1.1 This submission is in response to the proposed reform model concerning the giving of
concurrent evidence, (also known by the sobriquet, “hot-tubbing”) in New South
Wales criminal jury trials, in which experts give their evidence concurrently. This
method is common in Australian civil trials and has been increasingly used in
certain jurisdictions. The purpose of this proposed model is to identify issues
involving biased (single) expert evidence and the reliability of scientific evidence,
particularly in criminal litigation. This submission explores whether concurrent
evidence is the preferred model and whether this method should be utilised in New
South Wales criminal trials.

1.2 This submission will respond to the following questions:
i. The current law and procedure concerning the presentation of expert evidence
under s 79 of the Evidence Act 1995 (NSW) in criminal trials in New South Wales.
ii. Theory and policy underlying the current criminal trial procedure.
iii. The introduction of the proposed amendment in criminal jury trials.
1.3 Overall, the submission highlights the advantages and disadvantages of concurrent
evidence by which expert witness evidence is given in court. Finally, it argues that
concurrent evidence would seem to offer considerable benefit for the improvement of
adversarial legal processes (practice), however, it should not be considered in criminal

2.1 The function of an expert witness is to provide the court with specialised knowledge1
and expertise so that the fact-finder can resolve the dispute between the litigants. The
Australian Law Reform Commission (ALRC) clarified the meaning of an expert:
An expert should be defined as a person who ‘has special knowledge, skill, experience
or training about a matter’, and that he generally be able to give opinion evidence that
utilises his specialised knowledge, skill, experience or training .M Experience can be a
sounder basis for opinion than study. Not to include special experience as a
qualification would keep valuable evidence from the courts.
2.2 It should be noted that specialized knowledge may have been gained from different
types of training, study and experience.
2.3 In Quick v Stoland,
3 a case involving the expert evidence of a qualified accountant,
Finkelstein J stated that “[t]he function of the expert is to provide the trier of fact, judge
or jury, with an inference which the judge or jury, due to the technical nature of the facts,
is unable to formulate”.
2.4 The word opinion is not defined in the Evidence Act 1995 (NSW) (will herein be
referred to as “Evidence Act”), however it is generally understood as “an inference
drawn from facts”4 or “a conclusion, usually judgmental or debatable, reasoned from
Section 79 of the Evidence Act governs the admission of expert opinion
evidence. As pointed out by Spigelman CJ (with Simpson and Adams JJ agreeing)
explained the operation of s 79:
Section 79 has two limbs. Under the first limb, it is necessary to identify ‘specialised
knowledge’, derived from one of the three matters identified, ie, ‘training, study or
experience’. Under the second limb, it is necessary that the opinion be ‘wholly or substantially based on that knowledge’. Accordingly, it is a requirement of admissibility
that the opinion be demonstrated to be based on the specialised knowledge.

2.5 The meaning of the phrase “specialised knowledge’ for the purposes of s 79 of the
Evidence Act has been held by Spigelman CJ in Tang; where Spigelman CJ stated
that ‘the focus must be on the words ‘specialised knowledge’ and not on the
introduction of an extraneous idea such as ‘reliability”’.7

2.6 At common law, when considering the admissibility8 of expert opinion, the opinion
from the expert witness must derive from a “field of expertise”. Odgers notes9
“[t]here are also authorities which adopt a test of ‘general acceptance”’ for the
evidence to be admissible “in the relevant scientific discipline,10 authorities which
require a court to make an assessment of ‘reliability’11 and authorities which adopt
both tests’’.12

2.7 The burden is on the party seeking to get the evidence in to test its reliability. Opinion
evidence is admissible if it is wholly or substantially based upon specialised knowledge
on the person’s training, study or experience.13
Once expert opinion evidence adduced
by the state under s 55 of the Evidence Act, the Act confers a discretion upon judges in
ss 135–137 — where a judge may exclude evidence otherwise admissible evidence
“going before a criminal trial through recourse to the exclusionary discretions”.14
would occur in such circumstances “where the probative value of the evidence was
outweighed by the danger of unfair prejudice to the accused”.

