases against Colombia that have already been mentioned, cannot but draw attention to the fact that the events of the present case are part of a situation where there is a high rate of impunity for crimes perpetrated by paramilitary groups.366 Regarding this, the Court has contended that the actions of the paramilitary groups have not found in the judiciary an adequate and faithful response to the international commitments made by the State, which led to the establishment of fertile ground for these groups to operate on the fringes of the law and to commit acts as those in the present case.367 In the Case of Cepeda Vargas v. Colombia, the Court stated that the right to a fair trial and judicial protection had been violated because "the absence of a thorough investigation fosters the impunity of severe violations of human rights perpetrated jointly by members of paramilitary groups and law enforcement agents.”368 245. In that regard, bearing in mind the above-mentioned precedents that establish that the State’s obligations to investigate in this type of case are all the more pressing, due to a joint action between the army and a paramilitary group,369 the Commission shall examine whether, in the present case, the State of Colombia conducted a sound and diligent investigation within a reasonable period of time: Regarding this, the IACHR shall rule on the various domestic proceedings that were filed and processed in the State of Colombia. 362 I/A Court H.R., Case of Velásquez Rodríguez v. Honduras. Merits. Judgment of July 29, 1988. Series C No. 4, paragraph 177; I/A Court H.R., Case of Cantoral Huamaní and García Santa Cruz v. Peru. Preliminary Objection, Merits, Reparations and Costs. Judgment of July 10, 2007. Series C No. 167, paragraph 131. 363 I/A Court H.R., Case of García Prieto and others v. El Salvador. Preliminary Objection, Merits, Reparations and Costs. Judgment of November 20, 2007. Series C No. 168, paragraph 101; Case of the Gómez Paquiyauri Brothers v. Peru. Judgment of July 8, 2004. Series C No. 110, paragraph 146; I/A Court H.R., Case of Cantoral Huamaní and García Santa Cruz v. Peru. Preliminary Objection, Merits, Reparations and Costs. Judgment of July 10, 2007. Series C No. 167, paragraph 130. 364 I/A Court H.R., Case of Bulacio v. Argentina. Judgment of September 18, 2003. Series C No. 100, paragraph 114; I/A Court H.R., Case of the Rochela Massacre v. Colombia. Merits, Reparations and Costs. Judgment of May 11, 2007. Series C. No. 163, paragraph 146; I/A Court H.R., Case of the Penal Miguel Castro Castro v. Peru. Judgment of November 25, 2006. Series C No. 160, paragraph 382. 365 IACHR, Report on the Situation of Human Rights Defenders in the Americas, OEA/Ser.L/V/II.124. Doc. 5 rev.1, March 7, 2006, paragraph 109. 366 I/A Court H.R., Case of the Pueblo Bello Massacre v. Colombia. Merits, Reparations and Costs. Judgment of January 31, 2006. Series C No. 140. paragraph 149. 367 I/A Court H.R., Case of the Pueblo Bello Massacre v. Colombia. Merits, Reparations and Costs. Judgment of January 31, 2006. Series C No. 140. paragraph 149. 368 I/A Court H.R., Case of Cepeda Vargas v. Colombia. Preliminary Objections, Merits, Reparations and Costs. Judgment of May 26, 2010. Series C No. 213, paragraph 215. 369 I/A Court H.R., Case of the Pueblo Bello Massacre. Merits, Reparations and Costs. Judgment of January 31, 2006. Series C No. 140, paragraph 126.