5 regarding the murders exclusively[, but] it is necessary to refocus on the overall matter of the instant case and the denial of justice”. 16. That as regards to the observations made by the State regarding the lack of provisions on the res judicata principle in the legislation of Guatemala, the Commission found that “the Court has already dealt with this matter in the Judgment upon ordering the performance of investigations, determination, prosecution and punishment of those responsible, and also the adoption of the domestic measures necessary to render these obligations effective”. 17. That in cases of extra-judicial executions, it is essential that the States conduct an effective investigation into any deprivation of the right to life enshrined in Article 4 of the Convention, and to punish those responsible, particularly when State agents are involved.6 As regards the obligation to guarantee the right set forth in Article 5 of the American Convention, the Court has indicated that said obligation comprises the State’s duty to investigate possible acts of torture or other cruel, inhuman or degrading treatment.7 18. That the duty to investigate constitutes an unavoidable obligation of the State resulting from international law and, as mentioned by this Court, in the case of serious violation of fundamental rights, the need to prevent the repetition of those events depend, largely, on successful avoidance of impunity and satisfaction of the expectations of the victims and society as a whole to finally know the truth about the events.8 19. That the Court has defined impunity as the overall failure to investigate, arrest, prosecute and convict those responsible for violations of the rights protected under the American Convention.9 20. That impunity may arise in different manners; as a result of the State's failure to organize the mechanisms necessary to investigate a crime10 or of carrying out domestic proceedings that result in delays and undue hindrances;11 of failing to formally define an autonomous crime (e.g. crime of forced disappearance), which prevents the adequate performance of criminal proceedings;12 of adopting self-amnesty laws;13 of failing to enforce 6 Cf. Case of Myrna Mack Chang v. Guatemala. Merits, reparations and costs. Judgment of November 25, 2003. Series C No. 101, para. 156; and Case of Valle-Jaramillo et al. v. Colombia. Merits, reparations and costs. Judgment of November 27, 2008. Series C No. 192, para. 101. 7 Cf. Case of the Moiwana Community v. Suriname. Preliminary Objections, Merits, Reparations and Costs. Judgment of June 15, 2005. Series C No. 124, para. 92; Case of the Miguel Castro-Castro Prison v. Perú. Merits, Reparations and Costs. Judgment of November 25, 2006. Series C No. 160, para. 344; and Case of Bueno Alves v. Argentina. Merits, reparations and costs. Judgment of May 11, 2007. Series C No. 164, para. 88. 8 Cf. Case of Vargas-Areco v. Paraguay. Merits, reparations and costs. Judgment of September 26, 2006. Series C No. 155, para. 81; Case of the Miguel Castro-Castro Prison v. Perú, supra note 7, para. 347; and Case of Bueno Alves v. Argentina, supra note 7, para. 90. 9 Cf. Case of the “White Van” (Paniagua Morales et al.) v. Guatemala. Merits. Judgment of March 8, 1998. Series C No. 37, para. 173; Case of Vargas-Areco v. Paraguay, supra note 8, para. 153; and Case of Tiu Tojín v. Guatemala. Merits, reparations and costs. Judgment of November 25, 2008. Series C. No. 190, para. 69. 10 Cf. Case of Velásquez-Rodríguez v. Honduras, Merits. Judgment of July 29, 1988. Series C No. 4, para. 176 and 177; Case of Heliodoro Portugal v. Panamá. Mertis, reparations and costs. Judgment of August 12, 2008. Series C No. 186, para. 116; and Case of Tiu Tojín v. Guatemala, supra note 9, para. 69. 11 Cf. Case of Bulacio v. Argentina. Merits, reparations and costs. Judgment of September 18, 2003. Series C No. 100, para. 115; Case of Servellón García et al. v. Honduras. Mertis, reparations and costs. Judgment of September 21, 2006. Series C No. 152, para. 151; and Case of Bayarri v. Argentina. Preliminary Objections, Merits, Reparations and Costs. Judgment of October 30, 2008. Series C No. 187, para. 116. 12 Cf. Case of Heliodoro-Portugal v. Panamá, supra note 10, para. 183. 13 Cf. Case of Barrios Altos v. Perú. Judgment of March 14, 2001. Series C No. 75, para. 43.