What is investigative interviewing (and what is it not)? A primer on the ethos of suspect interviewing

Worldwide activities to implement investigative interviewing are steadily increasing (e.g. Walsh et al., 2024). Numerous academic articles and books also explore this approach to interviewing, particularly from a psychological perspective (e.g. Milne and Bull, 1999, in press). Nevertheless, there seems to be considerable confusion about what characterises investigative interviewing and how it contrasts with approaches designed to elicit confessions, such as those collectively referred to as as accusatorial interrogation (Meissner et al., 2014). Additionally, achieving a shift in organisational, cultural and methodological practices presents a significant challenge. This is problematic because misunderstandings and inaccuracies in defining the practical, psychological and legal foundations of investigative interviewing can lead to serious consequences, such as false decisions, wrongful convictions and other miscarriages of justice. Therefore, the aim of the present article is to characterise investigative interviewing for law enforcement leaders, researchers, analysts, decision makers and policymakers. In short, we define investigative interviewing as a practically applicable conversational approach to collect reliable and relevant information from suspects in a manner that encompasses actively open-minded thinking, evidence-based tactics and techniques and a legal and humane approach. Although these three core pillars of investigative interviewing also apply to approaches involving witnesses and victims, the focus here is on suspects, as errors in such interviews were the main reasons for extensive changes in countries such as the UK and Norway (e.g. Bull and Rachlew, 2020). After presenting an outline of the evolution of investigative interviewing, this article describes its three core pillars. We then address seven potential barriers to adopting it, derived from our international efforts at promoting it as researchers, trainers and practitioners. Finally, we argue that the introduction and implementation of investigative interviewing is possible both on individual and collective levels. While our main focus is on police interviews, this approach can also be applied to other types of information-gathering interactions, such as legal interviews conducted by prosecutors and judges.

The practice of questioning individuals about crime is as old as the act of prosecuting itself. Whether it is speaking with suspects, witnesses or victims, a fundamental skill that all interviewers must possess is effective communication. However, what constitutes “effective” questioning has been a matter of debate. Until the 1930s in the USA and elsewhere, the use of physical coercion was an accepted – and acceptable – practice used to extract confessions from suspects who were assumed to be reluctant (Leo, 2008). When physical force was deemed unlawful, psychological manipulation like trickery and deceit took its place in pursuit of the same goals (Kassin et al., 2010), and we know now that these practices have caused grave judicial errors. By the end of the 20th century, a slow-moving revolution in the way police interview suspects was underway, and in the time since, reforms have been spreading to different parts of the world (Barela et al., 2020) ^[1].

In the 1980s and 1990s, after a number of high-profile miscarriages of justice were linked to confession‐oriented interviewing techniques in England and Wales, new legislation and research paved the way for a transformation in interviewing (e.g. Baldwin, 1993; Bull and Cherryman, 1995; Moston et al., 1992). This shift entailed a fairer, more legal and scientifically based framework for interviewing all interviewees, whether they were witnesses, victims or suspects. The aim of the interview then became more clearly focused on the gathering of accurate and fulsome information about the matters under investigation (e.g. Bull, 2002; Kebbell and Milne, 2022; Milne et al., 2019). The investigative interviewing ethos was first expressed within the PEACE model of interviewing (Williamson, 1993), which was implemented as a practical and effective alternative across the UK by all police forces (regions) in the early 1990s (e.g. Akca et al., 2022; Bull and Milne, 2020; Cherryman and Bull, 2001; Clarke and Milne, 2001; Goodman-Delahunty and Martschuk, 2018; Griffiths and Milne, 2006; Walsh and Bull, 2010). PEACE was the acronym chosen by the police officers developing the method for the five stages involved: planning and preparation, engage and explain, account, closure and evaluation.

The investigative interviewing approach has been subsequently adopted in other countries (e.g. Australia, Ireland, New Zealand, Norway, Singapore and Sweden), mainly as a consequence of errors of justice linked to coercive and suggestive interviews (e.g. Fahsing and Rachlew, 2009; Chin et al., 2022). In 2019, investigative interviewing was recommended as the preferred approach for all European countries by the Council of Europe’s Committee against Torture and Other Inhumane Treatment (European Committee for the Prevention of Torture and Inhuman or Degrading Treatment or Punishment, 2019).

