Lore Mergaerts, professor of criminological and legal psychology, KU Leuven (Belgium)
Roxanna Dehaghani, reader in law, Cardiff University (Wales)
This contribution is facilitated by and based upon work from COST Action CA22128 (ImpleMéndez), supported by European Cooperation in Science and Technology (COST).
Key messages
- Vulnerability is not a characteristic of a person alone. It emerges from the interaction between individual circumstances and situational dynamics.
- Principle 3 of the Méndez Principles offers an important and broad foundation for addressing vulnerability.
- Adequately addressing vulnerability requires hands-on guidance for practitioners on how to identify and respond to vulnerability in practice to uphold the dignity of the person and improve the quality of the information obtained.
Introduction
When discussing vulnerability in detention and effective interviewing, it is tempting to think immediately of specific groups of interviewees: children, persons with intellectual disabilities, people experiencing mental health conditions or non-native speakers. Yet, as will be discussed below, vulnerability is more complex than a list of categories.
A broad approach to vulnerability
The Méndez principles can be considered the ultimate result of a cooperation between academia and practice, integrating and operationalising the longstanding research and established insights from academic research into police questioning practices. The Méndez Principles consist of six principles, of which principle 3 specifically addresses the issue of vulnerability. In particular, it is stressed that effective interviewing requires that the needs of interviewees in situations of (heightened) vulnerability are identified and addressed (Méndez Principles, 2021). One of the strengths of Principle 3 is its broad and interdisciplinary understanding of vulnerability, including a variety of factors. Unlike traditional approaches that focus primarily on medical diagnoses or individual deficits, Principle 3 recognises that vulnerability can arise from both individual and situational factors. Foremost, Principle 3 acknowledges that in principle, as a baseline, every interviewee is assumed to be in a vulnerable position during questioning because of an inherent unequal power balance. On top of this baseline, some situational risk factors – such as being held in detention – may aggravate in particular a suspect’s inherent vulnerability. Furthermore, a number of individual risk factors may compound the baseline vulnerability.
Some of these individual factors create a heightened vulnerability precisely – or only – because of the situational context in which they manifest and/or because of the situation the interviewee finds oneself in. This is for instance true for factors related to culture and diversity. As such, Principle 3 acknowledges that vulnerability is not static. A person's circumstances can change during the course of interviewing. Vulnerability is rightfully approached as a dynamic and interactive phenomenon, because risk factors can arise or fluctuate depending on the context and culture at stake. This also implies that a heightened vulnerability can be more permanent, as well as temporary and may vary depending on the context and time. Many factors shaping a person's ability to participate in an interview arise before the formal interview starts. These may include the circumstances of arrest, the use of force, uncertainty about what is happening, sleep deprivation, substance withdrawal, emotional distress, prior trauma, or interactions with officials before arrival in custody.
Imagine two people with similar personal characteristics. One arrives at an interview after a calm and respectful arrest, adequate rest, and access to information. The other arrives after a stressful arrest, prolonged waiting, little sleep, and significant anxiety. Their ability to understand questions, exercise rights, and communicate effectively may differ substantially. This illustrates why vulnerability should be viewed as dynamic and contextual rather than fixed. It also shows that adjustments should not focus solely on individual characteristics. Sometimes the most effective response lies in modifying the environment, timing, or conditions of the interview itself.
Equally important is the emphasis on proactive identification and accommodation. Principle 3 encourages authorities to identify vulnerability before an interview takes place and to adopt measures that compensate for it, such as the presence of an interpreter, a support person, or a specially trained interviewer.
These ideas align closely with a preventive approach to torture and ill-treatment. Vulnerability should not become relevant only after problems arise. Instead, it should inform how interviews are planned, conducted, and evaluated from the outset.
From broad principle to practical challenge
Yet there is also a tension at the heart of Principle 3. A broad definition of vulnerability is attractive because it recognises human diversity and avoids reducing people to diagnostic labels. However, a concept that is too broad, including a variety of non-exhaustive and to some extent overlapping factors, can become difficult to operationalise.
