Rights (IACtHR) in 2010, as well as APT submissions to the Mexican Supreme Court in 2014 and the Costa Rica Constitutional Court in 2017. While each of the above mentioned submissions holds its own value, the APT amicus curiae brief presented in the IACtHR case of Teodoro Cabrera García and Rodolfo Montiel Flores against the United Mexican States 1 perhaps constitutes one of the most significant examples of how CSOs third-party interventions may effectively contribute to elucidating international standards on the exclusionary rule, and accordingly promote its effective implementation at the national level. The APT amicus curiae brief provided analysis and comparative law jurisprudence on the duty of States to prevent torture and to ensure that evidence is not obtained through this practice. The document focused on different aspects of the principle of non-admissibility of evidence obtained by torture, including its absolute and non-derogable nature; its purpose and relationship with fair trial rights; as well the burden of proof. Finally, the piece tackled the evidentiary value of confessions, with a particular reference to the principle of procedural immediacy in Mexico. In its judgement, the IACtHR considered several arguments enclosed in the APT amicus curiae brief. Most importantly, it concluded that Mexico breached Article 8.3 of the American Convention on Human Rights, by not excluding evidence obtained by torture in judicial proceedings (Judgement of 26 November 2010, para. 177). Further, in line with APT’s arguments, the Court stated, “statements obtained under duress are seldom truthful, because the person tries to say whatever is necessary to make the cruel treatment or torture stop”. Consequently, “accepting or granting evidentiary value to statements or confessions obtained by coercion, which affect the person or a third party, constitutes, in turn, an infringement of a fair trial.” Additionally, the Court noted that “the absolute nature of the exclusionary rule is reflected in the prohibition on granting probative value not only to evidence obtained directly through coercion, but also to evidence derived from such action" (Judgement of 26 November 2010, para. 167). II. CSO-led initiatives that support the effective implementation of the exclusionary rule in practice: a new opportunity for CSO engagement CSOs can also play a critical role on a broader level, particularly by addressing institutional incentives and other systemic factors that prevent the effective implementation of the exclusionary rule in practice. As recent research shows, the effective implementation of the exclusionary rule is often tied to how the criminal justice system operates. For instance, criminal justice systems that rely mostly on confessions as the main evidence on which convictions are founded, will most likely face challenges in ensuring effective application of the exclusionary rule in practice. Conversely, criminal justice systems that exclude confession based evidence are likely to be more effective in the implementation of the exclusionary rule. In this context, the new Principles on Effective Interviewing for Investigations and Information Gathering, also known as the Méndez Principles, are a concrete example of a CSO-led initiative that offers solution-oriented guidance for the effective implementation of the exclusionary rule in domestic law and practice, while addressing existing incentives and other systemic factors that impede the correct functioning of criminal justice systems in line with international standards on torture. The Principles are the culmination of a four year consultation process led by the APT together with the Anti-Torture Initiative (ATI) and the Norwegian Center for Human Rights (NCHR). The process involved police investigators, academics, human rights lawyers and CSO representatives from all over the world, and the Principles were drafted by a multidisciplinary, gender balanced, and geographically representative group of international experts. 32