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But does it work?

Another critical look at the science of training in investigative interviewing.

Builds on the ideas from "Evidence- based investigative interviewing" (Jan 6, 2021) and critically assesses the existing evidence-base for investigative interviewing.

“The test of any police procedure”

In the preface to the very first interrogation manual, Kidd (1940; p.vii), stated that “The test of any police procedure is: Does it work ?” It is difficult to disagree with such an intuitive standard, but while the question may be simple, the answers are often altogether more complicated.

Ever since the birth of modern policing there has been a clear recognition that determining whether or not something has worked may be difficult. For example, Sir Robert Peel (1829) outlined a series of principles to guide the development of the fledgling police service. Principle 7 states: “The test of police efficiency is the absence of crime and disorder, not the visible evidence of police action in dealing with them” (p.1; my italics). Assessing the absence of something is only possible if you have a clear idea of how often it occurs (a system of measurement) and that you are then able to apply that same system of measurement at a later time (replication).

This core problem underpins attempts to determine whether police interviews with suspects have improved since the introduction of the PEACE model of interviewing. Whilst we have a considerable body of (largely) anecdotal evidence of police interviewing practices pre-PEACE (in the UK at least), that body of knowledge (e.g., Baldwin, 1993; Moston & Engelberg, 1993) does not constitute a clear baseline from which to judge any subsequent changes. Researchers attempting to demonstrate changes historical-to-present must co-opt those earlier findings to establish their argument (e.g., Soukara et al., 2002). In countries without any pre-PEACE data (e.g., Australia), such comparisons are inherently impossible.

To further complicate matters, even if historical reference data could be obtained, it would be highly speculative to infer that any improvements in current practice can be attributed to a single factor, such as the rollout of new interview training. Changes in the use of technology (e.g., mandatory video recording of interviews in the police station, the use of body-worn cameras outside the police station), as well as legislative changes, and an increased awareness of miscarriages of justice, might also be potential causes of changes in interviewing practice.

Does PEACE work?

Attempting to determine whether the PEACE model of interviewing works would appear to be a rather pointless exercise. The clear consensus is that that it does, and that it is both scientific and ethical. Here are some typical examples of that consensus:

  • “The scientifically grounded PEACE model has been advanced as a foundation for a standardised national model to replace the current accusatorial approach” (Vanderhallen & Vervaeke, 2014; p.67)

  • “It is generally accepted that the implementation of the PEACE framework has enhanced interviewing skills” (Walsh & Bull, 2015; p.661)

  • “The effectiveness of the PEACE model has been researched extensively, the results of which have informed the very nature of investigative practice” (O'Neill & Jones, 2019; p.251)

  • “….research has demonstrated that the PEACE interview model is effective with victims, witnesses, and suspects” (Howes, 2020; p.333)

The consensus is thus clear: PEACE works. Unfortunately, however, a close examination of the evidence-base for that consensus reveals an altogether different story.

To begin, it should be pointed out that there are two main parts to PEACE: the cognitive interview, primarily used for interviews with witnesses, and conversation management, primarily used for interviews with suspects.

There is an extensive body of research demonstrating that the cognitive interview does indeed work (e.g., Fisher et al., 1989; Geiselman et al., 1985; Satin & Fisher, 2019), though there remain some doubts as to whether police officers use the technique consistently or correctly (see Dando et al., 2009; Wheatcroft et al., 2014). Nevertheless, it would be reasonable to describe the cognitive interview as scientifically grounded. It would also be reasonable to say that it is ethically sound.

Conversation management was initially a component of the “ethical interviewing” model advocated by Eric Shepherd (1991). Shepherd’s approach to interviewing was, from the outset, positioned as an alternative to coercive (unethical) interviewing, and consequently its ethical credentials are clear (for example, see the total rejection of the legitimacy of "persuasive questioning" in the conclusion to Shepherd, 1993). However, its scientific credentials are not so clear.