A central marker capturing the shift in mindset towards the best way to gather accurate and reliable information from individuals as part of investigations or intelligence-gathering operations is the expert-led document released in 2021, the “Principles on Effective Interviewing for Investigations and Information Gathering” – also known as the Méndez Principles ^[2]. The principles aim to improve interview quality while safeguarding the human rights of interviewees by providing an overview of what is termed effective interviewing. There have been many important developments in systematic study regarding what is most effective (e.g. Catlin et al., 2024), and the Méndez Principles are meant to establish international standards for interviews based on this research, the applicable legal safeguards along with ethical principles.

Following the publication of the Méndez Principles, more than 50 UN Member States have expressed joint support for it (e.g. in October 2022, UN Member States expressed their support ^[3]). Furthermore, in 2024, the United Nations Department of Peace Operations, Office of the High Commissioner for Human Rights and Office on Drugs and Crime approved another document that outlines the practical steps to implement the Méndez Principles in a policing context, “The Manual on Investigative Interviewing for Criminal Investigation”. The ethos of “investigative interviewing” has been progressing for decades in various jurisdictions and has been the basis for important contributions to each of these texts – it is one highly-developed form of effective interviewing ^[4].

Promoted by forward-thinking police leaders and policymakers and supported by academic research, investigative interviewing continues to gain momentum (Walsh et al., 2024). As a result, it is expected to be increasingly implemented and highlighted in guidelines, training and police and legal practice around the world. However, misconceptions and inaccuracies in the definition and interpretation of its practical, psychological and legal foundations can lead to serious consequences in the administration of justice. For example, the so-called Reid Technique (Inbau et al., 2013), which is characterised by a primary focus on obtaining confessions, has been found to be scientifically ineffective (e.g. Gudjonsson, 2003; Kassin, 1997; Kassin et al., 2010). The Reid Technique’s central tactics are accusatorial and psychologically manipulative, and research has found that these raise the risk of obtaining unreliable information and false confessions (e.g. Russano et al., 2005). However, John E. Reid & Associates, Inc., has recently begun providing courses entitled “The Reid Technique of Investigative Interviewing and Advanced Interrogation Techniques” ^[5] or “The Reid Technique of Investigative Interviewing and Positive Persuasion” ^[6]. Descriptions of the course content – such as the “Behaviour Analysis Interview” or “the Reid nine steps of interrogation”, two hallmarks of accusatorial interrogation – suggest no fundamental changes in the approach over the years. In general, the Reid Technique stands in stark contrast to the evidence-based and practical proven ethos of investigative interviewing (Catlin et al., 2024; Meissner et al., 2014, 2017). Following this, such rebranding can lead to confusion and a false impression of the extent to which the Reid Technique follows the basic ideas of investigative interviewing. Therefore, the intention of this primer is to introduce law enforcement leaders, researchers, analysts, decision makers and policymakers to what this practice is – and, importantly, what it is not. For this purpose, this paper identifies and describes the three core pillars of investigative interviewing from our experience and insights as researchers, trainers and practitioners.

The reason why interviewers behave in an accusatory manner can often be found in the overall investigations and the interviewers’ mindset. The success of criminal investigations depends to a great extent on investigators’ abilities to make sound and fair decisions (e.g. Ask and Alison, 2010; Ask and Fahsing, 2019). However, investigators face several obstacles to optimal decision-making (e.g. Ask and Granhag, 2007; Stelfox and Pease, 2005). A striking parallel identified across numerous high-profile investigative failures worldwide is that investigators strive to confirm their initial assumption about the case (e.g. Fahsing, 2016; van Koppen, 2008). More specifically, in such cases investigators typically search, select and interpret information in line with their initial suspicion, while they seemingly ignore alternative interpretations and often neglect their duty of also searching for potentially disconfirming information. Such biased processing, which often takes place unconsciously, is referred to as confirmation bias (e.g. Ask and Granhag, 2005; Nickerson, 1998).

