Draft:Principles on Effective Interviewing for Investigations and Information Gathering (Mendez Principles)

The Principles on Effective Interviewing for Investigations and Information Gathering, also known as the Mendez Principles, is a document drafted by international experts providing a concrete alternative to interrogation methods that rely on coercion (currently available in 11 languages). A global Steering Committee of 15 members guided the process, consulting an Advisory Council comprising more than 80 experts from over 40 countries. The process was coordinated by the Association for the Prevention of Torture, the Anti-Torture Initiative and the Norwegian Centre for Human Rights. The final text represents four years of work and analysis grounded in a scientific research base, documented good practices, established international law and professional ethics.

The document is built on six principles. These are:
 * Effective interviewing is instructed by science, law and ethics.
 * Effective interviewing is a comprehensive process for gathering accurate and reliable information while implementing associated legal safeguards.
 * Effective interviewing requires identifying and addressing the needs of interviewees in situations of vulnerability.
 * Effective interviewing is a professional undertaking that requires specific training.
 * Effective interviewing requires transparent and accountable institutions.
 * The implementation of effective interviewing requires robust national measures.

These principles are also called the Mendez Principles to honor the former UN Special Rapporteur on Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, Juan E. Méndez. The document grew from a thematic report submitted by Prof. Méndez to the United Nations (UN) General Assembly in 2016 calling for the development of international standards for interviews based on scientific research, legal safeguards and ethical principles. The Mendez Principles represent the realization of that call.

Michelle Bachelet, then UN High Commissioner of Human Rights, opened the launch event for the document on June 9, 2021. Since that date, more than 50 countries from all regions have supported them, and a growing body of UN, regional and national documents/jurisprudence reference the document. Moreover, international projects have been launched to implement the principles to expand the global trend toward non-coercive interviewing, while a closely related joint UN manual for criminal investigations was validated in November 2024 to continue the shift away from confession-driven methods (see below).

Background and Purpose
International law universally condemns torture and ill-treatment as an absolute prohibition. The Mendez Principles offer tools by which to realize this goal in the context of gathering information from an individual. While they have not been officially endorsed by a UN body, they are similar to other protocols, such as the Mandela Rules, Istanbul Protocol and Minnesota Protocol, in that this document is an authoritative resource on law and practice which is not legally binding. They are rooted in practical scientific research on how best to gather factual information, combining legal norms with a comprehensive guide for conducting interviews that uphold accuracy and professionalism. And they draw attention to effective, legal and ethical methods that law enforcement and security personnel use across a variety of countries. Notably, while its lineage can be traced globally, the analogous method of investigative interviewing has been developing across Europe and beyond for decades and valuable scientific research on this matter has been pursued by the High-Value Detainee Interrogation Group in the United States.

The Principles respond to the persistent challenge of torture and ill-treatment during investigations and intelligence gathering, including in situations of armed conflict or public emergency, despite an extensive international legal framework prohibiting such practices. They build on a vast scientific literature that establishes rapport-based, non-coercive interviewing techniques as the most effective means of gathering accurate and reliable information. They also draw on extensive literature underscoring the ineffectiveness and counter-productive property of torture and abuse.

The Mendez Principles seek to transform how authorities question detainees and conduct interviews across a range of straightforward and complex scenarios. They are applicable to all interviews conducted by authorities, including police, intelligence, military, immigration and customs officers, and related administrative bodies. They cover interviews with suspects, witnesses, victims, and other persons of interest.

The global consortium of experts who crafted the text came from various fields, including law enforcement, psychology, national security, military, intelligence gathering, human rights, and criminology. By operationalizing the presumption of innocence, the Principles contribute to more just, safe, and inclusive societies, aligning with the UN Sustainable Development Goals.

Analytical Structure
Analytically, the Mendez Principles hold that security investigation and interviewing can be lawful and practical. Lawful behavior generates effective interviewing. Effective interviewing stems from adherence to the law. In this respect, the Mendez Principles do not simply maintain that interviewers must comply with the law or that their responsibilities are compatible with legal norms as others have argued. They hold that the motivations to be lawful and practical are interdependent.

This represents a practical and theoretical advancement. The practical advancement is to offer a method that can be implemented anywhere. The more lawful the behavior, the more effective the outcomes. On the other hand, learning to interview effectively professionalizes and reinforces lawful behavior. Unlawful behavior generates poor conditions for acquiring actionable information. And the more dependent investigators become on coercive investigation, the more deprofessionalized and lawless they become.

