New article in Griffith Journal of Law and Human Dignity

Enhancing forensic audio: What works, what doesn’t, and why

by Helen Fraser

‘Enhancing’ has become a routine part of preparing indistinct covert recordings for admission as evidence in criminal trials. Typically, evaluation of its effectiveness is seen as a simple matter of listening to determine whether the enhancement sounds ‘clearer’ than the original. This seems like a straightforward approach, but it brushes over many important issues which can adversely affect the fairness of the trial. This article outlines findings from experiments, case studies and scientific literature to show how enhancing can affect perception in surprising and unpredictable ways, without listeners’ conscious awareness. Discussion demonstrates that enhancing exacerbates, rather than mitigates, known risks of the jury being misled by an unreliable transcript. The conclusion indicates the direction in which to seek better procedures.





A Enhancing is Not a Science But an Art

B Enhancing Does Not ‘Reveal’ Words ‘Masked’ by Noise

C Enhancing Can Make Indistinct Audio Sound More Clearly Like Something it is Not

D Enhancing Exacerbates, Rather Than Mitigates, the Risk of Listeners Being Misled by an Unreliable Transcript

E Even Neutral, Responsible Listeners Cannot Reliably Evaluate the Effect of Enhancing by Observing Whether it Makes Words ‘Sound Clearer’

F What ‘Enhancing’ Can and Cannot Do




The right to a fair trial is a cornerstone of a functioning democracy. Realistically, we must accept that it is not possible, in practice, to guarantee that every trial will be perfectly fair: there are simply too many contingencies that can influence any particular outcome. However, it is important to maintain confidence that, in principle, legal procedures, followed diligently, do promote fairness.
The present paper canvasses a threat to fairness that, rather than arising from contingencies, is baked into established legal procedures — specifically, procedures for the handling of indistinct covert recordings used as evidence in criminal trials. As they currently stand, even if followed perfectly, these procedures cannot guarantee a fair outcome.

Reference and link

Fraser, H. (2020). Enhancing forensic audio: What works, what doesn’t, and why. Griffith Journal of Law and Human Dignity, 8(1), 85–102.

Other articles in the same issue

  • Response to White and Willmott by Rodney Syme
  • When Transparency Can Be Deadly: Reporting of Identifiable and Locatable Personal Information in AAT Couple Rule Decisions that Involve Domestic Violence by Lyndal Naomi Sleep, Luisa Gras Diaz
  • Queering Asian Values by Erich Hou
  • Dignity and Culture in Dispute Resolution by Lola Akin Ojelabi
  • The Quest for Justice in a Time of Global Uncertainty by Fiona McLeod
Sign up here for occasional news about Forensic Transcription (no spam!)