Interviewers who implement such confirmatory thinking typically use accusatorial and manipulative tactics to gain information that supports their initial suspicion. For example, they might (a) manipulate the suspects by minimising the seriousness of the accusation and pretending to be a helpful friend by being sympathetic, (b) leading the course of the interview in a suggestive manner by ignoring denials, repeating questions or providing case-related information, or (c) coercing the suspects by interrupting them during their statements, being dominant or threatening, overstating the evidence or even lying about existing evidence or maximising the consequences of non-cooperation or denial. Also, such an approach may be undergirded by the reliance on non-verbal cues to detect deception, and interviewers who are operating with a confirmatory mindset will tend to see lies in behavioural indicators that have no diagnostic value.

The risks and problems of confirmatory thinking are multi-layered. Firstly, it increases the use of confession-oriented tactics that seek incriminating information and confessions instead of reliable and accurate information, thereby multiplying the risk of eliciting unreliable information (e.g. Gudjonsson, 2003; Horgan et al., 2012; Russano et al., 2005). Secondly, confirmatory thinking interviewers and investigating officers can mistakenly perceive such information as subjectively correct because it confirms their initial suspicions, assumptions and expectations (e.g. Narchet et al., 2011), and thus relevant information can remain unpursued or unnoticed. Thirdly, unreliable and false information increases the risk of false decisions and wrongful convictions (e.g. Kassin et al., 2013), which not only harms innocent persons but also keeps our societies unsafe because the real offenders are still out there.

Therefore, interviewers should avoid assumptions of guilt, confirmatory thinking and an accusatorial interview style by adopting actively open-minded thinking. This term is based on Baron’s (2019) work within the political context, and he describes how actively open-minded thinking helps citizens with problem-solving, resistance to common biases and overconfidence. Actively open-minded thinking is characterised by seeking information that may support or contradict pre-existing hypotheses, including an openness to change minds in the face of new information (Kahneman et al., 2021). In criminal investigations keeping an open mind is not something that happens naturally or a competence that comes with the badge. Paradoxically, if we were to survey interviewers, many or most would probably say that they conduct all interviews with an open mind because they want to find out what happened and do not want to prosecute innocent people. However, individual case studies and the mechanisms of confirmation bias outlined above illustrate that biased processes are deeply embedded in human cognition, can undermine fair investigative decision-making, and it is not sufficient to simply assume that this is done in an open-minded manner. This is not because interviewers are corrupt or lazy. The human mind uses heuristics, makes error-prone decisions and tends to jump to conclusions (e.g. Kahneman, 2011; Kahneman et al., 2021). Therefore, it is essential that interviewers understand their naturally strongly biased outset and actively strive for open-minded thinking to make sound and fair investigative decisions.

Similar to implicit racial bias training (Forscher et al., 2017), one way to avoid a confirmatory mindset is to learn about its existence and consequences and to recognise that even experts are not immune to it and cannot overcome it through sheer willpower alone (e.g. Dror, 2020). Furthermore, in line with general recommendations for judgements (e.g. Arkes, 2001), actively and deliberately identifying and documenting alternative explanations to the initial suspicion is likely the best way to foster actively open-minded thinking during criminal investigations. This might promote an investigative-mindset and protect investigators from confirmatory thinking (College of Policing, 2021; Fahsing, 2016). Furthermore, formulating alternative hypotheses (e.g. on the creation and meaning of case-related information) can assist investigators towards a more balanced collection of relevant and reliable information. In our interviewing trainings and when advising in real-life cases, we have found it helpful to divide the development of an actively open-minded interview strategy into four basic steps: firstly, after reviewing the available information in the case – interviewers should formulate all reasonable alternative hypotheses (e.g. Fahsing et al., 2021). Secondly, they should identify information gaps in the hypotheses that could be addressed in interviews. Thirdly, based on the formulated hypotheses and information gaps, interviewers should determine relevant invitations/questions to use in the interview (e.g. Hartwig and Granhag, 2023). Fourthly, interviewers should plan if, when and how to present the available evidence (e.g. Luke and Granhag, 2023; May et al., 2017; Nyström et al., 2024) while considering all legal requirements (Sukumar et al., 2016). Doing so might help make interviews more relevant, accurate and fair. Furthermore, an active and explorative use of alternative hypotheses in the interview might reduce the chances of guilty suspects offering false explanations (e.g. a fabricated alibi) later in the investigation or in court (so-called tailoring of evidence).

