Law Commission Consultation: The Proposals
The Law Commission Consultation, on introducing a pre-trial
assessment of expert evidence, contains two formal proposals
and offers thoughts on three allied issues
The following summarises these proposals. The UK Register of Expert Witnesses has prepared some analysis of these proposals which is available at http://www.jspubs.com/Surveys/LC0904/index.cfm
Proposal 1: A gate-keeper role
The Law Commission’s key proposal is that there should be an explicit "gate-keeping" role for the trial judge with a clearly defined test for determining whether proffered expert evidence is sufficiently reliable to be admitted. The application of this test would determine whether the tendered evidence is admissible as a matter of law.
After first determining that the proposed expert evidence is logically relevant to the disputed matter, that it would provide the jury with substantial assistance and that the witness is truly expert and able to provide an impartial opinion, the judge would need to address the gate-keeping question. The question is whether the evidence is sufficiently reliable to be considered, and ultimately accepted, by a Crown Court jury.
The Law Commission provisionally proposes that there should be a statutory provision along the following lines:
(1) The opinion evidence of an expert witness is admissible only if the court is satisfied that it is sufficiently reliable to be admitted.
(2) The opinion evidence of an expert witness is sufficiently reliable to be admitted if:–
(a) the evidence is predicated on sound principles, techniques and assumptions;
(b) those principles, techniques and assumptions have been properly applied to the facts of the case; and
(c) the evidence is supported by those principles, techniques and assumptions as applied to the facts of the case.
(3) It is for the party wishing to rely on the opinion evidence of an expert witness to show that it is sufficiently reliable to be admitted.
Thus, the trial judge would not only consider the reliability of the expert’s hypothesis, methodology and assumptions, but would also examine how the expert has applied them to the case and, if properly applied, whether the expert’s conclusion is logically sustainable.
Such a test would put experts on notice that they will be expected to provide the trial judge with evidence about the basis of their expert opinion sufficient to enable the judge to conclude that their evidence would provide the jury with reliable information.
Acknowledge the distinction between scientific and experiential expertise
Whilst much expert evidence is based in science, there is the whole area of expert evidence based on experience (e.g. forensic accountancy or experts in custom and practice for a particular trade). The Law Commission recognises this and proposes two distinct sets of guidelines to cover each type of expert evidence.
For scientific expert evidence it proposes the following:
In determining whether scientific (or purportedly scientific) expert evidence is sufficiently reliable to be admitted, the court shall consider the following factors and any other factors considered to be relevant:
- whether the principles, techniques and assumptions relied on have been properly tested, and, if so, the extent to which the results of those tests demonstrate that they are sound;
- the margin of error associated with the application of, and conclusions drawn from, the principles, techniques and assumptions;
- whether there is a body of specialised literature relating to the field;
- the extent to which the principles, techniques and assumptions have been considered by other scientists – for example in peer-reviewed publications – and, if so, the extent to which they are regarded as sound in the scientific community;
- the expert witness’s relevant qualifications, experience and publications and his or her standing in the scientific community;
- the scientific validity of opposing views (if any) and the relevant qualifications and experience and professional standing in the scientific community of the scientists who hold those views; and
- whether there is evidence to suggest that the expert witness has failed to act in accordance with his or her overriding duty of impartiality.
It would be for the trial judge to determine whether a field of expertise is to be classified as scientific and assessed in accordance with these guidelines. With regard to factor (a), the expert would need to show that the experimental or observational tests were conducted in an objective, scientifically valid way with appropriate comparators (for example, control groups) and safeguards (for example, measures to protect against contamination).
