77 these items, where they were sent, or in what conditions they were conserved.318 Some of this evidence was not analyzed for more than six years. Indeed, on November 22, 2007, while organizing boxes of evidence relating to the cases processed in Ciudad Juárez, a box with samples of the hair and bones of the victims was located, with no indication whatsoever about why this evidence was found in that place, and without any indication of the procedures established to protect this evidence; in other words, without the required chain of custody.319 305. On this point, the United Nations Manual indicates that due diligence in the legal and medical investigation of a death requires maintaining the chain of custody of each item of forensic evidence.320 This consists in keeping a precise written record, complemented, as applicable, by photographs and other graphic elements, to document the history of the item of evidence as it passes through the hands of the different investigators responsible for the case. The chain of custody can extend beyond the trial, sentencing and conviction of the accused; given that old evidence, duly preserved, could help exonerate someone who has been convicted erroneously. The exception to the foregoing is the positively identified remains of victims, which can be returned to their families for burial, on condition that they cannot be cremated and may be exhumed for new autopsies.321 306. The Court concludes that, in this case, irregularities occurred as regards: (i) the failure to identify with precision the circumstances of the discovery of the bodies; (ii) the negligible rigor in the inspection and preservation of the crime scene by the authorities; (iii) the improper handling of some of the evidence collected, and (iv) the methods used were inadequate to preserve the chain of custody. 307. In addition, the Tribunal observes that, this case is not the only one in which negligence in the collection of evidence has been reported (supra para. 150). Indeed, the Office of the Special Prosecutor for the Investigation of the Murders of Women in Ciudad Juárez indicated that between 1993 and 2005, frequently “the content of the expert appraisals, basically those of on-site criminology, did not correspond to the affidavits drawn up at the site of the facts by the official of the respective Public Prosecutor’s Office.”322 Furthermore, there were numerous irregularities concerning 318 During these searches by the next of kin, they found the voter credentials and the employment credentials of Claudia Ivette of González (Cf. affidavit concerning the place and objects issued on February 24, 2002, by the official of the Public Prosecutor’s Office attached to the Office of the Special Prosecutor for the Investigation of the Murders of Women, case file of attachments to the application, volume IX, attachment 63, folios 2923 and 2924); preliminary affidavit concerning the place and objects issued on February 25, 2002, by the official of the Public Prosecutor’s Office attached to the Office of the Special Prosecutor for the Investigation of the Murders of Women, case file of attachments to the application, volume IX, attachment 64, folios 2927 and 2928), and testimony given by Mrs. Monárrez Salgado before the official of the Public Prosecutor’s Office attached to the Office of the Internal Affairs Controller for the Northern Zone on July 23, 2006 (case file of attachments to the application volume IX, attachment 84, folios 3504 to 3507). 319 Cf. testimony given by an expert witness in chemistry attached to the Technical Office of Expert Services and Forensic Medicine of Ciudad Juárez before the official of the Public Prosecutor’s Office attached to the Joint Agency to Investigate the Murder of Women in Ciudad Juárez on March 15, 2008 (case file of attachments to the answer to the application, volume XXXVIII, attachment 50, folios 14072 to 14074). 320 Cf. Manual on the Effective Prevention and Investigation of Extralegal Executions, supra note 310. 321 Cf. statement made before notary public by expert witness Snow on April 17, 2009 (merits case file, volume XIV, folio 4225). 322 Cf. Office of the Special Prosecutor for the Investigation of Crimes related to the Murders of Women in Ciudad Juárez, Informe Final, supra note 87, folio 14580, and testimony of witness Doretti, supra note 141, folio 2326.