63 B. Considerations of the Court 178. The Court has already determined that, even though it cannot be asserted that every murder of a woman that occurred at the time of the events was gender-based, it is probable that this was true of María Isabel’s murder based on how the girl’s body was found. Indeed, it has been said that women victims of gender-based murder frequently show signs of cruelty during the violence perpetrated against them, as well as signs of sexual abuse or mutilation (supra para. 78). In line with these characteristics, María Isabel’s body was found with clear signs of violence, including signs of strangulation, a wound to the head, a cut on one ear and bites on her upper arms; her head was covered by towels and a plastic bag, and she had food in her mouth and nose (supra para. 99); in addition, the bottom part of her blouse and underpants were torn (supra para. 110). This is relevant and sufficient for applying Article 7 of the Convention of Belém do Pará to the case.254 It should be noted that the lack of absolute certainty in this regard is a result of the failure to complete the domestic investigation, as well as the way in which, to date, this has been conducted. Thus, for example, significant elements, such as the presence of sexual violence in the incident, has not been determined with certainty (supra para. 111 and infra para. 196.b). 179. The Court also finds it relevant to recall its case law with regard to the criteria applicable to the assessment of the evidence in a case. Since its first contentious case, this Court has indicated that, for an international court, the criteria for assessment of evidence are less strict that under domestic legal systems, and has maintained that it may assess the evidence unreservedly. The Court must assess the evidence in a way that takes into account the significance of attributing international responsibility to a State and that, despite this, is able to establish conviction about the truth of the alleged facts.255 180. With regard to the alleged impediments to the correct implementation of certain procedures at the time of the events (supra para. 171), the Court recalls that it is a basic principle of international law, supported by international jurisprudence, that States are bound to observe their treaty-based obligations in good faith (pacta sunt servanda) and, as this Court has already indicated and as established in Article 27 of the 1969 Vienna Convention on the Law of Treaties, States may not invoke the provisions of their internal law as justification for failure to do so.256 Hence, the State cannot excuse failure to comply with its obligation to investigate with the due diligence by affirming that, at the time of the events, there were no laws, procedures or measures for conducting the initial investigative measures properly in keeping with the standards of international law that are evident in the applicable treaties in force at the time of the events, and that this Court has indicated in its case law (infra para. 188 and 189). Nevertheless, the Court has noted that Guatemala has 254 Article 1 of the Convention of Belém do Pará defines violence against women as “any act or conduct, based on gender, which causes death or physical, sexual or psychological harm or suffering to women, whether in the public or the private sphere.” The Court has stated that “CEDAW […] has indicated that ‘[v]iolence against women is a form of discrimination that creates a significant impediment to their enjoyment of rights and freedoms on an equal footing with men.” Case of González et al. (“Cotton Field”), supra, paras. 143, 401 and 395. Furthermore, the Court has also indicated that “not every violation of a human right committed against a woman necessarily results in a violation of the provisions of the Convention of Belém do Pará.” Case of Ríos et al. v. Venezuela. Preliminary objections, merits, reparations and costs. Judgment of January 28, 2009. Series C No. 194, para. 279. This does not mean that, in relation to the investigation of acts committed against women, application of the Convention of Belém do Pará depends on the absolute certainty about whether or not the act to be investigated constitutes violence against women in the terms of that Convention. In this regard, it should be stressed that it is by compliance with the duty to investigate established in Article 7 of the Convention of Belém do Pará that, in different cases, certainty can be reached on whether or not the act investigated constituted violence against the woman. Consequently, compliance with the obligation cannot be made dependent on this certainty. Consequently, it is sufficient that the act in question has material characteristics that, reasonably considered, indicate the possibility that it was an act of violence against a woman in order to give rise to the obligation to investigate in the terms of the Convention of Belém do Pará, 255 256 Cf. Case of Velásquez Rodríguez. Merits, supra, paras. 127, 128 and 129, and Case of J., supra, para. 305. Cf. International Responsibility for the Promulgation and Enforcement of Laws in Violation of the Convention (Arts. 1 and 2 American Convention on Human Rights). Advisory Opinion OC-14/94 of December 9, 1994. Series A No. 14, para. 35, and Case of J., supra, para. 349.