158. The IACHR observes, first, that it is evident that the witness testimony was neither obtained nor preserved with due diligence, because of the lack of adequate protection for witnesses in light of the threats they received to discourage them from cooperating in the search for the truth, and given the reported breach of confidentiality in the investigation. The Commission also observes that the State showed no evidence of having made efforts to conduct disciplinary investigations into this type of negligence in the procedural advancement of the investigations. 159. Additionally, from the information submitted, the IACHR notes that the authorities in charge of the investigation in this case failed to follow procedures that were in keeping with international standards when they inspected the body and the crime scene. In the corpse inspection certificate there is no indication that the scene of the crime was examined to collect evidence of criminal interest. For example, there are no comments about the articles found on Nelson Carvajal and their position in relation to the corpse, and there is no indication that they examined the site to collect and preserve all of the blood, hair, fiber and thread, or fingerprint samples. Nor is there any indication that a detailed crime scene sketch drawn to scale was made to record the location of the corpse, the vehicles, surrounding buildings, and items found at the scene. Corpse inspection certificate No. 042 contains no record of the vehicles located in the area, or if the area was protected for this purpose. 160. The Commission also notes that from the crime scene the authorities collected “1 bullet nose and 6 shell casings around the body” of Nelson Carvajal Carvajal. This material was not submitted for ballistic testing, according to the report drafted in February 2000 by the TIU, which states that “no type of shell casings were received for ballistic analysis.” There is no indication in the file as to whether these casings were lost or where the evidence was taken. 161. The abovementioned defects and omissions demonstrate a lack of due diligence on the part of the State in the recovery and preservation of evidence. The IACHR finds that this could have contributed to the difficulty in determining the truth of the events and identifying and, if appropriate, punishing the perpetrators. c. Lines of investigation and the identification of the perpetrators 162. In complying with their duty to investigate and prosecute all perpetrators of violence against journalists, States must act with due diligence and exhaust the lines of inquiry related to the victim’s practice of journalism. In this respect, the Inter-American Court has underscored that the due diligence requirement means that the criminal investigations must exhaust all logical lines of investigation. In particular, “due diligence” demands that the investigations conducted by the State take account of “the complexity of the facts, the context in which they occurred, and the systematic patterns that explain why the events occurred,” ensuring that there are no “omissions in gathering evidence or in the development of logical lines of investigation.”153 163. Indeed, the obligation to conduct the investigation with due diligence and exhaust all logical lines of investigation is particularly relevant in cases involving violence against journalists, given that an investigation that fails to consider the context, including the professional activity of the journalist, will be less likely to obtain results and will probably raise doubts about the authorities’ willingness to solve the crime.154 In this regard, the Inter-American Court has stressed the importance of exhausting the logical lines of investigation relating to the professional practice of journalists who have been the victims of violence.155 153 I/A Court H.R., Case of the Rochela Massacre v. Colombia. Merits, Reparations and Costs. Judgment of May 11, 2007. Series C No. 163. Para. 158; I/A Court H.R., Case of Manuel Cepeda Vargas v. Colombia. Preliminary Objections, Merits, Reparations and Costs. Judgment of May 26, 2010. Series C No. 213. Para. 106-110 & 167. 154 IACHR. 2013 Annual Report. Report of the Office of the Special Rapporteur for Freedom of Expression. Chapter III (Violence against Journalists and Media Workers: Inter-American Standards and National Practices on Prevention, Protection and Prosecution of Perpetrators). OEA/Ser.L/V/II.149. Doc. 50. December 31, 2013. Para. 203. 155 I/A Court H.R., Case of Vélez Restrepo and Family v. Colombia. Preliminary Objection, Merits, Reparations, and Costs. Judgment of September 3, 2012. Series C No. 248. Para. 211.