65 victims or their next of kin to file complaints or submit claims, evidence or petitions or take any other step in order to play a procedural role in the criminal investigation to establish the truth of the events.263 185. The Court recalls that, in cases of violence against women, the general obligations established in Articles 8 and 25 of the American Convention are supplemented and enhanced for those States that are a party to it by the obligations arising from the specific inter-American treaty, the Convention of Belém do Pará.264 Article 7(b) of this Convention specifically obliges the States parties to use due diligence to prevent, punish and eradicate violence against women.265 Article 7(c) of the Convention of Belém do Pará obliges the States parties to adopt the necessary laws to investigate and punish violence against women.266 In such cases, the State authorities should open a genuine, impartial and effective investigation ex officio as soon as they are made aware of acts that constitute violence against women, including sexual violence. 267 Thus, in the case of an act of violence against a woman, it is particularly important that the authorities in charge of the investigation conduct it in a determined and effective manner, taking into account society’s duty to reject violence against women and the State’s obligation to eradicate this and to ensure that victims have confidence in the State institutions established to protect them. 268 186. The Court has also indicated that the duty to investigate has additional implications in the case of women who are killed or suffer ill-treatment or constraint of their personal liberty within the framework of a general context of violence against women. 269 187. This standard is wholly applicable when analyzing the scope of the obligation of due diligence in the investigation of cases of gender-based violence.270 In practice, it is often difficult to prove that a murder or act of violent aggression against a woman is genderbased. At times this impossibility stems from the absence of a thorough and effective investigation of the violent incident and its causes by the authorities. This is why the State authorities are bound to investigate ex officio the possible gender-based discriminatory connotations of an act of violence perpetrated against a woman, especially when there are specific indications of sexual violence or some type of evidence of cruelty towards the body of the woman (for example, mutilations), or when such an act takes place in a context of violence against women in a specific country or region. 188. Furthermore, the Court has established that, in cases when gender-based murder is suspected, the State’s obligation to investigate with due diligence includes the duty to order, ex officio, the pertinent expert appraisals and examinations aimed at verifying whether the murder was sexually motivated or whether some kind of sexual violence occurred. Thus, the investigation into a supposed gender-based murder should not be limited to the death of the victim, but should include other specific violations of personal integrity such as torture and acts of sexual violence. In a criminal investigation into sexual violence, the investigative procedures must be coordinated and documented, and the evidence handled diligently, taking sufficient samples, performing tests to determine the possible authors of the act, obtaining other evidence such as the victim’s clothes, the immediate inspection of the crime scene, and ensuring the correct chain of custody. 271 In 263 Cf. Case of García Prieto et al., supra, para. 104, and Case of Mendoza et al., supra, para. 217. 264 Cf. Case of Fernández Ortega et al., supra, para. 193, and Case of the Massacres of El Mozote and nearby places, supra, para. 243. 265 Cf. Case of Fernández Ortega et al., supra, para. 193, and Case of J., supra, para. 350. 266 Cf. Case of the Miguel Castro Castro Prison, supra, para. 344, and Case of González et al. (“Cotton Field”), supra, para. 287. 267 Cf. Case of the Miguel Castro Castro Prison, supra, para. 378, and Case of J., supra, para. 342. 268 Cf. Case of Fernández Ortega et al., supra, para. 193, and Case of J., supra, para. 342. 269 Cf. Case of González et al. (“Cotton Field”), supra, para. 293. 270 Cf. Case of González et al. (“Cotton Field”), supra, para. 293. 271 Cf. Case of Fernández Ortega et al., supra, para. 194, and Case of J., supra, para. 344.