61 This is a fair expectation that the State must satisfy,264 on the one hand by the obligation to investigate human rights violations and, on the other, by the public dissemination of the results of the criminal and investigative proceedings.265 To guarantee the right to information and to know the truth, the government authorities must act in good faith and carry out diligently the actions required to ensure the effectiveness of that right, especially as this refers to knowing the truth of what happened in cases of grave human rights violations such as the forced disappearances in this case.266 171. In this regard, the Court considers that the State authorities are obliged to collaborate in the collection of evidence to achieve the goals of the investigation, and to abstain from actions that represent obstructions to the progress of the investigative process.267 In the same way, it is essential that the bodies in charge of the investigations be endowed, formally and substantially, with the adequate and necessary powers and guarantees to access the documentation and information that is pertinent for investigating the facts denounced and obtaining indications or evidence of the whereabouts of the victims.268 Furthermore, it is crucial that the authorities in charge of the investigation have full access to the documentation in the State’s possession as well as to places of detention.269 The State cannot shield itself behind the lack of evidence of the existence of the requested documents, but, on the contrary, it must justify the refusal to provide them, demonstrating that it has taken all available measures to prove that the requested information does not exist.270 In this regard, in the case of human rights violations, the Court has indicated that “the State authorities cannot shield themselves behind mechanisms such as State secrets or the confidentiality of the information, or by reasons of public interest or national security, to fail to provide the information required by the judicial or administrative authorities in charge of the pending investigations or proceedings.”271 172. Regarding the effectiveness of the Law on Access to Public Information in El Salvador, since it was not applied in this case, the Court does not find it necessary to analyze it, because the purpose of the Court’s contentious jurisdiction is not to review domestic legislation in the abstract.272 264 Cf. Case of Velásquez Rodríguez, supra note 23, para. 181; Case the Dos Erres Massacre, supra note 150, para. 149, and Case of Anzualdo Castro, supra note 109, para. 119. 265 Cf. Case of Las Palmeras v. Colombia. reparations and costs. Judgment of November 26, 2002. Series C No. 96; Case the Dos Erres Massacre, supra note 150, para. 149, and Case of Anzualdo Castro, supra note 109, para. 119. 266 Cf. Case of Gomes Lund et al. (Guerrilha do Araguaia), supra note 97, para. 211. 267 Cf. Case of García Prieto et al. v. El Salvador. Preliminary objections, merits, reparations and costs. Judgment of November 20, 2007. Series C No. 168 para. 112, and Case the Dos Erres Massacre, supra note 150, para. 144. 268 Cf. Case of Tiu Tojín, supra note 18, para. 77; Case of Ibsen Cárdenas and Ibsen Peña, supra note 100, para. 168 and Case of Radilla Pacheco, supra note 25, para. 222. 269 Cf. Case of Anzualdo Castro, supra note 109, para. 135, citing the Case of Myrna Mack Chang v. Guatemala. Merits, reparations and costs. Judgment of November 25, 2003. Series C No. 101, paras. 180 to 182; Case of Tiu Tojín, supra note 18, para. 77, and Case of La Cantuta, supra note 184, para. 111. See also Article X of the Inter-American Convention on the Forced Disappearance of Persons, and Article 12 of the International Convention for the Protection of All Persons from Enforced Disappearance. 270 Cf. Case of Gomes Lund et al. (Guerrilha do Araguaia), supra note 97, para. 211. 271 Case of Myrna Mack Chang, supra note 269; Case of Gomes Lund et al. (Guerrilha do Araguaia), supra note 97, para. 202, and Case of Tiu Tojín, supra note 18, para. 77. 272 Cf. Case of Genie Lacayo v. Nicaragua. Preliminary objections. Judgment of January 27, 1995. Series C No. 21, para. 50; Case of Cabrera García and Montiel Flores v. Mexico. Preliminary objection, merits, reparations and