clear breach of the duty to investigate with due diligence, there could be deliberate abetment (encubrimiento) in this case. 93. Added to this evidence of abetment is the fact that Mrs. Acosta, as an accused person, encountered difficulties both in giving her statement in the preliminary investigation at the location to which she fled for safety reasons, and in presenting evidence during the preliminary proceeding in the case because she had not been legally recognized as a party in time. Those difficulties amounted to an obstruction by the authorities, preventing her from presenting information to show the possible part played by Messrs. Tsokos and Martínez in Mr. García Valle's murder. The foregoing is significant bearing in mind that Mrs. Acosta named Messrs. Tsokos and Martínez in her initial statement as alleged instigators. The Commission also notes as further evidence of abetment that Mrs. Acosta's counsel was only formally granted the right to participate in the proceeding on May 13, 2002, the very day on which the dismissal was issued, by which time he could no longer present evidence. 94. The Commission finds that even after the acquittal the domestic authorities continued deliberately to omit to carry out an investigation to identify the instigators of Mr. García Valle's murder, even though it was imperative to do so based on the information that continued to emerge. 95. Thus, the Commission notes that following the acquittal, the National Police presented to the judge presiding over the case a certificate of employment which showed that Iván Argüello—the perpetrator—worked as a security guard for Peter Tsokos, together with the ballistics report that showed that Peter Tsokos was the owner of the firearm used to take Mr. García Valle's life. In addition, the record shows that both the Office of the Prosecutor and Mrs. Acosta's legal counsel requested the relevant authorities to take both exhibits into consideration. Indeed, the IACHR finds that one of the arguments used by the Assistant Prosecutor in Managua to request the Supreme Court of Justice to annul the definitive dismissal of May 13, 2002, was the failure to give consideration to the aforesaid exhibits194. 96. In spite of the fact that the new evidence highlighted the need to explore and exhaust an investigation into the identity of the instigators and the motive for the murder even more clearly, the domestic authorities, without offering an explanation, refused to reopen the investigations into Messrs. Tsokos and Martínez. To the contrary, when the second perpetrator—Wilberth Ochoa—was named as a suspect in the proceeding, he was not questioned about the possible reasons for Mr. García Valle's murder or the possible relationship between himself or Iván Argüello— as perpetrators—and the alleged instigators. Particularly serious is the fact that, although Iván Argüello told the press that Peter Tsokos had sent him to murder Mr. García Valle, there is nothing in the record to show that the authorities attempted to follow up on that statement or make inquiries in that regard. 1.2. The lack of investigation of the third perpetrator 97. As this report has already noted, the obligation effectively to investigate acts that violate human rights entails making every effort to identify and punish all those responsible for such acts.195 In that regard, the IACHR notes that according to the United Nations Manual on the Effective Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions, one of the focuses of investigations of crimes of this type must be to identify everyone who was involved in the homicide196. 98. In this case, in addition to the deliberate omission to investigate the identities of the instigators of Mr. García Valle's murder, the IACHR finds that various irregularities occurred in the course of the investigation that obstructed the identification of the third perpetrator, including: (a) failure to question 194 Appendix 134. Response of the Office of the Assistant Prosecutor of Managua regarding the mistreatment of the appellant filing the annulment appeal. File No. 2019-2004 of the appeal for annulment to the Supreme Court, folios 80-86. Appendix to the petitioners’ communication of July 13, 2007. 195 I/A Court H.R., Case of Myrna Mack Chang v. Guatemala. Merits, Reparations and Costs. Judgment of November 25, 2003. Series C No. 101, par. 275. 196 See U.N. Doc E/ST/CSDHA/.12 (1991).