244. However, the obligation to investigate, as a fundamental and conditioning element for the protection of certain violated rights, acquires a particular and determining importance and intensity in view of the severity of the crimes committed and the nature of the rights violated, 390 as in cases of grave human rights violations that occur as part of a systematic pattern or practice applied or tolerated by the State391 or in contexts of massive, systematic or generalized attacks on any sector of the population,392 because the urgent need to prevent the repetition of such events depends, to a great extent, on avoiding their impunity and meeting the expectations of the victims and society as a whole to know the truth about what happened.393 The elimination of impunity, by all legal means available, is fundamental for the eradication of extrajudicial executions, torture and other grave human rights violations.394 245. It has been proved and acknowledged by the State that the facts of the instant case refer, among other matters, to mass extrajudicial executions, acts of torture and of violence against women, as well as enforced displacement, committed in the context of the internal armed conflict in El Salvador and as part of a planned State policy against the civilian population living in areas associated with the guerrilla. 246. The Court notes that, under the American Convention, in force at the time of the massacre, the State had the obligation to investigate all the facts with due diligence, an obligation that remains in force. This obligation was reaffirmed by the State when depositing the instrument ratifying the Inter-American Convention to Prevent and Punish Torture on December 5, 1994, and subsequently, when depositing the instrument ratifying the Convention of Belém do Pará on January 26, 1996; therefore, the State should have ensured compliance with them as of those dates,395 even though they had not been adopted by the State when the massacres took place. 247. Owing to its importance, in the instant case the obligation to investigate cannot be fulfilled randomly, but must be conducted in keeping with the standards established by the international norms and case law that characterize investigations of grave human rights violations. This entails, first, creating an adequate domestic regulatory framework and/or organizing the system for the administration of justice in a way that its operation ensures that serious, impartial and effective investigations are conducted ex officio, without delay.396 248. The duty to investigate is an obligation of means and not of results that must be assumed by the State as its inherent legal duty and not as a simple formality preordained to be ineffective, or merely as a measure taken by private interests that depends on the procedural initiative of the victims, their next of kin, or the private submission of evidence.397 249. Similarly, this obligation entails the removal of all obstacles de jure and de facto that prevent the investigation and prosecution of the facts and, as appropriate, the punishment of all 390 Cf. Case of La Cantuta v. Peru. Merits, reparations and costs. Judgment of November 29, 2006. Series C No. 162, para. 110, and Case of González Medina and family members v. Dominican Republic. Preliminary objections, merits, reparations and costs. Judgment of February 27, 2012. Series C No. 240, para. 220. 391 Cf. Case of Goiburú et al. v. Paraguay. Merits, reparations and costs. Judgment of September 22, 2006. Series C No. 153, para. 82, and Case of Contreras et al. v. El Salvador, para. 127. 392 Cf. Case of Almonacid Arellano et al. v. Chile. Preliminary objections, merits, reparations and costs. Judgment of September 26, 2006. Series C No. 154, paras. 94 to 96 and 98 to 99, and Case of Manuel Cepeda Vargas v. Colombia, para. 42. 393 Cf. Case of Vargas Areco v. Paraguay, para. 81, and Case of Escué Zapata v. Colombia, para. 75. 394 Cf. Case of Vargas Areco v. Paraguay, para. 81, and Case of Escué Zapata v. Colombia, para. 75. 395 Cf. Case of the Miguel Castro Castro Prison v. Peru, para. 377, and Case of the Las Dos Erres Massacre v. Guatemala, para. 137. 396 Cf. Case of Velásquez Rodríguez v. Honduras. Merits, para. 110, and Case of Manuel Cepeda Vargas v. Colombia, para. 117. 397 Cf. Case of Velásquez Rodríguez v. Honduras. Merits, para. 177, and Case of Pacheco Teruel et al. v. Honduras. Merits, reparations and costs. Judgment of April 27, 2012. Series C No. 241, para. 129.. 81