3.1 The Evidence Act applies in New South Wales courts. Under the common law, expert
witnesses in adversarial criminal and civil proceedings have a privileged position and
are permitted to give expert “opinion in much broader circumstances than lay
In practice, experts’ overriding duty is to the court, and not to the party
by whom they are paid. However, this is not always the case, particularly where
Lawyers look for an expert who will advance their client’s case.
3.2 Most experts are familiar with adversarial (or common law) system and know what is
expected when they give evidence before a criminal court. How an expert’s evidence
is presented depends upon the rules of the court. When experts give evidence from
the witness box, the defendant’s advocate or prosecutor will lead through their
evidence-in-chief both to develop their side’s case, and then cross-examined,
sometimes at length by the other side.
3.3 Lord Justice Leveson considers problems with the current approach, particularly in
England and Wales, and notes that “there exists a real difficulty that just because an
expert’s evidence is presented as ‘scientific’, it may be taken to be reliable”.17
proposition also raises concern with Professor Edmond and Roberts where they argue
that the “admissibility and use of incriminating expert opinion evidence at trial — ‘[t]he
law regulating the reception of this form of evidence is the subject of ongoing concern
and controversy”’.18

3.4 Edmond further argues that experts report “leaves the reader in little doubt that
expert partisanship is the most significant problem”.19
Empirical study supports this
judicial attitude20. Even though the vast majority of surveyed judges considered
expert evidence is useful for fact-finding. However, judicial officers still express
concerns about the prevalence of “bias, the use of language that is difficult to

understand, failure to stay within parameters of expertise; non-responsiveness to
questions; failure to prove the bases of opinions; cross-examination not making the
expert accountable and the complexity of evidence”21

3.5 Edmond expressed concerns, particularly when judges in “accusatorial jurisdictions”,
to some extent, appear to be “overly receptive to expert opinion evidence adduced”
and seem to be largely oblivious to problems with opinion evidence produced by the
institutionalised forensic sciences: Wood v The Queen22
. In this particular case, there
has been a robust challenge to the reliability of the expert sciences and medical
evidence adduced by the Crown.23

4.1 The procedure of concurrent evidence (“hot-tubbing”) model is a departure from the
traditional adversarial method. In civil proceedings, concurrent evidence involves
multiple experts to be sworn in together and present their expert evidence to the court
concurrently. Chief Justice McClellan explained this process thus:
Concurrent evidence is essentially a discussion chaired by the judge in which the
various experts, the parties, the advocates and the judge engage in a cooperative
endeavour to identify the issues and arrive where possible at a common resolution of
them. Where resolution of issues is not possible, a structured discussion, with the judge
as chairperson, allows the experts to give their opinions without the constraints of the
adversarial process and in a forum which enables them to respond directly to each
other. The judge is not confined to the opinion of one advisor but has the benefit of
multiple advisors who are rigorously examined in public.24
4.2 The advantages of concurrent evidence in litigation enable experts to prepare and
exchange their written reports. This allows experts to meet before the trial and identify
the areas on which they have a common view and areas where they disagree. No
doubt, this process enhances efficiency by reducing cost and the time taken to resolve
matters before the commencement of a trial. One of the important features of this model

is it has the potential to reduce the level of partisanship of experts (the notion of ‘guns
for hire’) and narrowing the contentious issues and arrive, at a common resolution.
What follows is a discussion, which is managed by the judge, with the assistance of
advocates and in the presence of the witnesses.25

4.3 On the other hand, this process has its disadvantages, viz, criminal context. Concurrent
process in criminal trials with juries would do nothing to solve or refine complex issues;
the hot tub method is designed for simpler matters.
4.4 The process allows judges to have a far greater active role and “tends to encourage
judicial intervention”.26
However, this raises issues in terms of rectitude, proportionality
and procedural fairness. It is fair to say that this process disrupts the adversarial trial.
The traditional adversarial procedure is that a judge is supposed to be impartial and let
counsel run their case. Thus, the concern is that if judges get too involved, then the
questions of impartiality arises: are they actually stepping down from the bench and
taking on a different role? The other concern is that lawyers are temporarily
marginalised and may lose control of how they present their evidence in court
proceedings as a whole.
4.5 As noted by Rares J noted, “[n]ot all cases will suit the process. It may be that in patent
cases, where the whole case revolves around conflicts within fields of expertise,
concurrent evidence is not likely to assist a judge”.27
An unfavourable inference may
be drawn from this observation where convoluted cases are unlikely to benefit from
concurrent evidence, particularly in complex criminal trials.
4.6 The other alternative is a court-appointed experts — acting as neutral experts can
provide to the court professional opinion “not directly contaminated by the partisanship
of the parties appearing in litigation”.28
However, this may increase considerable
pressure on the legal system

