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This page is designed to give busy people a step-by-step introduction to the serious problems with the use of indistinct covert recordings as evidence in criminal trials.

For further detail, please explore the website you are currently on, follow any of the numerous references in the articles below – or don’t hesitate to contact me directly.

1. The most efficient starting point is this 23-minute video

1.a) Presentation at National Judicial College, Australia, March 2017

This has the advantage of brevity while also allowing you to hear the audio examples – and most importantly the audience’s reaction to the audio. If you like it, you could follow up with the Valentine’s Day talk to the Australian Academy of Forensic Sciences – complementary issues, from a more scientific perspective, compared to the legal aspects in the NJCA talk. Or try one of the other talks at

2. Then try one or more of these short written introductions

2.a) Burridge, K. (2017). The dark side of mondegreens: how a simple mishearing can lead to wrongful conviction. The Conversation

By the brilliant, renowned and always entertaining Professor Kate Burridge.


2.b) Fraser, H. (2017). Real forensic experts should pay more attention to the dangers posed by “ad hoc experts” (Guest Editorial). Australian Journal of Forensic Sciences.



2.c) Fraser, H. (2017). How interpretation of indistinct covert recordings can lead to wrongful conviction: A case study and recommendations for reform. In R. Levy, et al. (Eds.), New directions for law in Australia: Essays in contemporary law reform (pp. 191–200). Canberra: ANU Press.

A written version of Item 1.a) above, with more detailed background.


2.d) Fraser, H. 2013. Covert recordings as evidence in court: the return of police “verballing?” The Conversation

Around the same time as mandatory recording of police interviews put at end to ‘fabricated confessions’ , other reforms were inadvertently giving police a new way to “put words in suspects’ mouths” – this time without even needing a conscious intention to do so.

3. Follow on with this recent experiment – extraordinary, easy to read and compelling

3.a) Fraser, H. (2017). “Assisting” listeners to hear words that aren’t there: Dangers in using police transcripts of indistinct covert recordings. Australian Journal of Forensic Sciences.

Results are reported of a new experiment using an indistinct covert recording from a real murder trial, along with the police transcript admitted to ‘assist’ the court to hear its contents. Previous research using the same material has shown that the police transcript is inaccurate, yet nevertheless highly influential on the perception of listeners ‘primed’ by seeing words it suggests. The current experiment examines the effects of priming participants with a made-up phrase that vaguely fits the acoustics of one section of the recording. Results indicate that a very high proportion of listeners are easily ‘assisted’ to ‘hear’ the made-up phrase. Discussion argues that audio of this quality should only be used as evidence if accompanied by a reliable independent transcript.

4. One or more of these extended treatments will round out the background

From a legal perspective

4.a) Fraser, H. (2015). Transcription of indistinct covert recordings used as evidence in criminal trials. In H. Selby & I. Freckelton (Eds.), Expert Evidence. Thomson Reuters.

Goes over the development of the ‘aide memoire’ and ‘ad hoc expert’ concepts, and explains how they misunderstand the nature of speech perception.

4.b) Fraser, H. (in press). Thirty years is long enough: It’s time to create a process that ensures covert recordings used as evidence in court are interpreted reliably. Journal of Judicial Administration. (Pre-publication – ask for copy)

This paper outlines a number of serious problems arising from the handling within the legal process of covert recordings used as evidence in criminal trials. These problems relate specifically to four key areas, namely: translation of foreign language material, transcription of indistinct English, attribution of utterances to speakers, and ‘enhancing’ of poor quality audio. The paper traces the problems back to the landmark High Court judgment of Butera 1987, and attributes them to insufficient understanding within the judiciary of well-established but counter-intuitive findings of linguistic science regarding factors that affect the reliable interpretation of recorded speech. Several possible solutions to the problems are canvassed, and it is recommended that the most promising way forward is via enhanced communication and collaboration between law, law enforcement and linguistic science.

From a linguistics perspective

4.c) Fraser, H. (2014). Transcription of indistinct forensic recordings: Problems and solutions from the perspective of phonetic science. Language and Law/Linguagem E Direito, 1(2), 5–21.

Covert recordings (speech captured on audio or video without the knowledge of the speakers) can provide powerful forensic evidence. Unfortunately, however, since it is difficult to control their recording conditions, covert recordings are often indistinct, to the extent the speech is unintelligible to listeners who do not already have knowledge or expectations about their content. This raises the question of how to present the speech evidence in court so that the trier of fact (jury, magistrate, judge, etc.) can make use of the information contained in the recording. In many jurisdictions, the answer is to have a transcript made by those who know the context (typically police working on the case), and provided to the trier of fact as an aid to perception of the speech. The present article outlines several problems with this approach, then suggests some solutions that allow maximal value of the intelligence contained in covert recordings, while reducing the risk of injustice through biased perception of indistinct audio. A key part of the suggested solution is to make a clear distinction between investigative and evidentiary uses of indistinct covert recordings, and to ensure that transcripts of evidentiary recordings be produced by professional transcribers independent of the case.

4.d) Advanced Fraser, H. (in press) Forensic transcription: How confident false beliefs about language and speech threaten the right to a fair trial in Australia. Australian Journal of Linguistics. (Pre-publication – ask for a copy)

Everyday knowledge about language and speech, or ‘folk linguistics’, incorporates a number of false beliefs that have a negative effect in a range of areas, nowhere more so than in the criminal justice system (e.g. Solan, Ainsworth, & Shuy, 2015). One lesser known area where false beliefs have a major impact is forensic transcription (interpretation of indistinct covert recordings used as evidence in criminal trials). Without consultation of the linguistic sciences, the law has developed processes that allow police transcripts to ‘assist’ the courts in making out unintelligible covert recordings (see Fraser, 2017c). The present article uses a case study of a real murder trial to bring the actual and potential injustice this creates to the attention of linguistic science, and examine the issues from a linguistics perspective. Having laid out the problem, it goes on to consider potential solutions, arguing that creating a better process requires deep collaboration between linguistics, law and law enforcement. From linguists, it requires improved theoretical understanding of the nature and structure of the false beliefs that underlie the existing legal processes, as well as development of a more general theoretical account of the process of transcription and the nature of transcripts.

5. Start considering a solution

When you have gained an impression of the dimensions of the problem, it is time to turn to considering the solution. The most important thing is to ensure any solution implemented is a real solution, and not one that in reacting to perception of one set of problems, creates another another set. That means taking time to fully understand the nature and causes of the problems before moving to implement a solution.

If you have been through the background materials and would like to be involved in implementing the solution, please make contact.

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