52 269. As the Court has indicated, to fulfill the duty to investigate with due diligence a violation of 300 the right to life, States are required to act assiduously, starting with the initial proceedings. In this regard, the Inter-American Court has taken into consideration the United Nations Manual on the Effective Prevention and Investigation of Extra-legal, Arbitrary and Summary Executions, specifying that “State authorities that conduct an investigation must, inter alia, a) identify the victim; b) recover and preserve the probative material related to the death, in order to facilitate any investigation; c) identify possible witnesses and obtain their statements in relation to the death under investigation; d) determine the cause, method, place and moment of the death, as well as any pattern or practice that could have caused the death; and e) distinguish between natural death, accidental death, suicide, and murder. In addition, it is essential to search exhaustively the scene of the crime and autopsies and analyses of human remains 301 must be carried out rigorously by competent professionals, using the most appropriate procedures.” 270. The Court has also stated that authorities must adopt reasonable methods to ensure the 302 collection of the evidence needed to conduct the investigation. 271. Regarding the importance of the actions taken by the authorities carrying out the initial steps in the investigation, the Court has held that due diligence “and criteria of independence and impartiality also extend to the non-judicial bodies responsible for the investigation prior to the judicial proceedings, conducted to determine the circumstances of a death and the existence of sufficient evidence. In the absence of these requirements, the State cannot subsequently exercise effectively and efficiently its authority to bring charges and the courts cannot conduct the judicial proceedings that this 303 type of violation calls for.” 272. In addition, and particularly important for this case, the Court has emphasized that The State’s obligation to carry out investigations with due diligence includes the obligation of all State authorities to collaborate in the gathering of evidence so that the objectives of an investigation may be achieved. The authority in charge of the investigation must ensure that all necessary investigate steps are undertaken and must take appropriate action, in accordance with domestic legislation, when this does not occur. At the same time, all other State authorities must collaborate with the examining judge and abstain from acts that obstruct the investigative 304 process. 273. Although the obligation is an obligation of means rather than results, it must be undertaken by the State as its own legal duty and not as a mere formality condemned in advance to be 300 I/A Court HR. Case of Zambrano Vélez et al. v. Ecuador. Merits, Reparations and Costs. Judgment of July 4, 2007. Series C, No. 166. para. 121. 301 I/A Court HR., Case of the Moiwana Community. Judgment of June 15, 2005. Series C, No. 124. para. 149; I/A Court HR., Miguel Castro Castro Prison Case. Judgment of November 25, 2006. Series C, No. 160. para. 383. Citing the United Nations Manual on the Effective Prevention and Investigation of Extra-legal, Arbitrary and Summary Executions, Doc. E/ST/CSDHA/.12 (1991). 302 I/A Court HR. Case of Zambrano Vélez et al. v. Ecuador. Merits, Reparations and Costs. Judgment of July 4, 2007. Series C, No. 166. para. 122. 303 I/A Court HR. Case of Cantoral Huamaní et García Santa Cruz v. Peru. Preliminary Objection, Merits, Reparations and Costs. Judgment of July 10, 2007. Series C, No. 167. para. 133. 304 I/A Court HR. Case of García Prieto et al. v. El Salvador. Preliminary Objection, Merits, Reparations and Costs. Judgment of November 20, 2007. Series C, No. 168. para. 112.