The safeguards law enforcement must guarantee in the course of an interview coincide with a successful interview in the following manner. Effective interviewing respects rights pertaining to the flow of information (information about rights, information about the reasons for arrest and charges, right to remain silent); rights pertaining to access (to interpretation, to notify a third party, access to a lawyer; access to a doctor and an independent medical examination, to contact the outside world); and the right to documentation and accountability (registration of persons held in detention, full recording of the interview, to review and sign the interview record, habeas corpus, and the existence of effective and independent complaints mechanisms).

The theoretical advancement is to put into question the arguments in favor of coercive interrogation. These arguments hold that practical interrogation and lawful compliance are at odds, if not in principle, in many situations that matter to law enforcement. Examples like the ticking bomb scenario take this assumption for granted. The Mendez Principles offer an alternative: empirically grounded practices applicable to all situations even when time is short, and a bomb is ticking.

The argument is a species of "ought implies can." A car is not faster than a bicycle if it has no gas. Unlawful interrogation is not faster than legal action if it yields poorer actionable results. Sometimes officers pursue coercive interrogation and torture even when they know they cannot achieve positive outcomes. They may pursue harsh methods to generate a false confession, blackmail individuals, please superiors, achieve promotions, and mislead the public. More generally, they may engage in cruel techniques as part of a broader schema, including terror and retribution. However, none of these goals pertain to the pursuit of accurate and reliable information – the aim of effective interviewing as it is defined in this document.

Formal Structure
Formally, the document has six sections, each addressing one of the six principles for effective interviewing. Each section consists of advice, counsel, and practical steps to be taken.

Principle 1 – On Foundations

This initial Principle establishes the groundwork for effective interviewing practices with three critical pillars: scientific foundations, legal grounds, and widely accepted professional ethics. Together, these components provide the basis for ensuring that interviews are conducted in a manner that upholds all the central elements at stake.

Principle 2 – On Practice

The second Principle outlines a process for conducting interviews, prioritizing the collection of accurate and reliable information. It underscores the importance of legal safeguards, ensuring a non-coercive environment before the interview, establishing and maintaining rapport during the interview, and conducting assessment and analysis at the interview's conclusion.

Principle 3 – On Vulnerabilities

Recognizing the inherent power imbalance that all interviewees face, this Principle highlights the interview as a situation of vulnerability. It also provides guidance on addressing situations of heightened vulnerability and offers a framework for assessing and mitigating potential risks during interviews.

Principle 4 – On Training

Effective interviewing relies on well-trained professionals. It emphasizes the need to train interviewers and promote continuous professional development to ensure that interviewers are able conduct effective interviews.

Principle 5 – On Accountability

Accountability is a cornerstone of effective interviewing practice. This Principle outlines institutional procedures and review mechanisms, effective record-keeping, prevention and reporting of misconduct, external oversight and independent monitoring, as well as processes for handling complaints, conducting investigations, and providing redress and reparations when necessary.

Principle 6 – On Implementation

The final Principle focuses on application within domestic legal frameworks. It addresses institutional culture and capacity, the role of judicial authorities, and the dissemination of these Principles to ensure their widespread adoption and consistent application.

Empirical Grounding
The Méndez Principles derive their foundation from the intersections of science, law, and ethics, with the underlying sources of the document harmonizing these essential pillars.

Effective Practice
The Mendez Principles build on research from various disciplines, including psychology, criminology, sociology, neuroscience, and medicine. In particular, "Principle 2, On Practice" is built on well-established evidence-based inquiry into non-coercive interviewing techniques.

Extensive research confirms the effectiveness of an information-gathering approach to interviewing. Rapport-based, non-coercive methods offer a suite of techniques that trained professionals can apply successfully across various scenarios, including interviews with criminal suspects, victims, witnesses, and intelligence sources.

Establishing and maintaining rapport is the core of these practices. Interviewers achieve this by establishing common ground, identifying shared interests, identities, or attitudes, and by employing active listening skills. Mastering these skills fosters a collaborative relationship between interviewer and interviewee, enabling more effective communication. Building rapport is firmly influenced by the interviewer's ability to cultivate trust and convey respect for human dignity, while demonstrating genuine empathy and a commitment to fair treatment. Such trust includes granting interviewees autonomy over what they choose to disclose. All these processes make it more likely interviewers will collect accurate and reliable information.