For experiential expert evidence it proposes the following guidance:
In determining whether experience-based expert evidence is sufficiently reliable to be admitted, the court shall consider the following factors (where applicable) and any other factors considered to be relevant:
- the expert’s qualifications, practical experience, training and publications and his or her standing in the professional or other expert community;the extent to which the basis and validity of the expert’s opinion can be explained, with particular reference to:
- the extent to which the basis of the opinion (for example, any assumption relied upon) has been verified or discredited;the specific instances which support the claim to experience-based expertise;the bearing those instances have on the matter(s) in issue; and
- whether the expert’s methodology or reasoning has previously resulted in a demonstrably valid or erroneous opinion;
- whether there is a body of specialised literature relating to the field of expertise and, if so:
- the extent to which it supports or undermines the expert’s methodology and reasoning; and
- the extent to which the expert’s methodology and reasoning are recognised as acceptable amongst his or her peers;
- whether there is evidence to suggest that the expert has failed to act in accordance with his or her overriding duty of impartiality.
Based on this guidance, the reliability of expert testimony on forensic document examination would be determined on the basis of, amongst other things, the witness’s experience, the number of standard points of comparison used and a detailed description of the process by which the expert reached the given opinion.
In the areas of professional, non-scientific expertise where there are well-accepted practices and methodologies, e.g. accountancy, it should be sufficient that the expert followed accepted practices and has provided a sufficient explanation of what was done.
Proposal 2: The onus of persuasion
The Law Commission proposes that any party to an action, or the judge, should be able to raise the question of evidential reliability as a preliminary issue. If raised:
- the judge could take "judicial notice" of the evidentiary reliability of the proposed evidence if reliability has already been clearly established (and no new developments have arisen), or if the expert evidence is patently unreliable (e.g. a party wished to adduce expert evidence from an astrologer) the judge could hold that it is inadmissible without the need for detailed investigation, or
- the judge would investigate the evidentiary reliability of the proffered expert evidence in accordance with the three-stage test. The party tendering the evidence would need to demonstrate that the expert’s hypothesis and methodology comprise a reliable basis for the expert testimony. In accordance with the Criminal Procedure Rules, the expert would have a duty to provide details of research findings which undermine the validity of his hypothesis or reasoning.
Importantly, at no stage of this inquiry into the reliability of the underpinning body of knowledge is it incumbent on the judge, the parties or the experts to show or determine if the opinion given by the expert is actually correct. The test is only whether the opinion is grounded in a body of knowledge that is itself deemed reliable.
It would be for the trial judge to provide a reasoned decision on admissibility with reference to the criteria for assessing evidentiary reliability. Nevertheless, in determining whether expert scientific evidence is sufficiently reliable to be admitted, the Law Commission sees merit in an argument that the judge should exceptionally (that is, in cases where the evidence or field is particularly difficult) be permitted to call upon an independent assessor to provide assistance and guidance.
The Law Commission believes that judges (and criminal practitioners) should receive practical training on the methodology of science, the standards for determining the statistical significance of research findings and how to determine the reliability of experience-based expertise.
The Law Commission believes that if a system of non-compulsory accreditation of expert witnesses is encouraged, and the process of accreditation were to provide a further hallmark of reliability, there is no reason why the judge should not take into account, as an additional relevant consideration, the fact that an expert witness is or is not accredited when addressing the evidentiary reliability of his or her expert evidence.
Responding to the Law Commission Consultation
The consultation is open until 7 July 2009. The UK Register of Expert Witnesses will be conducting a number of surveys in the coming weeks to look at specific elements of these proposals. So, if you wish, you can wait to respond to these requests for specific input on issues whilst mulling over the broader implications of the proposals. Alternatively, if you want to respond straight away, you can:
• Respond in writing via the UK Register of Expert Witnesses. Please send responses by e-mail, post or fax by 19 June 2009 to:
Dr Chris Pamplin,
UK Register of Expert Witnesses,
11 Kings Court,
Tel: 01638 561590,
Fax 01638 560924
e-mail: [email protected]
• Respond in writing direct to the Law Commission. Please send responses by e-mail, post or fax by 7 July 2009 to:
11 Tothill Street,
Tel: 020 3334 0272,
Fax: 020 3334 0201
e-mail: [email protected]
• Or you can sign-in to the Law Commission’s on-line forum by visiting http://www.lawcom.org.uk/lc-forum/ and participate in a 'live' discussion.