international law, which are binding for States Parties, but also from domestic laws concerning the obligation to investigate ex officio certain illegal conducts and the norms that allow the victims or their next of kin to file complaints or lawsuits, evidence, petitions, or any other measure, in order to play a procedural role in the criminal investigation intended to establish the truth of the facts. 288 218. In light of this obligation, in the case of the investigation into the death of a person who was in State custody, as in this case, the corresponding authorities must initiate ex officio and without delay, a serious, impartial, and effective investigation. This investigation must be conducted using all available legal means to determine the truth and to investigate, prosecute and punish all those responsible for the facts, especially when State agents are or may be involved. 289 It should be noted that the duty to investigate is an obligation of means rather than results. Nevertheless, the Court reiterates that it must be assumed by the State as an inherent legal obligation and not as a mere formality preordained to be ineffective, or as a mere step take by private interests that depends upon the procedural initiative of the victims or their next of kin, or on the production of probative elements by private individuals. 290 219. The Court has established that the State, as guarantor of the rights recognized in the Convention, is responsible for respecting the rights to life and personal integrity of every individual in its custody. 291 In this regard, the State can be found responsible for the death of a person who has been in the custody of State agents when the authorities have not conducted a serious investigation into the facts followed by the prosecution of those responsible. 292 Thus, it is the State’s obligation to provide an immediate, satisfactory and convincing explanation of what happened to a person in its custody, and to disprove the allegations of its responsibility with appropriate probative elements. 293 A.2.2. Due diligence in the investigation of the death of Ricardo David Videla A.2.2.1. Lines of investigation 288 Cf. Case of Velásquez Rodríguez v. Honduras. Merits, para. 91, and Case of Vera Vera et al. v. Ecuador, para. 86. 289 Cf. Case of Velásquez Rodríguez v. Honduras. Merits, para. 177, and Case of Vera Vera et al. v. Ecuador, para. 87. 290 Cf. Case of Velásquez Rodríguez v. Honduras. Merits, para. 177, and Case of the Massacre of Santo Domingo v. Colombia, para. 157. 291 Cf. Case of Neira Alegría et al. v. Peru. Merits. Judgment of January 19, 1995. Series C No. 20, para. 60, and Case of Vera Vera et al. v. Ecuador, para. 88. 292 Cf. Case of Neira Alegría et al. v. Peru. Merits. Judgment of January 19, 1995. Series C No. 20, para. 60, and Case of Vera Vera et al. v. Ecuador, para. 88. 293 Cf. Case of Juan Humberto Sánchez v. Honduras, para. 111, and Case of Vera Vera et al. v. Ecuador, para. 88. It is worth mentioning the case law of the European Court of Human Rights on this matter, which has maintained that, under Article 3 of the European Convention, which recognizes the right to humane treatment, the State has the obligation to provide a “convincing explanation” for any injury suffered by a person deprived of his liberty. Also, based on reading Article 3 of the European Convention in conjunction with Article 1 of this instrument, it has stated that an effective official investigation is required when an individual makes a “credible assertion” that State agents have violated any of his rights stipulated in Article 3 of this instrument. The investigation must be able to achieve the identification and punishment of those responsible. Similarly, the European Court has stated that, to the contrary, the general prohibition of cruel, inhuman and degrading treatment, among others, would be “ineffective in practice,” because it would be possible for State agents to violate the rights of those in their custody with total impunity. Cf. ECHR. Case of Elci and Others v. Turkey (Nos. 23141 and 25091/94), judgment of 13 November 2003, paras. 648 and 649, and Case of Assenov and Others v. Bulgaria (No. 24760/94), judgment of 28 October 1999, para. 102. 72