Significantly, the Mendez Principles incorporate the latest insights from research on human memory. This work identifies factors that enhance or degrade memory retrieval. Effective Interviewing methods prioritize detailed and accurate reporting by interviewees while mitigating factors that could influence their accounts. Researchers identify several methods including employing open-ended, non-suggestive questioning and affording individuals the opportunity to freely recall information from their memory without interruption. Moreover, strategically planned questioning can direct interviews toward essential matters and enable interviewers to assess whether information provided agrees with that which has been previously collected.

Fundamentally, extensive research underscores the multifaceted benefits of rapport-based, non-coercive interviewing. These practices stimulate open communication, facilitate memory retrieval, enhance the accuracy and reliability of information, enable the exploration of information veracity, increase the likelihood of obtaining rich and genuine admissions, and crucially, reduce the risk of eliciting false information or false confessions.

Ineffective Practice
Recent research also underscores the dangers of coercive practices during interviews. Coercion reduces cooperation and increase resistance, as well as backfires by hindering the collection of factual information. Neuroscience studies reveal that mental and physical coercion can interfere with and potentially damage the memory-retrieval capacity of the brain.

Wide scientific evidence highlights the detrimental impact of coercive interviewing methods on generating reliable information and point to an increasing likelihood of obtaining false confessions. The consequences have far-reaching implications, including wrongful convictions, compromised intelligence gathering and impunity for the truly guilty.

Psychologically coercive questioning methods are similarly compromised. Manipulating perceptions of culpability or consequences elicit incorrect information and increase rates of false confessions. Threats or enactments of physical harm during interviews induce heightened stress levels, impairing memory retrieval and diminishing the recall of accurate or reliable information.

Additionally, research underscores how leading or suggestive questions compromise an interviewee's memory and the information they provide. These tactics are particularly concerning when applied to interviewees who have a heightened vulnerability due to characteristics such as age, intellectual or psychosocial disabilities.

Furthermore, a common misconception prevails that accurate lie detection can be based on nonverbal cues, such as emotional responses, body language, or physiological signals. However, scientific research consistently debunks these assumptions, highlighting how unreliable such methods are for detecting deception.

While coercion is shown to be less effective and counterproductive through research, the scientific foundations supporting effective interviewing methods illuminate a path towards obtaining truthful information. By adhering to evidence-based approaches rooted in psychology, neuroscience, and other relevant fields, interviewers can cultivate trust, encourage cooperation, and ensure the integrity of the information, as well as the process.

Legal Sources
The framework for the Mendez Principles comes from treaty obligations, customary international law, non-derogable peremptory (jus cogens) norms, and international, regional, and national jurisprudence. This legal foundation ensures the applicability and adaptability of the framework across diverse legal systems.

Central to these legal underpinnings are international human rights norms and standards that are key for the practical implementation of the interview framework. These include the prohibition of torture and other ill-treatment, the right to liberty and security, the presumption of innocence, the right to remain silent, the right to a fair trial, and the right to be free from discrimination. Notably, the absolute prohibition of torture, binding on all States and applicable in all circumstances, underscores the imperative to avoid coercion that can amount to ill-treatment in interviewing methods and practices.

The presumption of innocence stands as a cornerstone of justice, signifying that individuals are treated as innocent unless or until they are proven otherwise through a fair and impartial legal process. It dictates that the burden of proving guilt rests on prosecutorial authorities, supported by affirmative evidence presented in a court of law. Adhering to the legal principle in this context means collecting accurate and reliable information that can constitute lawful and actionable evidence in legal proceedings. This principle also encompasses the right to remain silent and safeguards against compelled self-incrimination. Additionally, it obligates authorities to ensure that all interviewees experience their human rights without any form of discrimination and are treated equitably under the law.

The exclusionary rule, a fundamental component of international legal standards, is intrinsically linked to the prohibition of torture and other forms of ill-treatment. This rule declares that any information or statements obtained through torture or ill-treatment are illegal and inadmissible in any legal proceedings, except when such evidence is used against those accused of mistreatment. By upholding this rule, the international legal framework condemns and prevents the use of coerced confessions or statements, thereby safeguarding the integrity and fairness of legal proceedings and protecting individuals.

