131 factors. However, in this case the complexity of the matter is also linked to the difficulties caused during the investigation, which originated in actions and omissions by the administrative and judicial authorities of the State itself, as will be analyzed in the following section. It is therefore not possible to sustain an argument to justify the duration of the investigations, as the State seeks to do, based on “vicissitudes and limitations in terms of financial and technical resources, […] as well as the critical public order situation in the areas where the investigations must be conducted and the evidence gathered.” 222. While it has been more than eight years since the facts took place, the criminal proceeding continues to be open and, despite the aforementioned delays, there have been certain results that must be taken into account. Therefore, the Court deems that, rather than basing its analysis on whether the term of the investigations has been reasonable, the responsibility of the State in light of Articles 8(1) and 25 of the Convention must be established by means of an assessment of the development and results of the criminal proceeding, that is, on the effectiveness of the duty to investigate the facts to establish the truth of what happened, to punish those responsible, and to provide reparation for the violations against the victims. * * * 223. As was pointed out, in cases of extra-legal executions, the jurisprudence of this Court is unequivocal: the State has the duty to begin ex officio, forthwith, a serious, impartial and effective investigation (supra para. 219) that must not be undertaken as a mere formality destined beforehand to be fruitless.259 224. In this regard, based on the United Nations Manual on the Effective Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions, this Court has specified the guiding principles that must be followed when a death may be due to an extra-legal execution. The State authorities in charge of an investigation must seek, at the least, inter alia: a) to identify the victim; b) to obtain and preserve evidence regarding the death, so as to aid any potential criminal investigation regarding those responsible; c) identify possible witnesses and receive their statements regarding the death under investigation; d) establish the cause, manner, place and time of death, as well as any pattern or practice that may have caused the death; and e) differentiate between natural death, accidental death, suicide, and homicide. It is also necessary to exhaustively investigate the crime scene, autopsies and analyses of human remains must be conducted rigorously, by competent professionals, applying the most appropriate procedures260 225. In the instant case, the investigation began almost immediately after the days of the massacre. It has been proven that the paramilitary remained in Mapiripán from July 15 to July 20, 1997, and the preliminary investigation of the facts was 259 See Case of the Moiwana Community, supra note 4, para. 146; Case of the Serrano Cruz Sisters, supra note, para. 61, and Case of Bulacio, supra note 196, para. 112. 260 See Case of the Moiwana Community, supra note 4, para. 149, and Case of Juan Humberto Sánchez, supra note 187, para. 127 and 132. Likewise, United Nations Manual on the Effective Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions, Doc. E/ST/CSDHA/.12 (1991).