Many organisations that make individual care or service delivery decisions have adopted evidence-based practices (e.g. substance abuse treatment and surgical techniques). In general, evidence-based practices are characterised by broadly accepted research findings instead of practices based solely on anecdotes, myths, intuition or personal experiences. In line with this, law enforcement services and activities are also (increasingly) adopting evidence-based practices (Lum and Koper, 2024).

For interviews, law enforcement has long relied on so-called “tribal knowledge” to reach their goals. These kinds of techniques and tactics are passed down from generation to generation of police through informal, on-the-job training that is primarily based on the experience of the more senior officer and their perception of what is “effective” (Leo, 2008). However, several conditions must be met to be considered an evidence-based interviewing technique. Firstly, and perhaps most importantly, the technique must be subjected to independent evaluation. In other words, the interviewers who use the technique are not the same individuals who assess its effectiveness, even if the practitioners should invariably be consulted before, during and after any such evaluation. Independence of this kind is critical to the entire endeavour of producing valid scientific knowledge, but police practitioners are not usually skilled in research methods, just as researchers are not typically skilled at conducting investigative interviews. Secondly, the evaluation must demonstrate effectiveness at producing desired outcomes in a scientifically clean and robust setting, such as gathering accurate and reliable information (Kelly and Russano, 2023). Finally, for any technique to be deemed truly evidence-based, it must undergo repeated independent evaluations, ideally using different methodologies, settings and samples, and conducted by separate teams of researchers (e.g. Kelly et al., 2024). The replicability of behavioural science findings has sometimes been difficult to accomplish (Pashler and Harris, 2012), but that does not mean that replication should not be attempted, with recommendations for adjusting practice based on the convergence or divergence of results. A related process was put forth by Meissner and colleagues (2017) that incorporated both highly controlled experiments conducted in the laboratory and naturalistic studies from the field that observe and evaluate the techniques in practice, thereby increasing the ecological validity criticism that is sometimes levelled at interviewing research conducted in laboratory settings. When the results from these different methodologies converge, researchers and practitioners can be confident in referring to the techniques as evidence-based.

An example from the literature that demonstrates both the effectiveness of an interview approach and that has been replicated across many settings are the questions and invitations used in interviews. In general, open-ended questions/invitations yield more reliable information than specific/closed or leading questions (e.g. Boon et al., 2020; Ceci and Bruck, 1993; Lamb et al., 2008; Milne and Powell, 2010; Wilson and Powell, 2001). Leading questions should be avoided as they suggest desired answers, which may contaminate the suspects’ account by introducing details that were previously unknown to the suspects.

Rapport is another research-based element that has been repeatedly shown to be effective across settings and samples in interviews. It starts at the first contact with the suspects and needs to be maintained during the whole interaction (e.g. Alison and Alison, 2017; Alison et al., 2021). It has been found important that interviewers accept the autonomy of suspects and show respect to treat the interviewee as a human being. Achieving genuine mutual respect and trust is key to establishing and maintaining rapport across the interaction (e.g. Nunan et al., 2020; Walsh and Bull, 2012). Research has shown that the level of rapport established is directly linked to the amount of investigative relevant detail obtained in real-world interactions (e.g. Alison et al., 2021; Baker-Eck and Bull, 2022). Overall, evidence-based interviewing techniques, tactics and elements have been demonstrated to improve interviewers’ ability to elicit accurate information, including reliable admissions and confessions.

