‘A new and more rigorous approach’ to expert evidence in England and Wales?

AuthorTony Ward
Date01 October 2015
Published date01 October 2015
Subject MatterArticles
‘A new and more rigorous
approach’ to expert evidence
in England and Wales?
Tony Ward
University of Hull, UK
An amendment to the Criminal Practice Direction issued by the Lord Chief Justice of England
and Wales lays down guidance for judges to follow in determining whether expert evidence is
‘sufficiently reliable to be admitted’. Although the guidelines are based on those proposed by
the Law Commission in 2011, they do not include a definition of ‘sufficiently reliable’, such as
would have been provided by the Law Commission’s Draft Bill, which the government declined
to introduce. A criterion of ‘sufficient reliability’ must therefore be found within the common
law. This article argues that ‘sufficient reliability’ is an aspect of ‘helpfulness’ and reflects the
principle that experts should provide the jury with criteria with which to assess the weight of
their evidence. Reliable evidence, in short, is evidence that provides the jury with sound
reasons for relying on it. This criterion could be as rigorous as that proposed by the Law
Commission, and possibly more so.
Criminal Procedure Rules, expert evidence, reliability, relevance
With effect from 6 October 2014, a new Part 33A of the Criminal Practice Direction sets out guidelines
for judges to follow when determining the admissibility of expert evidence in England and Wales.
guidelines are based on those proposed by the Law Commission in its report of 2011 (Law Commission,
2011). As Lord Thomas CJ, the author of the additions to the Practice Direction, has acknowledged, this
Corresponding author:
Tony Ward, University of Hull, Law School, Cottingham Road, Hull HU6 7RX, UK.
E-mail: a.ward@hull.ac.uk
1. Practice Direction (Criminal Proceedings) [2013] EWCA Crim 1631; [2013] 1 WLR 1634, as amended by Practice Direction
(Criminal Proceedings: Various Changes) [2014] EWCA Crim 1569; [2014] 1 WLR 3001, (cited hereafter as ‘CPD’).
The International Journalof
Evidence & Proof
2015, Vol. 19(4) 228–245
ªThe Author(s) 2015
Reprints and permissions:
DOI: 10.1177/1365712715591471
exercise of the inherent power of the courts to regulate their own proceedings
amounts to ‘a novel way
of implementing an excellent report’ (Thomas, 2014) after the government declined to legislate as the
Commission had recommended.
The government’s decision not to legislate was based partly on concerns about the cost of some of the
Law Commission’s proposals and partly on the view that much of what the Law Commission wanted
could be achieved without primary legislation (Ministry of Justice, 2013). To this end the government
specifically asked the Criminal Procedure Rules Committee to draft rules implementing the Commis-
sion’s proposal for courts to be provided with more information to assess the reliability of expert evi-
dence (Ministry of Justice, 2013: paras. 4, 12). The Law Commission intended the required
information to assist the courts in applying a new statutory test: whether expert evidence was ‘suffi-
ciently reliable to be admitted’ (Law Commission, 2011: para. 7.21). The Practice Direction cites Rv
Dlugosz, one of several recent cases where the Court of Appeal stated that expert evidence must be ‘suf-
ficiently reliable to be admitted’ as a matter of common law.
The Practice Direction encourages judges
to consider the same factors that would have been relevant to the statutory test when applying the com-
mon law test. In this way, the CPD at least partly encapsulates the Law Commission’s central recom-
mendation, while other proposals deemed unduly costly—meetings of experts chaired by the judge,
and court-appointed experts to advise on reliability (Law Commission, 2011: Part 6 and paras. 7.46–
7.52)—are left on the shelf. Leveson LJ has predicted that it will simplify proceedings, because the ‘new
and more rigorous approach on the part of advocates and the court’ that it requires ‘should avoid mis-
understandings about what is (and what is not) appropriately included in an expert’s report and so either
avoid, or at least render far more straightforward, submissions on admissibility’.
To make submissions on admissibility straightforward surely requires that the threshold of admissi-
bility be clearly defined. By itself, however, the Practice Direction cannot fill the gap left by the non-
implementation of arguably the Law Commission’s most important recommendation: its proposed
statutory definition of what would constitute ‘sufficient’ reliability.
As Dale Nance has pointed out
in the context of the US Daubert decision, the concept of ‘sufficient reliability’ is vacuous in the absence
of some reasonably determinate criterion of what degree of reliability is ‘sufficient’: it is not enough to
specify (as the Practice Direction does) the factors that will weigh for and against admissibility, without
any indication of the weight required for admission or exclusion.
The Law Commission’s test, as
discussed below, was drafted somewhat ambiguously, but when taken together with the Commission’s
examples of how it might be applied, it was reasonably clear. In the absence of legislation, a criterion of
‘sufficient reliability’ has to be extrapolated from the common law authorities. The Practice Direction
does not tell us how to do this, nor is any clear criterion of admissibility to be found in the case law.
In a previous article I suggested one way in which something close to the Law Commission’s test
could be implemented without legislation (Ward, 2013). Any prosecution evidence that would fail the
Law Commission’s test could, I argued, be excluded on the ground that its prejudicial effect exceeded its
probative value. In essence, the Law Commission’s test would exclude evidence that either had no sound
basis at all, or was more strongly expressed than was warranted by whatever sound basis it had. The
problem with many kinds of forensic science evidence was likely to be not that it completely lacked
a sound basis but that a particular opinion was too strongly expressed. Such an opinion would have a
potentially prejudicial effect—inviting the jury to give undue weight to the evidence—and it could have
no probative value beyond what a more cautiously expressed opinion would have. Therefore it should be
2. The nature of Practice Directions is examined in Bovale Ltd. vSecretary of State for Communities and Local Government
[2009] EWCA Civ 171; [2009] 3 All ER 340.
3. [2013] 1 Cr App R 425, [11], cited in CPD 33A. 4.
4. RvH[2014] EWCA Crim 1555, [44].
5. Draft Criminal Evidence (Experts) Bill—in Law Commission, 2011: Appendix A, Clause 4(1).
6. Nance, 2003: 197; Daubert vMerrell Dow Pharmaceuticals 509 US 579 (1993).
Ward 229

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