5.1 The submission has identified some of the issues involved in providing concurrent
evidence. Whilst the concurrent evidence procedure in civil jurisdiction has some
advantages (depending upon particular case) over the traditional form of adducing
evidence. Especially in situation where there are more than two experts, enabling
issues to be crystallised. The process can be efficient and effective, and arguably be
of benefit to all parties involved. The method can save court time “while reducing the
overall length and cost of the proceedings”.29

5.2 Edmond concludes his study by stating: ‘Concurrent evidence is not a panacea for
partisanship, adversarial bias, or the difficulties created by expert disagreement and
decision making in the face of uncertainty. Even when experts and lawyers cooperate
and the procedures reduce the length of the proceedings, concurrent evidence can
leave the fact finder with a messy transcript and conflicting reports, and it can require
more pre-trial activity and impose higher costs on the parties.’30
Therefore, not all cases
will suit the concurrent evidence method, as explained by Rares J.
5.3 Whatever the rational for introducing of concurrent expert evidence in criminal jury trials
in New South Wales, if the proposed model goes ahead, there will be significant change
for lawyers, judges, juries and experts involved.

A Articles/Books/Reports
Australian Law Reform Commission, Evidence, Report No 26 Interim (1985) vol 1, 742
Chief Justice Peter McClellan, ‘New Method with Experts Concurrent Evidence’ (2010) 3(1)
Journal of Court Innovation 259
Edmond, Gary, ‘Judging Surveys: Experts, Empirical Evidence and Law Reform’ (2005) 33(1)
Federal Law Review 95
Edmond, Gary, ‘Merton and the Hot Tub: Scientific Conventions and Expert Evidence in
Australian Civil Procedure’ (2009) 72 Law and Contemporary Problems 159
Edmond, Gary, and Mehera San Roque, ‘The Cool Crucible: Forensic Science and The Frailty
of the Criminal Trial’ (2012) 24(1) Current Issues in Criminal Justice 51
Edmond, Gary, and Andrew Roberts, ‘Procedural Fairness, the Criminal Trial and Forensic
Science and Medicine’ (2011) 33(3) Sydney Law Review 359
Edmond, Gary, ‘Specialised Knowledge, The Exclusionary Discretions And Reliability:
Reassessing Incriminating Expert Opinion Evidence’ (2008) 31(1) University of New South
Wales Law Journal 1
Freckelton, Ian, and Hugh Selby, Expert Evidence: Law, Practice, Procedure and Advocacy
(Lawbook, 4th ed, 2009)
Justice Steven Rares, “Using the ‘hot tub’: How Concurrent Expert Evidence Aids
Understanding Issues” (2010-2011) Journal of the NSW Bar Association 64
Lord Justice Brian Leveson, ‘The Expert Debate: Setting The Limits On The Use Of Expert
Evidence’ (2011) 10(2) The Judicial Review 119
Odgers, Stephen, Uniform Evidence Law (Lawbook, 9th ed, 2010)
B Cases
Allstate Life Insurance Co v ANZ Banking Group Ltd (No 5) (1996) 64 FCR 73
Casley-Smith v Evans & Sons Pty Ltd (No 1) (1988) 49 SASR 314 FC
Harrington-Smith v Western Australia (No 2) (2003) 130 FCR 424
Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705
Quick v Stoland (1988) 157 ALR 615
R v Carroll (1985) 19 A Crim R 410 R v Gilmore [1977] 2 NSWLR 935
R v Lewis (1987) 29 A Crim R 267
R v Tang (2006) 65 NSWLR 681
RW Miller & Co Pty Ltd v Krupp (Australia) Pty Ltd (1991) 34 NSWLR 129
Sydneywide Distributors Pty Ltd v Red Bull Australia Pty Ltd [2002] FCAFC 157
Wood v The Queen [2001] NSWCCA 228
C Legislation
Evidence Act 1995 (NSW)

John Makou
Senior Associate | Lawyer