Investigative interviewing has an ethos to gather information in a manner that is legal and humane. This involves acting without coercion or prejudice, and to some degree, the term “legal and humane” might seem obvious to some. However, the available literature indicates that it is quite common among interviewers to think that they can bend the law to obtain what they themselves think of as the proper results (Reiner, 2010; Skolnick and Fyfe, 1993). As described by Leo (2008), it is too often the case that for detectives, the ultimate goal is to make the suspects accept and adhere to the theory of guilt – to make them confess. This outsmarting game is “structured to promote incrimination, if necessary, over truth-finding” (p. 23). We argue that such practices are unethical and can lead to actions that fall outside the law. Interviewers play a crucial role in upholding the rule of law and safeguarding the rights of individuals during criminal investigations. To prevent abuses of power, ensure fairness and impartiality and maintain the integrity of the criminal justice system, interviewers are bound by a set of fundamental laws and international conventions. Here are five of the minimum rights:

The absolute prohibition of torture is binding on all states and is applicable in all circumstances; no exceptions can be made for emergency, geography or any other reason [e.g. International Covenant on Civil and Political Rights (ICCPR), 1966, art. 7; Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment (CAT), 1984, arts. 1–2; Geneva Convention, 1949a, 1949b, 1949c, 1949d, Common art. 3; for discussions, see Nowak and McArthur, 2008; Rodley and Pollard, 2009). While torture may seem distant or irrelevant to some jurisdictions, less severe forms of ill-treatment are also strictly banned (cruel, inhuman and degrading treatment). Such methods can subtly seep into everyday practices to affect the way interviewees are treated. Even without direct intent, practices that violate human dignity – excessive pressure, humiliation or coercion – can arise and are no less forbidden [Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment (CAT), 1984, art. 16]. Moreover, the accumulation or pattern of mistreatment can escalate into conditions that are tantamount to torture. Legal frameworks stress the importance of respecting the dignity and rights of suspects during arrest and that any information or statements obtained by mistreatment are inadmissible in court proceedings [Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment (CAT), 1984, art. 15]. The extensive regulatory structure demonstrates that not only are interviewers obliged to comply but also the societies they serve have codified these shared values as an unbreakable rule.

The law mandates that suspects and accused persons are considered to be innocent until a court of law determines that they are guilty of a crime [International Covenant on Civil and Political Rights (ICCPR), 1966, art. 14(2); United Nations General Assembly, 2015, Rule 111; United Nations General Assembly, 1988, Principle 36). Interviewers must treat suspects with respect and dignity, and any statements made by suspects should be evaluated objectively and without bias.

Suspects have the right to remain silent and refuse to answer any questions during an interview – a right inherent in the presumption of innocence. Moreover, although the consequences of exercising this right vary across countries, it is clear in international law that no person can be compelled to confess guilt or testify against oneself [ICCPR, 1966, art. 14(3)(g)]. And in certain jurisdictions, interviewers must clearly inform and respect suspects of their right to silence before questioning begins. As such, this right is essential to prevent coerced confessions and protect individuals from forced self-incrimination; silence should have no bearing on any eventual court decision of guilt or innocence [e.g. Rome Statute of the International Criminal Court, 1998, art. 55(1)(a), 55(2)(b)]. The legal conclusions drawn from silence depend on the weight attached to those inferences by national courts when assessing the evidence, the circumstances of the case, particularly the situations in which inferences may be made, and the degree of compulsion inherent in the situation (Murray v. United Kingdom, 1996), but should never be used as a means of pressure.

All persons arrested or detained have the right to a lawyer, including through legal aid, from the outset of their deprivation of liberty [International Covenant on Civil and Political Rights (ICCPR), 1966, art. 14(3)(d); United Nations General Assembly, 1988, Principle 17]. This means interviewers must inform suspects of their right to legal counsel without delay, and provide them with a reasonable opportunity to consult with an attorney before talks. In many jurisdictions, this right includes the presence of a lawyer during the interview process. Access to legal counsel is inextricably linked to the protection of rights, the prevention of ill-treatment and guidance through a complicated process that can result in significant, life-changing outcomes.

State agents must ensure that interviewees are treated without any adverse distinction or discrimination [International Covenant on Civil and Political Rights (ICCPR), 1966, art. 2(1)]. In the interview setting, there are a number of factors that can place an individual in a heightened situation of vulnerability: e.g. age, language, gender, nationality or ethnicity, cultural or religious background or psychosocial disabilities. Interviewers must assess and address any vulnerabilities of the interviewee and specialised procedures or accommodations may be required to give such persons equal access to justice. For example, proper training of police personnel may be required to serve a particular community or expedited access to translators and specialists may be needed.

