27 From Article 8 of the Convention it is evident that the victims of human rights violations, or their nextof-kin should have substantial possibilities to be heard and to act in the respective proceedings, both to clarify the facts and punish those responsible, and to seek due reparation.130 118. By the same token, the Court has ruled that the next of kin of the alleged victims have the right to expect, and the States the obligation to ensure, that what befell the alleged victims will be investigated effectively by the State authorities; that proceedings will be filed against those allegedly responsible for the unlawful acts; and, if applicable, the pertinent penalties will be imposed, and the losses suffered by the next of kin repaired.131 Based on the foregoing, once State authorities have knowledge of a violation of human rights, in particular of the rights to life, humane treatment, and personal liberty, 132 they should initiate a serious, impartial and effective investigation, ex officio and without delay,133 which should be carried out within a reasonable time.134 119. 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.135 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,136 and involving every State institution.137 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.138 120. In that connection, the duty to investigate, like the duty to prevent, is not breached merely because the investigation does not produce a satisfactory result. Nevertheless, it must be undertaken in a serious manner and not as a mere formality preordained to be ineffective,139 or as a step taken by private interests that depends upon the initiative of the victim or his family or upon their offer of proof. 140 130 I/A Court H.R., Case of García-Prieto et al. v. El Salvador. Preliminary Objections, Merits, Reparations and Costs. Judgment of November 20, 2007. Series C No. 168, par. 102; I/A Court H.R., The “Street Children” Case (Villagrán Morales et al.) v. Guatemala. Judgment of November 19, 1999. Series C No. 63, par. 227; and I/A Court H.R., Case of the Serrano-Cruz Sisters v. Guatemala. Merits, Reparations and Costs. Judgment of March 1, 2005. Series C No. 120, par. 63. 131 I/A Court H.R., Case of García-Prieto et al. v. El Salvador. Preliminary Objections, Merits, Reparations and Costs. Judgment of November 20, 2007. Series C No. 168, par. 103; I/A Court H.R., Case of Bulacio v. Argentina. Preliminary Objections, Merits, Reparations and Costs. Judgment of September 18, 2003. Series C No. 100, par. 114; and I/A Court H.R., Case of the Miguel Castro-Castro Prison v. Peru. Judgment of November 25, 2006. Series C No. 160, par. 382. 132 I/A Court H.R., Case of Cantoral-Huamaní and García-Santa Cruz v. Peru. Preliminary Objections, Merits, Reparations and Costs. Judgment of July 10, 2007. Series C No. 167, par. 100. 133 I/A Court H.R., Case of García-Prieto et al. v. El Salvador. Preliminary Objections, Merits, Reparations and Costs. Judgment of November 20, 2007. Series C No. 168, par. 101; I/A Court H.R., Case of the Gómez Paquiyauri Brothers v. Peru. Judgment of July 8, 2004. Series C No. 110, pars. 146; I/A Court H.R., Case of Cantoral-Huamaní and García-Santa Cruz v. Peru. Preliminary Objections, Merits, Reparations and Costs. Judgment of July 10, 2007. Series C No. 167, par. 130. 134 I/A Court H.R., Case of Bulacio v. Argentina. Judgment of September 18, 2003. Series C No. 100, par. 114; I/A Court H.R., Case of the Rochela Massacre v. Colombia. Judgment of May 11, 2007. Series C No. 163, par. 146; I/A Court H.R., Case of the Miguel Castro-Castro Prison v. Peru. Judgment of November 25, 2006. Series C No. 160, par. 382. 135 I/A Court H.R., Case of García-Prieto et al. v. El Salvador. Preliminary Objections, Merits, Reparations and Costs. Judgment of November 20, 2007. Series C No. 168, par. 101. 136 I/A Court H.R., Case of Bulacio v. Argentina. Judgment of September 18, 2003. Series C No. 100, par. 114; I/A Court H.R., Case of the Rochela Massacre v. Colombia. Judgment of May 11, 2007. Series C No. 163, par. 146; I/A Court H.R., Case of the Miguel Castro-Castro Prison v. Peru. Judgment of November 25, 2006. Series C No. 160, par. 382. 137 I/A Court H.R., Case of Cantoral-Huamaní and García-Santa Cruz v. Peru. Preliminary Objections, 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 v. Colombia. Judgment of January 31, 2006. Series C No. 140, par. 120; and I/A Court H.R., Case of Huilca Tecse v. Peru. Judgment of March 3, 2005. Series C No. 121, par. 66. 138 I/A Court H.R., Case of Zambrano-Vélez et al. v. Ecuador. Merits, Reparations and Costs. Judgment of July 4, 2007. Series C No. 166, par. 122. 139 I/A Court H.R., Velásquez Rodríguez Case. Honduras. Judgment of July 29, 1988. Series C No. 4, par. 177; I/A Court H.R., Case of Cantoral-Huamaní and García-Santa Cruz v. Peru. Preliminary Objections, Merits, Reparations and Costs. Judgment