The growth of technology has created an expansion in the fields of knowledge which are the subject of ‘expert evidence’ in the Australian courts.
Experts are now regularly called upon to give opinions about advancing technologies including encryption, and digital innovations like Bitcoin.
While witnesses can only generally testify about their personal observations, expert witnesses are permitted to express opinions derived from their field of expertise.
Section 79 of the Evidence Act 1995 (NSW) provides that:
(1) If a person has specialised knowledge based on the person’s training, study or experience, the opinion rule does not apply to evidence of an opinion of that person that is wholly or substantially based on that knowledge.
The case of Clark v Ryan  HCA 42 allows for expert opinions in respect of fields that are “… such that inexperienced persons are unlikely to prove capable of forming a correct judgment upon it without such assistance.”
Bitcoin as an emerging field
Created by underground technology enthusiasts in 2008, Bitcoin is a digital currency which operates between individual users, without control or interference by central banks or the state. Bitcoin-to-Bitcoin transactions are made by digitally exchanging anonymous, heavily encrypted codes across peer-to-peer (P2P) networks.
In 2015, 65% of the US general public was “not at all familiar” with Bitcoin. Of those who were aware, 84% had never used the currency. Of 3,148 Australians surveyed in April 2015, only one in three had any idea of what Bitcoin was. In 2014, about 1000 Australian businesses accepted Bitcoin payments, with the number growing steadily since that time.
Just as the ‘internet’ was difficult to explain when it first came into existence, Bitcoins are proving to be a confusing concept to jurors. This has led legal commentators to conclude that the technology falls squarely within the Clarke v Ryan principle.
Expertise in Bitcoin
A new Federal Court Practice Direction now requires reports to detail the qualifications of a person who professes to be an expert, including their training, study, or experience upon which their ‘specialised knowledge’ is based.
Despite their being no specific qualification for becoming an expert in Bitcoin – as may be the case for DNA or fingerprint analysis – it could be argued that expertise in Bitcoin may be derived from a range of fields including encryption, cryptology, finance, computer science, programming and IT security.
Acceptable fields of expertise
US courts require a field of expertise to be specific and well-established before being capable of forming the basis for an expert opinion.
The rationale for the requirement is that ‘junk science’ should be excluded from court proceedings, as its use can lead to false findings.
The US ‘Daubert’ standard of admissibility takes into account:
- Empirical testing;
- Peer review and publication;
- Known or potential error rate;
- The maintenance of standards and controls concerning its operation; and
- General acceptance by a relevant scientific community.
There is no such ‘field of expertise rule’ in the Australian Evidence Acts. Indeed, the NSW Court of Criminal Appeal specifically excluded the requirement in the case of R v Tang  NSWCCA 167.
An expert does not, therefore, need their field be ‘reliable’ in order for their opinion to be capable of use in an Australian court. They need only to possess some particular specialised knowledge beyond that of a layperson, and their opinion must be based wholly or substantially on that knowledge.
Lack of a ‘reliability’ rule
The US National Research Council Report in 2009 asserts; “In a number of forensic science disciplines, forensic science professionals have yet to establish either the validity of their approach or the accuracy of their conclusions, and the courts have been utterly ineffective in addressing the problem.”
Recent examples of junk science in Australian Courts include facial mapping, voice recording, and hair and bite mark comparison, none of which have been scientifically validated.
In R v Tang, the facial mapping expert admitted that she was not aware of any validation of her methods. She agreed that the appearance of facial features can be altered by photographic angles, motion blur, lighting, and the translation of data format, none of which she had studied in the case. In spite of this, she “was not prepared to admit that she could be mistaken.”
This poses a significant problem because forensic scientists are often seen as an absolute authority for their opinion. Rhona Wheate suggests that the TV popularisation of forensic science has created the impression that forensic evidence is ‘irrefutable and always leads to convictions’.
In Honeysett v R  HCA 29, for example, rather than relying on conflicting eye-witness evidence, the jury relied on body-mapping by anatomist Professor Henneberg. His comparison of the accused to CCTV footage required no formal qualifications though, meaning that his subjective impressions were given undeserved weight.
Defence lawyers may lack the knowledge to acknowledge these weaknesses in emerging fields, making it difficult for juries to make rational evaluations. Researcher Greg Edmond further commented that the accused should not be responsible for exposing fundamental limitations within expert evidence called by the state.
In this regard then, there must be more protections for defendants from this unfair burden of proving the limitations of opposing experts. Standards of admissibility must account for reliability, or else the Court will continue to allow junk science to influence jurors, increasing the risk of wrongful convictions.