66 this regard, the first stages of the investigation can be especially crucial in cases of the gender-based murder of a woman, because any errors that occur in procedures such as the autopsy and the collection and preservation of physical evidence can result in preventing or obstructing the possibility of proving relevant aspects such as sexual violence. With regard to the autopsies performed in a case of gender-based murder, the Court has stipulated that the genitalia should be examined carefully for signs of sexual abuse, and oral, vaginal and rectal fluids should be preserved, as well as foreign hairs and the pubic hair of the victim.272 Also, in cases where acts of violence against women are suspected, the criminal investigation should include a gender perspective and be carried out by officials with training in similar cases and in attending to victims of discrimination and gender-based violence.273 189. In addition, the Court indicates that, pursuant to Article 2 of the American Convention and Article 7(c) of the Convention of Belém do Pará, States have the obligation to adopt laws or implement the necessary measures to allow the authorities to investigate with due diligence in cases where violence against women is suspected.274 190. In this section, the Court will examine the following aspects: B.1) Irregularities following the discovery of the body of María Isabel, and subsequent actions of State officials (preservation of the crime scene, site inspection, removal of the body, chain of custody of the evidence, autopsy, and expert appraisals); B.2) Tracing of telephone calls; B.3) Failure to adopt precautionary measures for a suspect; B.4) Discrimination and absence of genderbased investigation, and B.5) Reasonable time. B.1) Irregularities following the discovery of the body of María Isabel, and subsequent actions of State officials (preservation of the crime scene, site inspection, removal of the body, chain of custody of the evidence, autopsy and expert appraisals) 191. On other occasions this Court has established that the proficient determination of the truth, in accordance with the obligation to investigate a death, must be demonstrated meticulously starting with the very first procedures. 275 Thus, the Court has described the guiding principles that must be observed in an investigation into a violent death. The State authorities who conduct an investigation of this type should try, at least to: (i) identify the victim; (ii) recover and preserve the probative elements related to the death in order to assist any potential criminal investigation of those responsible; (iii) identify possible witnesses and obtain their statements concerning the death investigated; (iv) determine the cause, manner, place and time of death, as well as any pattern or practice that may have resulted in the death, and (v) distinguish between natural or accidental death, suicide and murder. It is also necessary to carry out a thorough investigation of the scene of the crime, and rigorous autopsies and analyses of human remains must be performed by competent professionals, using the most appropriate procedures. 276 The Court has established that the 272 Cf. Case of González et al. (“Cotton Field”), supra, para. 310, and United Nations Manual on the Effective Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions - Model Protocol for a Legal Investigation of Extra-legal, Arbitrary and Summary Executions (Minnesota Protocol), UN Doc. E/ST/CSDHA/.12 (1991). 273 Cf. Case of González et al. (“Cotton Field”), supra, para. 455. 274 Cf. Case of González et al. (“Cotton Field”), supra, para. 388. This can be done by standardizing the protocols, manuals, and expert and justice services, used to investigate any crime related to the disappearance, sexual violence or murder of women, in keeping with the Istanbul Protocol, the United Nations Model Protocol for a Legal Investigation of Extra-legal, Arbitrary and Summary Executions, and international standards for searching for missing persons, based on a gender perspective. 275 Cf. Case of Servellón García et al. v. Honduras. Merits, reparations and costs. Judgment of September 21, 2006. Series C No. 152, para. 120; Case of González et al. (“Cotton Field”), supra, para. 300, and Case of Luna López, supra, para. 159. 276 Cf. Case of Juan Humberto Sánchez v. Honduras. Preliminary objection, merits, reparations and costs. Judgment of June 7, 2003. Series C No. 99, para. 127; Case of González et al. (“Cotton Field”), supra, para. 300, and Case of Luna López, supra, footnote 256.