The Méndez Principles: A Focus on the Exclusionary Rule

CERL is pleased to present this article (and the entire Just Security series) based on the newly-released Principles on Effective Interviewing for Investigations and Information Gathering, also known as The Méndez Principles. Named for Juan Méndez, the former UN Special Rapporteur on Torture who in 2016 called for the creation of a universal protocol for lawful and humane interviewing standards, the principles provide guidance on conducting non-coercive and rapport-based interviews with legal and procedural safeguards. CERL has been an advocate of Mr. Méndez’s call for the protocol and welcomed him as the keynote speaker at CERL’s 2018 conference on interrogation and torture.–Claire O. Finkelstein, CERL Academic Director


The Méndez Principles: A Focus on the Exclusionary Rule, by Pavle Kilibarda and Gloria Gaggioli, was originally published in Just Security.


(Editor’s note: This article is part of a Just Security series on the newly released “Principles on Effective Interviewing for Investigations and Information Gathering,” an expert-led initiative responding to a 2016 appeal to the U.N. General Assembly by then-U.N. Special Rapporteur Juan E. Méndez to develop such standards. The series outlines the origins and the scientific, legal, and ethical underpinnings of the guidelines, also known as the “Méndez Principles” in honor of its co-chair.)

Among the main reasons ill-treatment persists in interrogations are inadequate interviewing techniques and the persistent myth that torture works and can produce useful results. International human rights bodies regularly deal with ill-treatment perpetrated in relation to interrogation. This was demonstrated again recently by the European Court of Human Rights in its judgment in Ćwik v. Poland on the application of the exclusionary rule to a statement extracted through torture by a criminal gang: the decision is remarkable as the Court expanded the rule to cover information gathered by a non-state actor. The judgment also coincides with growing awareness that interrogation standards are subpar and ineffective in many parts of the world. Setting clear-cut standards backed by empirical evidence is probably the best way of eradicating coercive interrogation in many situations.

Although many problems today stem from poor implementation and a lack of standards, challenges arise in relation to the law itself – Ćwik v. Poland demonstrates, for example, States’ reticence to treat abuse perpetrated by non-State actors as a human rights violation. This highlights legal issues that continue to appear in relation to the prohibition of torture worldwide – both in times of armed conflict and in peacetime, and in countries otherwise perceived as having a good human rights record. Torture and other forms of ill-treatment are, and will remain, an ethical low point in our collective experience as a species. And unless we exercise constant vigilance, especially in times of great strife, such abuses also become the point of no return in losing the struggle of several centuries to establish human beings and their individual rights and welfare as the raison d’être of modern States and the international community itself.

The prohibition of torture and ill-treatment constitutes one of the few domains of international law where there exists nigh-universal consensus among States and lawyers about the sheer strength of the legal norms governing the field. Not only has the prohibition of torture been proclaimed an absolute right of individuals everywhere, the notion of instrumentalizing pain and suffering for any purported higher benefit of society draws uniform abhorrence in all expert circles; and yet, like a recurrent disease, torture continues to creep back into global politics. This is not only because of the fiction that torture works, but also because human rights treaties, while providing a comprehensive legal framework, nevertheless contain gaps to be filled by practice, which itself has not always been consistent. The situation has led to legal uncertainty that some States have used to engage in practices that are not consistent with the object and purpose of human rights treaties.

One particular legal issue illustrates the point: the (perceived) imperfect character of the exclusionary rule.

Debating the Products of Torture

The age-old debate on the utility of the products of torture – statements, confessions, all types of information and material evidence, as well as the aptly-named “fruits of the poisonous tree” (i.e. derivative information/evidence) – is as lively today as it was in the immediate aftermath of the 9/11 attacks. The months and years following very nearly caused a full-scale paradigm shift in several established democracies from a rights-oriented approach to countering terrorism to utilitarianism instead.

The arguments have, admittedly, become more refined since the apex of the George W. Bush-era interrogational torture. One of those refined arguments is to consider that all products of torture are inadmissible regardless of their probative value; yet this is not necessarily the case for “lesser” forms of ill-treatment such as inhumane or degrading treatment or punishment. This observation was made by an influential human rights body, the European Court of Human Rights, in the controversial Gäfgen case in 2010. The Court found that, unlike the products of torture, real evidence produced by other forms of ill-treatment could in fact be admitted into criminal proceedings, provided it does not have a direct influence on the verdict and sentencing. Of course, that begs the question of why it is necessary to admit such evidence into proceedings in the first place. We call this lacuna the “Gäfgen gap.“

Although this case could be dismissed as an oddity of the European approach, other mechanisms have occasionally exhibited similar reservations when applying the exclusionary rule to products of cruel, inhuman, or degrading treatment (CIDT). For example, in spite of declaring Articles 3 to 15 of the United Nations Convention against Torture to be “obligatory as applied to both torture and ill-treatment” in its 2008 General Comment No. 2, the U.N. Committee against Torture nevertheless refused to apply Article 15 to CIDT in a 2014 case against Russia. Such inconsistencies are made possible because the application of Article 15 (the exclusionary rule) to CIDT is not explicit in the treaty. This is one of many reasons why the wording of the provision has been described as the weakest aspect of the document (see UN Doc. A/HRC/25/26, para. 17).

These problems arise when the fact that ill-treatment has taken place is not disputed; they grow exponentially when victims are required to prove that abuse has even happened. In the Mounir el-Motassadeq case, the German judiciary admitted into a terrorism trial information provided by the United States, for which there was a reasonable assumption that it had been obtained through torture, because the court had placed the onus on the accused to prove the unlawful origins of the evidence, along with an impossibly high standard of proof.

As highlighted by former U.N. Special Rapporteur on Torture Juan E. Méndez in 2014, “[i]t is (…) for the State to investigate with due diligence whether there is a real risk that a confession or other evidence was not obtained by lawful means, including torture or other ill-treatment” (UN Doc. A/HRC/25/60, para. 33). Applying criminal trial standards of proof with respect to the exclusionary rule is inherently flawed and threatens to undermine the rule’s very purpose, because determining whether a piece of evidence or information shall be admitted into proceedings is an entirely separate issue from proving that a torture suspect has, in fact, committed the crime.

Last but not least, there is a clear tendency among law enforcement agencies (i.e. police and security forces) to believe that their use of information tainted by torture is not prohibited by international law. For instance, Canada maintains a controversial ministerial direction that the authorities may rely on torture-extracted information coming from a foreign source in exceptional circumstances to decide to deprive someone else of their rights or freedoms if it is necessary to prevent loss of life or significant personal injury (although, presumably, it still cannot be used in “proceedings” as per Art. 15 of the U.N. Convention Against Torture).

We submit that even arresting or otherwise adopting administrative measures against a suspected terrorist to prevent acts of violence should be seen as a “proceeding” for the purpose of Article 15 of the UNCAT, regardless of whether the torture-tainted evidence is ever relied upon for an indictment or habeas corpus proceedings. This is crucial; otherwise, such practices legitimize ill-treatment by third parties, and run against the obligation to prevent torture and other CIDT. Although the human rights treaties do not deal with these issues explicitly, human rights bodies (See e.g. UN Doc. CAT/C/CAN/CO/6, para. 17) and U.N. experts have done a great deal to fill in the gap. For that reason, we may doubt that this substantial amount of jurisprudence and doctrine is disregarded in good faith.

Had there been universal awareness that the products of torture and CIDT are always unreliable and ethically unacceptable – another possible benefit of the Méndez Principles – the exclusionary rule would long since have been accepted as an indispensable element of the absolute prohibition of torture and CIDT. The rule would therefore similarly be regarded as containing no legal lacuna or gap.

As it is, human rights bodies and lawyers can still do much to improve the situation by achieving legal consistency in their own approach. Such consistency would allow a credible position to be maintained vis-à-vis those States that are not yet willing to a priori dispense with torture and CIDT and their products in all circumstances. An important method of eliminating ill-treatment is to disincentivize States from resorting to it by eliminating any possibility of achieving desired goals by resorting to such acts. Clearly, the exclusionary rule has a fundamental role to play in this regard, and only through its uncompromising application to all cases of ill-treatment can we ever hope to truly eradicate it.

(A launch event for the Méndez Principles took place on June 9th featuring speakers including U.N. High Commissioner for Human Rights Michelle Bachelet, Deputy Foreign Minister for Multilateral Affairs of Costa Rica Christian Guillermet Fernández, Ambassadors to the U.N. Mona Juul of Norway and Ramses Joseph Cleland of Ghana, U.N. Special Rapporteur on Torture Nils Melzer, and former U.N. Special Rapporteur on Torture Juan E. Méndez. A recording of the event is available here.)

About the Authors

Pavle Kilibarda

Pavle Kilibarda is a Teaching Assistant at the Geneva Academy and a PhD candidate at the Law Faculty, University of Geneva. His research focuses on general issues of public international law, particularly statehood recognition and the rights and obligations of states.

Gloria Gaggioli

Gloria Gaggioli (@GaggioliGloria) is the Director of the Geneva Academy since August 2020 and an Associate/ Swiss National Science Foundation (SNF) Professor at the Law Faculty of the University of Geneva. She is also member of the board of Geneva Call since August 2019.


CERL is grateful to Steven J. Barela, Senior Research Fellow at the University of Geneva in the Global Studies Institute, for his work in the publication of these articles on The Rule of Law Post. This work, which includes serving as Editor leading the Chairpersons’ Editorial Group of the Méndez Principles initiative, is supported by the Swiss National Science Foundation.

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