During several discussions within the ImpleMéndez network1, practitioners and researchers seemed to welcome the breadth of the concept of vulnerability as how it is expressed in Principle 3, while simultaneously expressing uncertainty about its practical application. Important questions arise, such as when exactly should a person be considered to be in a situation of heightened vulnerability? Which factors matter most? How should different factors be weighed? What concrete measures should follow?
These questions matter of course, because adequately accommodating vulnerability implies that it should not merely remain a theoretical concept. Ideally, it should guide decisions on the ground. This is particularly important, because the challenge for practitioners is understanding when that vulnerability is heightened, how it manifests itself, and what should be done in response.
Other than acknowledging the importance of identifying vulnerability, the Méndez Principles do not elaborate on the identification of vulnerability. As the Méndez Principles are intended to inform law and policy, they do not provide specific guidance or specific examples on how vulnerability could be identified, nor information on specific screening tools and/or responses towards vulnerability.
In the absence of guidance and training, approaches of vulnerability in practice oftentimes rely heavily on lists of vulnerable groups or risk factors. Yet rigid lists carry risks of their own. They may become tick-box exercises, causing authorities to overlook vulnerabilities that are not explicitly listed. At the same time, categorising entire groups as vulnerable can unintentionally stigmatise individuals whose actual needs and capacities vary considerably.
The challenge is therefore not to identify "vulnerable people" but to identify situations in which a person's ability to participate effectively, exercise their rights, communicate accurately, or cope with the interview process may be compromised in a given situation. As such, one of the most promising aspects of recent discussions around vulnerability is the shift from categories to functions, moving beyond categories.
What does this mean for practitioners?
Implementing Principle 3 does not require perfect definitions or complex vulnerability scoring systems. Avoiding stigmatisation while remaining responsive to individual needs requires awareness, tailored responses and individual assessment rather than one-size-fits-all solutions. Meaningful progress in that regard can start with practical steps. First, identification should not be limited to a single screening moment. Vulnerability may emerge or intensify throughout detention and interviewing. Interviewers should therefore remain attentive to changing circumstances and needs.
Second, assessment should include factors preceding the interview, including detention conditions, fatigue, trauma (including recent or ongoing experiences), substance use, language barriers, neurodivergence and emotional distress.
Third, the key question is not whether someone belongs to a vulnerable group. It is whether they can effectively understand, participate, and exercise their rights at a given moment. Rather than asking whether someone belongs to a predefined vulnerable group, interviewers might ask questions such as:
have I provided the information in a way this person can understand?
Has the person understood it? Am I communicating in a way that allows the person to express themselves comfortably and accurately?
what adjustments are needed for the person to exercise their rights effectively?
are there factors affecting concentration, memory, decision-making, or emotional regulation and if so, how can I adequately address them?
are aspects of the environment increasing stress and if so, how can I accommodate this stress?
Fourth, practitioners may benefit from expanded training on vulnerability. Training should move beyond awareness-raising. Interviewers need practical guidance on recognising signs of vulnerability, adapting communication, working with lawyers, interpreters and support persons, and implementing trauma-informed approaches.
Lastly, jurisdictions can develop practical guidance linking common vulnerability-related challenges with possible responses, building a range of safeguards to adequately address vulnerability. These might, amongst others, include interview breaks, simplified communication, specialist support, environmental adaptations and specially trained interviewers. The objective should not be rigid rules, but informed decision-making.
A hopeful way forward
The Méndez Principles have already achieved something important: they have placed vulnerability at the centre of discussions about lawful, ethical, and effective interviewing. They intend to encourage policymakers, practitioners, and researchers from different disciplines to engage with a concept that is fundamental to both human rights protection and investigative practice.
The next step is implementation. This requires greater conceptual clarity, stronger training, and more practical guidance on identification and accommodation. It also requires recognising that vulnerability is not an exception affecting only a small number of people. It is inherent to the unequal balance of power at stake during interviewing and may become heightened through a wide range of personal and contextual factors. By approaching vulnerability as dynamic, contextual, and responsive to individual needs, practitioners can strengthen procedural fairness, improve the quality of information obtained, and ultimately contribute to the prevention of torture and other ill-treatment.
