A/HRC/36/50/Add.1 measures, including prosecutions, truth commissions and historical and cultural works. One example of this advance concerns the strengthening of professional competence in forensics since the early 1980s, when the Abuelas de la Plaza de Mayo first engaged United Statesbased scientists to help them trace their missing children and grandchildren. 23 Emerging out of the Argentine experience, a small but dedicated group of scientists pioneered new methods of DNA testing, which was put into practice also in Chile, Guatemala and Peru. These groups were again called on for their expertise by the International Tribunal for the Former Yugoslavia and the International Tribunal for Rwanda. In 1996, the International Commission on Missing Persons was created to investigate the roughly 40,000 people missing as a result of the conflict in the former Yugoslavia. The field of forensic investigation of human rights crimes has proliferated, with centres of expertise now set up in many countries. 36. Documentation has also improved, aided by technological advances and international cooperation. Professional standards and methodologies for taking witness testimony and collecting official and unofficial documents have been strengthened, and are all critical to ongoing or later transitional justice efforts. Technological innovations have helped create tools for the documentation and analysis of large sets of data. Archiving, including preservation but also classification and access, has benefited immensely from new technologies.24 B. Advances in prosecutions 37. Prosecutions provide recognition to victims as rights holders; they provide an opportunity for the legal system to establish its trustworthiness; they strengthen the rule of law; and finally, in doing all of the above, they can contribute to social reconciliation. The aftermath, however, of gross violations of human rights and serious violations of international humanitarian law pose particular challenges for prosecutions. Usually only a fraction of those who bear responsibility for violations are ever investigated, because of the high number of suspected perpetrators, the relative scarcity of financial and human resources, capacity and will, and the fact that in many transitions the predecessor regime or forces maintain a certain power. 1. Right to justice: coping with amnesties 38. Some courts have nullified amnesties outright, articulating the limits of legislative power to grant amnesties in two main ways. First on constitutional grounds, as the Peruvian Constitutional Tribunal did, by declaring two successive amnesty laws unconstitutional and arguing that they were part of a plan to guarantee impunity at odds with article 1 of the Peruvian Constitution which establishes that “the defense of the human person and respect for [his or her] dignity are the supreme purpose of society and the State”.25 39. Second, some courts have appealed to international law or jurisprudence to nullify amnesty laws. The Supreme Court of Argentina, for instance, in the Simón case, declared the Final Stop and Due Obedience Laws unconstitutional. The Supreme Court argued in that case that article 75 (22) of the Constitution, which establishes that “treaties and concordats have a higher hierarchy than laws”, makes various instruments, including the Universal Declaration of Human Rights, the International Covenant on Civil and Political Rights and the American Convention on Human Rights, constitutional, and that those instruments limit the power of the legislature to grant such amnesties. 26 40. Even countries that have not nullified amnesties have found ways of mitigating their worst consequences. One method has been to argue that the very concept of amnesty calls 23 24 25 26 Adam Rosenblatt, Digging for the Disappeared (Stanford University Press, 2015). A/HRC/30/42. Santiago Enrique Martín Rivas, Exp. No. 679-2005-PA/TC, 2 March 2007, Constitutional Tribunal of Peru, especially paras. 56 ff. Simón, Julio Héctor y otros s/ privación ilegítima de la libertad, etc., S.1767.XXXVIII, 14 June 2004, Supreme Court of Argentina, para. 16. 9