If interviewers do not follow the legal requirements of criminal justice, they compromise the very foundations of the rule of law and fair trials. Interviewers who break the law compound the problem of the crimes they are trying to fight. As stated by US Supreme Court Chief Justice Earl Warren, writing for the majority in Spano v. New York, 360 U.S. 315 (1959, pp. 320–321): “The abhorrence of society to the use of involuntary confessions does not turn alone on their inherent untrustworthiness. It also turns on the deep-rooted feeling that the police must obey the law while enforcing the law; that, in the end, life and liberty can be as much endangered from illegal methods used to convict those thought to be criminals as from the actual criminals themselves”.

The three pillars of investigative interviewing – (i) actively open-minded thinking, (ii) research-based tactics and techniques and (iii) a legal and humane approach – are designed to work in harmony. However, conflicts may arise between these pillars. One example is the fact that certain aspects of interviews are underexplored (e.g. due to the complexity of human interactions and cultural differences). Until further research addresses these gaps, interviews should adhere to the pillars of actively open-minded thinking and a legal and humane approach on these aspects. Notably, actively open-minded thinking is directly connected to the fundamental principles of a fair trial, particularly the principle of the Presumption of Innocence [International Covenant on Civil and Political Rights (ICCPR), 1966, art. 14(2)]. For another example of a conflict between the pillars, let us imagine a hypothetical scenario where robust research develops a tactic aimed at persuading suspects to abandon a previously declared intent to exercise their right to silence during a police interview. Firstly, it is important to note that the research would also need to show this action is beneficial to evoking accurate information to be considered relevant; getting someone to speak is not the ultimate goal. Moreover, such a tactic would conflict with the Right to Silence [International Covenant on Civil and Political Rights (ICCPR), 1966, art. 14(3)(g)]. In such cases, the pillar of conducting interviews in a legal and humane manner must take precedence. This prioritisation underscores the fact that investigative interviewing remains firmly anchored in law, ensuring that all adaptations respect fundamental human rights.

The pillars described above are all supported by sound psychological and legal research. They are all mutually reinforcing and we argue that ignoring just one of these will negate the holistic idea of investigative interviewing and with it, any attempt to implement it. Nevertheless, some of these elements are sometimes neglected by policymakers, law enforcement decision makers and trainers during the introduction of the reforms and by practitioners during their implementation, whether consciously or unconsciously. Below, we discuss seven arguments that aim to limit the value of investigative interviewing. They are based on our personal experiences in advisory meetings, training, research and insights from real interviews.

Practitioners sometimes argue that it is their job to motivate suspects to make a statement, often by suggesting it is in their interest to waive their right to remain silent. We argue that this contradicts the accuser’s burden of proof, the protection against self-incrimination and the suspects’ right to remain silent. Attempting to convince suspects to talk or confess, even through informal conversations or pre-interviews, therefore compromises the suspects’ rights. The open-minded interviewer is equally interested in both inculpatory and exculpatory information. Nonetheless, seeking to motivate suspects to waive their right to remain silent and make a statement can frequently be observed in confession-oriented interviews and thus can indicate confirmatory thinking. For example, in such cases, the process can commonly involve a fluid transition from encouraging the suspect to make a statement – to then challenging that statement, using both subtle and direct manipulation to ultimately obtain a confession. This means that even if there were science-based ways to get suspects to waive their right to remain silent, they should not be used, as they indicate confirmatory thinking and can be unlawful.

Practitioners sometimes argue that investigative interviewing is suitable for witnesses but not for suspects. They further argue that sometimes harsher, closed questions, direct accusations of guilt, trickery or using non-verbal cues to detect deceit are necessary for suspects. However, such confession-oriented tactics increase the risk of obtaining inaccurate information, false confessions and subsequent false decisions and wrongful convictions, and are, generally speaking, not evidence-based. Furthermore, they are an expression of confirmatory thinking. If the assumption of the suspect’s guilt is factually founded, there should be enough evidence without the suspect’s statement. If this is not the case and there are information gaps and possible alternative interpretations, more reliable information is needed. Therefore, the goal of investigative interviewing is to gather reliable and relevant information from witnesses, victims and suspects. Since basic psychological mechanisms like human memory, thinking and decision-making do not differ between witnesses and suspects and are rather rooted in the general human nature, investigative interviewing should not distinguish between suspects and witnesses, especially as often the best witness to a crime is the person who committed it (Bull, 2019). (However, differences are made in the rights that differentiate between suspects and witnesses. Thus, essential differences are only made in terms of the legal roles.)