Moreover, the legal foundation incorporates essential principles related to the use of force,  non-lethal weapons,  corporal punishment, and instruments of restraint. It emphasizes the importance of maintaining up-to-date official records of individuals deprived of liberty, strictly regulating the use of solitary confinement,    and closely managing disciplinary sanctions. The legal norms seek to safeguard the personal liberty and security of all individuals and prohibit practices such as enforced disappearance, secret detention, and prolonged incommunicado detention.

Furthermore, the legal framework underscores the necessity of lawful arrest and detention procedures, firmly set out in legislation and consistent with international law. It emphasizes that deprivation of liberty must be based on justifiable and substantiated reasons and considers non-custodial alternatives where appropriate. Authorities should only apprehend and detain individuals after thoroughly evaluating their specific circumstances and when there are valid and well-founded concerns that the person may pose risks such as fleeing, tampering with evidence, exerting influence over witnesses, or engaging in further criminal activities.

These legal and procedural safeguards are not simply an addition to effective interrogation methods. On the contrary, they are integral to the comprehensive interview process. The Mendez Principles show on the basis of the best scientific evidence that legal and investigative work go hand in hand, protecting interviewees' human rights while upholding the integrity of the information obtained during interviews. They protect both the individual and society itself, ensuring the legitimacy of the entire investigative and legal process.

Professional Ethics Sources
Effective interviewers adhere to the highest ethical standards, guided by professional regulations and codes of ethics that outline the purpose, values, and expected conduct. These ethical principles govern all aspects of an official's duties, including interviews, in accordance with international legal obligations. Commitment to ethical interviewing prevails even in situations of intense pressure, such as limited time or demands for immediate results. Interviewers, exercising their authority while upholding the law, strive to achieve ethical outcomes that can withstand ethical, judicial, and public scrutiny.

Professional codes of ethics for law enforcement officials underscore the significance of respect, fairness, and honesty as the fundamental pillars of all interviews. Officials are also required to wield state authority in a lawful, fair, and responsible manner at all times. Any illicit action performed in an official capacity constitutes an abuse of power.

Interviewers bear an ethical duty to employ the most effective methods available that safeguard the rights and dignity of interviewees while preserving the integrity of the process. Likewise, they have an obligation to abstain from coercive tactics, as these methods not only inflict harm on interviewees but also compromise the goal of acquiring accurate information.

Global Recognition, Citation and Implementation
1. Reference to the document has been made by United Nations bodies, regional and national documents/jurisprudence beginning in 2021. This recognition is an acknowledgment of the document's persuasive authority, validity, and quality. It indicates that these organizations or bodies have officially recognized the document as a reputable source of information or guidance within their respective spheres of influence. Reference to the document has been made by the following bodies thus far:


 * UN Resolutions and Declarations
 * UN General Assembly
 * UN Office on Drugs and Crime
 * UN Human Rights Council
 * UN Human Rights Bodies, UN Treaty Bodies and Special Procedures
 * UN High Commissioner for Human Rights
 * UN Human Rights Committee
 * UN Committee Against Torture
 * UN Subcommittee on Prevention of Torture
 * UN Working Group on Arbitrary Detention
 * UN Special Rapporteur on Torture
 * Resolutions and references by Regional Organisations and Human Rights Bodies
 * African Union
 * Council of Europe
 * European Union
 * Organization of American States
 * OSCE Office for Democratic Institutions and Human Rights
 * Within National Jurisprudence
 * Colombia

2. In 2023, the European Cooperation in Science and Technology (COST) funded a project to establish networks to implement the Mendez Principles. This COST Action (ImpleMéndez) involves a strategy of convening regional and in-country networks of researchers, practitioners and policy makers working with each other and with the Action Team to enable wider implementation of the principles.

3. Another document of a similar nature was released in February 2024 which outlines the practical steps to implement the Mendez Principles in a policing context: The Manual on Investigative Interviewing for Criminal Investigation. It was approved by more than 30 UN experts and state representatives and is the product of a collaborative effort between the UN Department of Peace Operations, the Office of the High Commissioner for Human Rights, and the UN Office on Drugs and Crime. The manual serves as a guiding document for the United Nations Police officers in their mandated roles, and establishes a resource for police development and capacity-building across the UN system.