Paragraph 6.78
Do consultees agree with our provisional proposal that there should be a statutory test for the admissibility of expert evidence in criminal proceedings, as follows?

(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.

Paragraph 6.79
Do consultees agree with our provisional proposal that trial judges should be provided with guidelines for determining the evidentiary reliability of scientific (or purportedly scientific) expert evidence, as follows?

(1) 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:

(a) 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;

(b) the margin of error associated with the application of, and conclusions drawn from, the principles, techniques and assumptions;

(c) whether there is a body of specialised literature relating to the field;

(d) 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;

(e) the expert witness’s relevant qualifications, experience and publications and his or her standing in the scientific community;

(f) 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

(g) whether there is evidence to suggest that the expert witness has failed to act in accordance with his or her overriding duty of impartiality.

Paragraph 6.80
Do consultees agree with our provisional proposed guidelines for experience-based (non-scientific) expert evidence, as follows?

(1) 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:

(a) the expert’s qualifications, practical experience, training and publications and his or her standing in the professional or other expert community;

(b) the extent to which the basis and validity of the expert’s opinion can be explained, with particular reference to:

(i) the extent to which the basis of the opinion (for example, any assumption relied upon) has been verified or discredited;

(ii) the specific instances which support the claim to experience-based expertise;

(iii) the bearing those instances have on the matter(s) in issue; and

(iv) whether the expert’s methodology or reasoning has previously resulted in a demonstrably valid or erroneous opinion;

(c) whether there is a body of specialised literature relating to the field of expertise and, if so:

(i) the extent to which it supports or undermines the expert’s methodology and reasoning; and

(ii) the extent to which the expert’s methodology and reasoning are recognised as acceptable amongst his or her peers;

(d) whether there is evidence to suggest that the expert has failed to act in accordance with his or her overriding duty of impartiality.

Paragraph 6.81
Do consultees agree with our provisional proposal that, where necessary, the party proposing to adduce expert evidence, whether the prosecution or a defendant, should have to demonstrate that it is sufficiently reliable to be placed before the jury?

Paragraph 6.82
Do consultees agree with our view that the other aspects of the present common law test governing the admissibility of expert evidence in criminal proceedings are satisfactory? (See below.) If so, do consultees believe that these rules should be codified in primary legislation?

1.2.1 whether the subject matter of the opinion is such that a person without instruction or experience in the area of knowledge or human experience would be able to form a sound judgment on the matter without the assistance of a witness possessing special knowledge or experience in the area

1.2.3 whether the witness has acquired by study or experience sufficient knowledge of the subject to render his opinion of value in resolving the issues before the court

1.3 A fourth requirement is that that the expert must be capable of providing an impartial opinion, in recognition of the fact that an expert’s overriding duty is to the court and not the party calling him or her to testify.

Paragraph 6.83i
We would also welcome consultees’ views on whether the trial judge should, in exceptional cases, be entitled to call upon an independent assessor to help him or her apply our proposed test for determining the reliability of expert evidence.

Paragraph 6.83ii
We would also welcome consultees’ views on whether the question of evidentiary reliability should always be decided before the jury is sworn, with the possibility of an interlocutory appeal to the Court of Appeal.

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