Unsound Law: Issues with ('Expert') Voice Comparison Evidence

Article excerpt

[Since the 1980s the volume of identification evidence derived from surveillance devices and telephones has increased dramatically. This article offers a critical analysis of the forensic use of voice comparison and identification evidence. First, it reviews the contemporary jurisprudence in common law and uniform Evidence Act jurisdictions, then explains some of the limitations with our current responses to voice evidence, particularly the dramatic rise in the reliance placed upon the opinions of investigators, interpreters and (other ad hoc) 'experts' as well as the willingness to leave voice comparison evidence (and exercises) to juries. Employing an original multi-disciplinary methodology, the article then problematises legal practice through the introduction of relevant social science research on voice comparison (and recognition). As the authors explain, relevant scientific research and opinions are rarely adduced by lawyers or referred to by trial judges when instructing or cautioning juries. In consequence, it is suggested that current legal rules and procedures do not adequately represent what is known beyond the courts and thereby fail to embody fundamental criminal justice principles concerned with truth and fairness.]


I    Introduction
II   Overview of the Australian Law on Voice Comparison Evidence
III  Voice Comparison Cases: An Introductory Sample
IV   Cross-Racial and Cross-Lingual Comparisons by Displaced Listeners
V    Cross-Lingual Jury Comparisons
VI   Scientific Research: Human Voice 'Identification' beyond the
       A Introduction and Some Conceptual Clarification
       B Familiarity
       C Factors Affecting Voice Comparison and Recognition
VII  Reconsidering Riscuta and Korgbara
VIII Deaf and Dumb Justice: Scientific Research and Legal Practice
       A Remedial Psychologists?
       B Judicial Directions and Other 'Solutions'.
       C Scientific Voice Comparison and Probabilistic Evidence
       D Voice Identification Parades for Those Who Become Familiar
         after the Fact
       E Discussion
IX   Silence in Court?


In recent years most Australian courts have become remarkably receptive to comparison evidence derived from audio surveillance technologies. In most cases the courts are considering whether to allow witnesses to give evidence of their opinion as to whether a voice captured on a surveillance tape is the same as the voice of the accused. These witnesses are often, though not always, characterised as 'experts', (1) sometimes by virtue of formal training, but mostly by virtue of 'displaced' exposure--ie remote listening, usually repeatedly--to the tapes in question. Often characterised as 'identification' evidence, displaced comparison evidence is situated awkwardly at common law and does not come within the definition of 'identification evidence' under the uniform Evidence Acts ('UEAs'). (2) Australian courts have become reluctant to impose specific conditions on the admission of voice comparison evidence. Indeed, they have demonstrated a willingness to allow juries to make their own assessments of direct and displaced witness testimony and, where tape recordings (or voices) are available, to undertake their own voice comparisons.

This article aims to examine recent trends in voice comparison and identification evidence, focusing primarily upon the evidence of 'displaced non-familiars' and the use of voice recordings. (3) It is our contention that decisions on the admissibility of voice comparison evidence display a troubling readiness to admit incriminating opinion evidence of unknown probative value, an overreliance on the capacity of traditional features of the adversarial trial--such as cross-examination and warnings to juries--to expose and convey weaknesses, and a hostility towards attempts to require some assessment of the methods used by displaced non-familiars to provide opinions about identity. …