Some practitioners and trainers with practical experience argue that while investigative interviewing often achieves its goals of solving crimes, sometimes other techniques are needed, usually to obtain a confession. This can result in a toolbox of evidence-based practices of investigative interviewing combined with confession-oriented tactics (see also Snook et al., 2020). Such an argument and approach are not in line with the core pillars of investigative interviewing. Any use of confession-orientated tactics is not scientifically justified, should be seen as an expression of confirmatory thinking and can result in unlawful action as it conflicts with the presumption of innocence.

Many practitioners, trainers and researchers say that the most important part of an interview is to build and maintain rapport with suspects. In this context, it should be noted that there are different views on what rapport actually is. Some explain that the aim is to establish a relationship with suspects so that they make a statement – any statement. This might include interviewers pointing out the advantages for the suspects to speak, downplaying the consequences of an incriminating statement and generally being friendly and sometimes even chummy (all elements of confession-oriented tactics that increase the risk of unreliable information and false confessions). Such a response demonstrates how rapport-building can actually be turned into manipulation to pursue one’s own “interests”. However, it should not be forgotten that the interest of the interviewers is fundamentally to gather factual information – not a conviction, and certainly not a wrongful conviction. It should also be noted that this would indeed violate the right of the suspects to freely decide whether or not to make a statement. Moreover, such manipulative procedures are not effective and contradict the pillar of an actively open-minded thinking. Nevertheless, rapport can indeed be in line with the pillars presented above, as described, for example, by Alison et al. (2021): “rapport can broadly be considered the relationship established between the interviewer and interviewee throughout the course of their interaction, based on trust, empathy and a shared understanding of one another, where it is incumbent on the interviewer to make the effort to remain open-minded and curious rather than judgemental” (p. 34).

Some argue that planning an interview strategy, then creating rapport and then collecting a free report takes too long for daily work, making investigative interviewing suitable only for serious crimes. In line with this, rapidly collecting information might seem useful at the outset. However, it must not be forgotten that this creates false leads, a waste of resources and potentially false decisions and miscarriages of justice. Moreover, there is no utility in allowing someone who has committed a crime to remain free to become a repeat offender. Countries such as the UK and Norway use investigative interviewing for all types of crimes (Rachlew and Fahsing, 2015; Milne and Bull, in press). Conversely, every citizen should be entitled to be interviewed using the most effective technique that respect their rights.

Some practitioners argue that confession-oriented tactics that include, for example, manipulation, accusation or coercion are helpful and should be used unless they are actually prohibited by a court. This view is problematic because, for example, subtle manipulation (such as indirectly raising the possibility of a mitigated sentence) does not directly contradict legal requirements. However, as outlined previously, there are studies that show that confession-oriented tactics are not effective when aiming to collect reliable information (Catlin et al., 2024; Meissner et al., 2014). Furthermore, we argue, based on numerous case studies and research, that such tactics assume the guilt of the suspects (and are not an actively open-minded thinking). This means that even if there are no national laws prohibiting such practices, they contradict the presumption of innocence. Finally, there is research indicating that legal professionals may find it difficult to adequately assess confessions due to a lack of expertise (Schneider et al., 2024). Accordingly, every person involved in an investigation and criminal proceedings should do their best to improve the quality of decisions.

Some practitioners, trainers, decision makers and policymakers argue that special training and/or recording technology – both being central components of investigative interviewing – is too expensive. However, recording devices are affordable, and associated costs like storage and transcription need creative solutions. Training costs are mainly for logistics, not the technique itself. Well-founded training can reduce investigation costs and increase officers’ well-being (Giles et al., 2021). It seems therefore wise to consider the future benefits and not just the immediate costs when making cost-benefit calculations.

