alteration and elimination of evidence, the diligence with which the State must act in the investigation is increased. 780 500. In addition, both the Commission and the representatives alleged that no investigation had been conducted into other individuals who were possibly responsible. In this regard, it should be recalled that it is not for the Court to analyze the hypotheses concerning the perpetrators that arose during the investigation of the events and, consequently, to establish individual responsibilities; the definition of these is the purview of the domestic criminal courts. 781 However, it notes that, in complex cases such as this one, the obligation to investigate entails the duty to use the efforts of the State apparatus to clarify the structure that permitted these violations, the causes, the beneficiaries, and the consequences; hence an investigation can only be effective if it is conducted based on a comprehensive vision of the facts that takes into account the background and the context in which they occurred and that seeks to reveal the structures of participation. 782 In this regard, the Court notes that, following the initial accusations and charges brought by the Prosecution Service between 2007 and 2009 (supra paras. 174), no other person has been implicated in the investigations into these events, despite various judicial decisions issued at the domestic level establishing that other individuals who were possibly responsible should be investigated. 501. The Court underlines the opinion of expert witness Carlos Castresana in this regard: [The facts of the case were presumably] committed by authorities and agents who are sufficiently identified, belonging to known military and police units, who did not act on their own accord, but as part of a specific upward chain of command – the masterminds – and downward – perpetrators. It is unlikely that a mid-level military leader could have decided to retake the Palace of Justice, […] without the consent of his superiors. […] and, similarly, in all probability, the tasks of interrogating the detainees and their torture, the enforced disappearances, and the extrajudicial executions must have been perpetrated by subordinates. 783 502. The Court also emphasizes that, in the investigation of complex crimes, the design and implementation of an investigation strategy is essential in order to concentrate efforts and resources as effectively as possible. The Court observes and assesses positively that, between 2005 and 2010, the investigation that was conducted abided by this principle, as explained during the public hearing on the merits held in this case by the person who was the prosecutor in charge of the investigation. However, the Court notes that, after that stage, the investigations appear to have come to a halt, even though new investigations had been requested during the criminal proceedings that were held, and the need to obtain further evidence to achieve a definitive clarification of the events has been proposed. The Court stresses, in particular, that no information has been provided on any progress made in the investigations into what happened to Yolanda Santodomingo Albericci, Eduardo Matson Ospino, Orlando Quijano and José Vicente Rubiano Galvis, or into the disappearance and execution of Auxiliary Justice Carlos Horacio Urán Rojas. 503. The Court also emphasizes that, in January 2012, the Superior Court of Bogota exhorted the Prosecutor General’s Office to “create a special unit with exclusive 780 Cf. Expert opinion of Michael Reed provided by affidavit on November 6, 2013 (evidence file, folio 35641). 781 Cf. Case of Cantoral Huamaní and García Santa Cruz v. Peru. Preliminary objection, merits, reparations and costs. Judgment of July 10, 2007. Series C No. 167, para. 87, and Case of the Human Rights Defender et al. v. Guatemala. Preliminary objections, merits, reparations and costs. Judgment of August 28, 2014. Series C No. 283, para. 214. 782 Cf. Case of Manuel Cepeda Vargas v. Colombia. Preliminary objections, merits, reparations and costs. Judgment of May 26, 2010. Series C No. 213, para. 118, and Case of García and family members v. Guatemala. Merits, reparations and costs. Judgment of November 29, 2012. Series C No. 258, para. 148. 783 Expert opinion provided by affidavit by Carlos Castresana Fernández on November 6, 2013 (evidence file, folio 36274). 176