Setting aside studies on the limited utility of conversation management to interviews with witnesses (studies show it is counter-productive, see Clifford & George, 1996), there are remarkably few papers centring on the conversation management approach, and each of those is restricted to describing the approach, not whether or not it works (e.g., Shepherd, 1993; Shepherd & Kite, 1988, 1989). None of these descriptive accounts were published in peer reviewed journals and many are now very hard to locate. Subsequent books by Shepherd on the conversation management approach (Shepherd, 2007; Shepherd & Griffiths, 2013) have followed the same description-only pathway, meaning that Shepherd offers no evidence base to show that conversation management works. Subsequent authors have adopted the same non-critical path. For example, in the book Investigative interviewing by Milne and Bull (1999), the absence of research on the efficacy of conversation management is only briefly (one paragraph) acknowledged, approximately 100 pages (see p.187) after devoting an entire chapter to describing the procedure.

Unfortunately, matters only get worse. It is extremely doubtful whether some authors have read any of the primary accounts of the technique. Instead, many cite the summary of the approach included in Milne and Bull (1999). That description is of limited value as it describes components of the conversation management approach that few (if any) current police trainers or officers are using, specifically, SE3R and GEMAC.

It is both illogical and inappropriate to cite evidence for the cognitive interview as proof of the overall PEACE model. That evidence only validates one part of the PEACE model. Scientific proof is not established by association (e.g., astronomy is scientific, astronomy is not). Those who argue for the conversation management technique can only do so on the belief that it is effective, not because of any evidence base. If so, then where does that belief come from?

Evidence-based training in interviewing

Early indications that PEACE worked were encouraging. The first study of training, conducted by McGurk et al. (1993), found that PEACE-trained officers were more knowledgeable than untrained officers, and that they conducted better interviews with both witnesses and suspects,. However, subsequent internal reviews (largely unpublished) by police officers soon began to suggest that training was not as effective as the first review had suggested.

In 2001 Clarke and Milne submitted a second evaluation of PEACE training and their conclusion was not so positive. PEACE-trained officers conducted longer interviews than untrained officers, but apart from that there was little evidence of any improvement in interviewing (relative to pre-PEACE research) and little evidence that training was having any positive effect. In fact, trained officers were more likely to use negative interview techniques such as overtalking, leading questions and statements. Clarke and Milne suggested that officers were being asked to learn too much on PEACE courses and that a tiered approach to training (depending on operational needs) would improve matters. That suggestion resulted in the five-tier model of interview training now in place in the UK. At that point our story comes to a very premature end.

Since the publication of that second review in 2001 there has not been any new evaluation data on the efficacy of PEACE training on police officers. There have been studies of the efficacy of PEACE-training in other contexts, such as with benefits fraud investigators (e.g., Walsh & Bull, 2010; Walsh & Milne, 2008), largely showing only limited benefits to PEACE training on operational practice. This appears to be because the courses contain too much content, the trained officers regress to previous habits, or possibly because there is a lack of supervisory oversight. There have also been studies showing that Australian police recruits adhere to the content of training (e.g., Tudor-Owen et al., 2016). But there hasn’t been a full evaluation of PEACE training for the interviewing of suspects by police officers for two decades.

Instead, advocates of PEACE rely on the findings of studies that featured ideas similar to those included in PEACE as evidence that the procedure has a scientific basis. It is worth noting that Reid Associates employ exactly the same strategy (sometimes citing the same studies) to justify the “science” underpinning their procedures (see The problem here is that studies showing the efficacy of a technique, such as building rapport, do not prove that the version of rapport building in PEACE is effective. Instead, such a study shows that some version of rapport is beneficial in some circumstances. The evidence base lacks specificity.

Despite this lack of an evidence base, trainers in countries such as Australia are adapting the PEACE model (often with little to no oversight concerning those adaptations) and the model continues to be adopted (and further adapted) worldwide. This begs the questions: why? If interviewing practice is to improve an evidence base of what works is required. The twenty-year gap in research is simply inexcusable. PEACE was initially created following a breakdown in public confidence in policing, history may need to repeat before police services decide to act and to evaluate this important part of their training. Prevention, as they say, is always better than the cure.

