186. As to the substance of the duty to investigate with due diligence, the Inter-American Court has held that the investigation should be undertaken utilizing all the legal means available and should be oriented toward the determination of the truth.233 In that same vein, the Court has found that the State has the duty to ensure that everything necessary is done to learn the truth about what happened and for those responsible to be punished,234 and involving every State institution.235 The Court has also said that the authorities should adopt all reasonable measures to guarantee the necessary probative material in order to carry out the investigation.236 187. Although the duty to investigate is one of means, not results, it must be assumed by the State as its own legal duty and be undertaken in a serious manner and not as a mere formality preordained to be ineffective,237 or simply as a step taken by private interests that depends upon the initiative of the victim or his family or upon their offer of proof.238 In that connection, with respect to due diligence in the analysis of the scene of a crime, the Inter-American Court and the Commission have taken into account the guidelines laid down in the United Nations Model Protocol for a Legal Investigation of Extralegal, Arbitrary and Summary Executions.239 188. Bearing the above parameters in mind, the Commission will determine in the instant case the State of Colombia carried out a serious and diligent investigation of the facts described in this report within a reasonable time. With that in mind, the Commission will analyze if each of the investigations was carried out with due diligence and in a reasonable time. Finally, the Commission will offer its conclusions on the international responsibility of the State. a. The failure to link and coordinate the investigations 189. The Commission notes that the investigations into the attack and subsequent death of Noel Emiro Omeara, the disappearance and execution of Guillermo Omeara Miraval, and the attack on Héctor Álvarez have been conducted separately in three different proceedings. The Commission has determined that in all three proceedings there are various statements and allegations made by family members on different occasions that identify the paramilitary group headed by Roberto Prada, as well as agents of the state, as those responsible for the crimes. Furthermore, the names of some of the alleged perpetrators, such as those with the aliases “El Ave” and “Rambo,” coincide in a number of inquiries. 190. The Commission observes that although the State has provided information, though not proof, regarding inspections of the records of the investigations, there continues to be a lack of analysis of the findings made in them and of investigative hypotheses that tie them all together. The Commission finds that the lack of linkage among the three investigations and the findings adopted in the framework of the “justice 233I/A Court H.R., Case of García-Prieto et al. Preliminary Objection, Merits, Reparations and Costs. Judgment of November 20, 2007, Series C No. Series C No. 168. par. 101. 234I/A Court H.R., Case of Bulacio. Judgment of September 18, 2003. Series C No. 100. par. 114; I/A Court H.R., Case of the Rochela Massacre. Judgment of May 11, 2007. Series C No. 163. par. 146; I/A Court H.R., Case of the Miguel Castro-Castro Prison. Judgment of November 25, 2006. Series C No. 160. par. 382. 235I/A Court H.R., Case of Cantoral-Huamaní and García-Santa Cruz. Preliminary Objection, Merits, Reparations and Costs. Judgment of July 10, 2007. Series C No. 167. par. 130; I/A Court H.R., Case of the Massacre of Pueblo Bello. Judgment of January 31, 2006. Series C No. 140. par. 120; and I/A Court H.R., Case of Huilca Tecse. Judgment March 3, 2005. Series C No. 121, par. 66. 236I/A Court H.R., Case of Zambrano-Vélez et al. Merits, Reparations and Costs. Judgment of July 4, 2007. Series C No. 166, par. 122. 237I/A Court H.R., Velásquez Rodríguez Case. Judgment of July 29, 1988. Series C No. 4. par. 177; I/A Court H.R., Case of Cantoral-Huamaní and García-Santa Cruz. Preliminary Objection, Merits, Reparations and Costs. Judgment of July 10, 2007. Series C No. 167. par. 131; and I/A Court H.R., Case of Zambrano-Vélez et al. Merits, Reparations and Costs. Judgment of July 4, 2007. Series C No. 166, par. 120. 238I/A Court H.R., Velásquez Rodríguez Case. Judgment of July 29, 1988. Series C No. 4. par. 177; I/A Court H.R., Case of Zambrano-Vélez et al. Merits, Reparations and Costs. Judgment of July 4, 2007. Series C No. 166, par. 120. 239The above instrument sets out a number of basic procedures: identification of the victim; recovery and preservation of evidentiary material related to the death to aid in any potential prosecution of those responsible; identification of possible witnesses and collection of statements from them concerning the death; determination of the cause, manner, location and time of death, as well as any pattern or practice that may have brought about the death; distinction between natural death, accidental death, suicide and homicide; identification and apprehension of the person(s) involved in the death; and bringing of the suspected perpetrator(s) before a competent court established by law. U.N. Doc E/ST/CSDHA/.12 (1991). The Commission has previously relied on United Nations documents to evaluate basic procedures to be carried out in such cases. See November 18, 2008. Report 10/95. Case 10.580, Ecuador. September 12, 1995, par. 53. 44