153. Similarly, due diligence in a forensic investigation into a death requires maintaining the chain of custody of all the evidence. 251 The Court has indicated that this consists in keeping a precise written record supplemented, as appropriate, by photographs and other graphic elements, to document the history of the evidence as it passes through the hands of the different investigators in charge of the case. The chain of custody may continue beyond the trial and the conviction of the perpetrator, because old evidence, preserved appropriately, could be used to absolve a person who has been convicted erroneously. The exception to this are the remains of victims who have been positively identified and that can be returned to their family for burial, with the reservation that they cannot be cremated and could be exhumed for further autopsies.252 154. Regarding autopsies, as the Court has indicated, their purpose is to collect, at a minimum, information to identify the deceased, and the time, date, cause and manner of death, They must respect certain basic formalities, such as recording the date, starting and finishing times and place of the autopsy, as well as the name of the official performing it. In addition, it is necessary, inter alia, to photograph the corpse adequately; radiograph the body before it is removed from its pouch or wrappings and before and after undressing the body, documenting any evidence of injury. Any teeth that are absent, loose or damaged should be recorded, as well as all dental work, and the genitalia and surrounding areas examined carefully for sign of sexual abuse. In addition, the United Nations Manual indicates that the autopsy should record the body position and condition, including body warmth or coolness, lividity and rigidity; the deceased’s hands should be protected; the ambient temperature noted, and any insects collected.253 155. The Court recalls that it is uncontested that, at approximately 8.30 a.m. on August 12, 2005, Claudina Velásquez left her home, accompanied by her brother, to go to the university. According to the members of her family, after Claudina advised them that she was at a party and they had a last telephone call with her around 11.45 p.m., they lost contact with her. Her parents began to look for her when they were advised at around 2 a.m. on August 13, 2005, that she could be in danger by someone who said that she had spoken to her by telephone, and who went directly to the family home to alert them to this situation. At 2.12 a.m. the PNC received a report of a possible sexual assault in Colonia Roosevelt on the 110 number. At around 2.50 or 2.55 a.m., Claudina Velásquez’s parents called the PNC. In response, a patrol car came to the main guardhouse of Colonia Panorama at approximately 3 a.m. The parents following the police patrol car looking for their daughter from the main entrance of Colonia Panorama to the entrance of Colonia Pinares, where the police agents told them that they had to “wait at least 24 hours” to be able to report that Claudina Velásquez was missing. From 3 a.m. to 5 a.m., Claudina Velásquez’s parents continued to search for her with the help of family members and friends. At around 5 a.m., Claudina’s parents went to the police station to report that she was missing. There, they were again told that they should wait 24 hours. At approximately the same time, the Guatemalan Voluntary Fire Service received an anonymous call concerning the discovery of a corpse in Colonia Roosevelt and proceeded to the site. Also, two PNC agents went there at around 5.30 a.m. Around 6.30 a.m., personnel of the Public Prosecution Service also arrived there (supra paras. 52 to 55). Cf. Case of González et al. (“Cotton Field”) v. Mexico, supra, para. 301, and Case of the Human Rights Defender et al. v. Guatemala, supra, para. 207, citing the United Nations Manual on the Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions (Minnesota Protocol), supra. 252 Cf. Case of González et al. (“Cotton Field”) v. Mexico, supra, para. 305, and Case of the Human Rights Defender et al. v. Guatemala, supra, para. 207. 253 Cf. Case of González et al. (“Cotton Field”), supra, para. 310, and Case of Veliz Franco et al. v. Guatemala, supra, para. 194, citing the United Nations Manual on the Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions (Minnesota Protocol), supra. 251 56