Legislative and procedural changes in countries such as the UK and Norway were initiated after recognising severe miscarriages of justice linked to poor police interviewing of suspects. In the UK, these changes were politically driven, while in Norway, the police themselves initiated them (Fahsing and Rachlew, 2009). Miscarriages of justice are viewed as the “single most influential driver of change within the system” (Griffith and Milne, 2018, p. 271). Human factors like limited investigative thinking and decision-making are common sources of error in interviews and criminal investigations. These factors, including culture, politics and organisational group-think, often overshadow the application of effective interviewing knowledge. We, therefore, argue that adherence to the three core pillars of investigative interviewing helps to improve the quality of interviews and investigations and can also lead to an increase in citizens’ trust in law enforcement – or police legitimacy (a willingness to engage or cooperate). In this article, we have developed the three pillars that should be applied when introducing and implementing the ethos of investigative interviewing: (1) actively open-minded thinking; (2) research-based tactics and techniques; and (3) a legal and humane approach.

However, implementing changes in interviewing procedures requires a collaborative effort from various parties – both inside and outside of the law enforcement service. There are several elements that have been found to be fruitful in implementing these core pillars of investigative interviewing in police training and practice. Interviewers should electronically record the interview, structure it with a phased approach (e.g. PEACE), use productive questions/invitations while using active listening and adopt an open interview strategy. In general, we view electronically recording as a minimum requirement for professional interviews because it comes with many benefits. In the case electronic recording is not possible, other elements of the investigative interview – such as structuring, using productive questions or an open interview strategy – can still be implemented. In turn, an electronic recording is of little use in court without the expertise on how to evaluate the interview practice. Therefore, experts should be consulted to assess the recording and/or (independent) legal practitioners be trained to be able to evaluate the interviews. This means that these recommendations also apply to other legal and forensic interviewers, such as judges, prosecutors and psychologists, depending on the legal system who need to conduct and/or assess interviews.

Trainers should rely on scientific evidence and proven techniques when designing curricula and training sessions and have been trained themselves. They should also consult research on training methodology, which is an increasingly expanding field (e.g. Haginoya et al., 2023; Powell et al., 2016, 2022). We noted that renaming the training on the Reid Technique by including the term investigative interviewing can lead to a false connection. We encourage trainers to critically examine the content of any training with respect to the three core pillars of investigative interviewing. Furthermore, they should carefully check the extent to which techniques and tactics are actually evidence/science-based, and this research basis is not only suggested by the title of the publisher (e.g. professor) or non-peer-reviewed articles (e.g. internal documents or master theses). For example, in Germany, some (police) books and manuals contain descriptions of tactics that are not scientifically based and are rather confession-orientated, but which were probably taught in police training – at least until recently (for discussion, see May et al., 2022; Schneider and May, 2021).

Researchers should partner with practitioners, trainers and decision makers to identify research needs, examine barriers and limitations of investigative interviewing and possible solutions. In doing so, they should also take legal obligations into account and not simply fulfil “requests” of practitioners and lecturers (e.g. by developing tactics to motivate suspects to waive their right to remain silent). Policymakers and decision makers need to create an environment for change that supports practitioners, trainers and researchers in optimising investigative interviewing by implementing productive legislative frameworks, promoting a learning culture and supporting research-based evaluations (Griffith and Milne, 2018). In conclusion, it is time for practitioners, trainers, researchers, decision makers and policymakers worldwide to collaborate in implementing the standards established by a growing number of institutional organisations — exemplified by initiatives such as ImpleMéndez (COST Action 22128). The Méndez Principles on effective interviewing set a newly developing standard and the investigative interviewing ethos help move this important work forward.

The authors sincerely thank Andy Smith, National Interview Adviser at the National Crime Agency, for his valuable feedback on their manuscript.

Funding: This article is based upon work from COST Action ImpleMéndez (CA 22128) supported by COST (European Cooperation in Science and Technology, www.cost.eu). The publication was funded by the Open Access budget of Medical School Berlin.