Dr Stephen Moston


Baldwin, J. (1993). Police interview techniques: Establishing truth or proof? British Journal of Criminology, 33(3), 325-352. Clarke, C., & Milne, R. (2001). National evaluation of the PEACE Investigative interviewing course. Home Office. Clifford, B. R., & George, R. (1996). A field evaluation of training in three methods of witness/victim investigative interviewing. Psychology, Crime & Law, 2(3), 231-248. Dando, C., Wilcock, R., Milne, R., & Henry, L. (2009). A modified cognitive interview procedure for frontline police investigators. Applied Cognitive Psychology, 23(5), 698-716. Fisher, R. P., Geiselman, R. E., & Amador, M. (1989). Field test of the cognitive interview: Enhancing the recollection of the actual victims and witnesses of crime. Journal of Applied Psychology, 74(5), 722-727. Geiselman, R. E., Fisher, R. P., MacKinnon, D. P., & Holland, H. L. (1985). Eyewitness memory enhancement in the police interview: Cognitive retrieval mnemonics versus hypnosis. 70, 401-412. Howes, L. M. (2020). Interpreted investigative interviews under the PEACE interview model: Police interviewers’ perceptions of challenges and suggested solutions. Police Practice and Research, 21(4), 333-350. Kidd, W. R. (1940). Police interrogation. R.V. Basuino. McGurk, B. J., Carr, M. J., & McGurk, D. (1993). Investigative interviewing courses for police officers: An evaluation. Police Research Series Paper 4. Police Research Group, The Home Office. Milne, R., & Bull, R. (1999). Investigative Interviewing: Psychology and practice. Wiley. Moston, S., & Engelberg, T. (1993). Police questioning techniques in tape recorded interviews with criminal suspects. Policing and Society, 3(3), 223-237. O'Neill, M., & Jones, D. (2019). Evidence based police training. In A. Griffiths & R. Milne (Eds.), The psychology of criminal investigation: From theory to practice (pp. 249-267). Taylor and Francis. Peel, R. (1829). Principles of law enforcement. Satin, G. E., & Fisher, R. P. (2019). Investigative utility of the cognitive interview: Describing and finding perpetrators. Law and Human Behavior, 43(5), 491-506. Shepherd, E. (1991). Ethical interviewing. Policing, 7, 42-60. Shepherd, E. (1993). Resistance in interviews: The contribution of police perceptions and behaviour. In P. Mathias (Ed.), Aspects of police interviewing (pp. 5-12). British Psychological Society Shepherd, E. (2007). Investigative interviewing: The Conversation Management approach. Oxford University Press. Shepherd, E., & Griffiths, A. (2013). Investigative interviewing. Second edition. Oxford University Press. Shepherd, E., & Kite, F. (1988). Training to interview. Policing, 4(4), 264-280. Shepherd, E., & Kite, F. (1989). Teach 'em to talk. Policing, 5(1), 33-45. Soukara, S., Bull, R., & Vrij, A. (2002). Police detectives’ aims regarding their interviews with suspects: any change at the turn of the millennium? International Journal of Police Science and Management, 4(2), 100-114. Tudor-Owen, J., Scott, A. J., Henry, P. J., & Bull, R. (2016). An exploratory study of the planning and interviewing practices of police recruits in Western Australia. Forensic Update, 120, 20-25. Vanderhallen, M., & Vervaeke, G. (2014). Between investigator and suspect: The role of the working alliance in investigative interviewing. In R. Bull (Ed.), Investigative Interviewing (pp. 63-90). Springer. Walsh, D., & Bull, R. (2010). What really is effective in interviews with suspects? A study comparing interviewing skills against interviewing outcomes. Legal and Criminological Psychology, 15(2), 305-321. Walsh, D., & Bull, R. (2015). Interviewing suspects: examining the association between skills, questioning, evidence disclosure, and interview outcomes. Psychology, Crime & Law, 21(7), 661-680. Walsh, D., & Milne, R. (2008). Keeping the PEACE? A study of investigative interviewing practices in the public sector. Legal and Criminological Psychology, 13(1), 39-57. Wheatcroft, J. M., Wagstaff, G. F., & Russell, K. (2014). Specialist police interviewer perceptions of the enhanced cognitive interview: Usefulness, confidence and witness reliability. Police Practice and Research, 15(6), 505-518.

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Blog 04 But does it work (January 20, 20
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