This article examines the standards governing the admission of new types of expert evidence. Based on the rules of evidence and procedure in Australia, it explains how judges have been largely uninterested in the reliability of expert opinion evidence. Focused on the use of CCTV images and covert sound recordings for the purposes of identification, but relevant to other forensic sciences, the article explains the need for interest in the reliability of incriminating expert opinion evidence. It also explains why many of the traditional trial safeguards may not be particularly useful for identifying or explaining problems and complexities with scientific and technical evidence. In closing, the article argues that those developing new types of evidence and new techniques, whether identification-based or derived from IT, camera or computer forensics, need to be able to explain why it is that the court can have confidence in any opinions expressed.
2. The Australian Admissibility Framework
How have new forms of expert identification evidence been received in Australian courtrooms? To understand recent developments we need to review the rules of admissibility prescribed by the Uniform Evidence Law (UEL) and the common law.1 Here, it is useful to explain that there are basically two systems governing the admissibility of expert opinion evidence in Australia. The most recent, the UEL, is a statutory regime based on a series of substantially similar evidence acts applicable in New South Wales (NSW), Tasmania, the Australian Capital Territory, and the Federal Court. Significantly, it will soon operate in Victoria. The alternative system is the common law (and several parochial acts), applicable in Queensland, Western Australia, South Australia, the Northern Territory and Victoria (in the interim).
According to the UEL, to be admissible all evidence must be relevant:
Evidence is relevant if it has probative value. The UEL Dictionary explains that the “probative value of evidence means the extent to which the evidence could rationally affect the assessment of the probability of the existence of a fact in issue.” Consequently,
55 Relevant evidence
The evidence that is relevant in a proceeding is evidence that, if it were accepted, could rationally affect (directly or indirectly) the assessment of the probability of the existence of a fact in issue in the proceeding. …
Normally, even if relevant, opinions are presumptively inadmissible. Under the UEL the opinion rule (section 76) states that “evidence of an opinion” is not admissible “to prove the existence of a fact about the existence of which the opinion was expressed”. This means that witnesses cannot usually express their opinions about issues relevant to facts in dispute during proceedings. There are, however, several exceptions to the exclusionary impact of the opinion rule.2 Although it does not attempt to codify the common law, section 79(1) provides the major exception for expert opinion evidence. It reads: