Expert Evidence in Crime : An Update
The Law and Practice relating to Expert Evidence in criminal cases is changing. It can now conveniently be found in three primary sources:
¥ Stephen Hamilton v R  EWCA Crim 1555 (22nd July 2014);
¥ The Criminal Procedure Rules 2014 (laid before Parliament on the 25th June 2014 and coming into force on the 6th October 2014); and
¥ The Criminal Practice Directions Amendment No. 2 (published 23rd July 2014 and coming into force on the 7th October 2014).
The short headline is that even more case management is likely to result from the changes. Expert reports will have to contain more detail if admissions are not to be made. Courts are enjoined to achieve as much agreement as possible in advance, this time with the force of statutory instrument. The Practice Direction gives a checklist of factors for reliability. Recent experience suggests that it will become the first port of call in any argument about admissibility.
It is convenient to begin with the case of Stephen Hamilton. The defendant was charged with various cruelty and sexual offences relating to his daughter. The defence was that the allegations were unfounded and resulted from her mental illness. It was suggested that she may have recovered her memory during counselling or psychotherapy sessions in which case the reliability of her allegations might be affected. The defence were denied by the trial Judge the opportunity to call a Dr Boakes, a retired psychiatrist and psychotherapist, to comment upon the complainants account.
The Court of Appeal upheld the ruling, coming to the view that the critical issue which the jury had to resolve in the light of all the evidence was not only the credibility of X but also her reliability. It was, however, the responsibility of the jurors to undertake that task and not that either of the treating doctors or the defence expert.
At paragraph 26 the Court put the matter thus:
26. The fact of mental ill health, however, does not mean that the witness (in this case X) cannot accurately be describing what has happened to her or that it would prevent her from (or make her incapable of) being reliable in her account. These issues of fact are not for resolution by doctors but are to be determined by the jury: as Kay LJ put it in R. v Bernard V, (supra at para. 29), evidence is admissible when it is necessary:
to inform the jury of experience of a scientific and medical kind of which they might be unaware, which they ought to take into account when they assess the evidence in the case in order to decide whether they can be sure about the reliability of a particular witness.
The Court took the opportunity, however, to herald the forthcoming changes that will be brought about by the Practice Direction and the 2014 Rules. Thus it was said:
43. Before leaving an examination of the principles governing admissibility of this type of evidence, it is appropriate to note the general concern about expert witnesses. Whilst legislative reform has not been taken forward, following the Law Commission Report on Expert Evidence in Criminal Proceedings, there is real concern about the use of unreliable or inappropriate expert evidence. As a result, Part 33 of the Criminal Procedure Rules has been revised (with effect from 1 October 2014) and a new Practice Direction is to be published which will incorporate the reliability factors recommended by the Law Commission for the admission of expert evidence. The Advocacy Training Council, also, is in the course of preparing a tool kit for advocates to use when considering expert evidence and its admissibility, itself based upon the recommendations in the Law Commission Report.
44. When these changes occur, a new and more rigorous approach on the part of advocates and the courts to the handling of expert evidence must be adopted. That should avoid misunderstandings about what is (and what is not) appropriately included in an experts report and so either avoid, or at least render far more straightforward, submissions on admissibility such as those made in this case. In particular, as we have emphasised, comment based only on analysis of the evidence which effectively usurps the task of the jury is to be avoided: the task of the expert is only to provide assistance of the kind which Kay LJ articulated set out in para. 26 above.
The new rules have importantly created a new Rule 33.3 which requires the prosecution, as soon as is practicable after a not guilty plea, to serve a summary of the experts conclusions in any case where it wishes admissions of fact to be based upon any expert report. The defence in such a case have to respond within 14 days setting out which admissions will be made, and in the case of those that will not be made, what the disputed issues are.
The new Rule 33.4 requires a greater deal of information for any expert report that the prosecution which to rely upon other than by admission. Any report that it is wished to rely upon must now:
(a) give details of the experts qualifications, relevant experience and accreditation;
(b) give details of any literature or other information which the expert has relied on in making the report;
(c) contain a statement setting out the substance of all facts given to the expert which are material to the opinions expressed in the report, or upon which those opinions are based;
(d) make clear which of the facts stated in the report are within the experts own knowledge;
(e) say who carried out any examination, measurement, test or experiment which the expert has used for the report and –
(i) give the qualifications, relevant experience and accreditation of that person,
(ii) say whether or not the examination, measurement, test or experiment was carried out under the experts supervision, and
(iii) summarise the findings on which the expert relies;
(f) where there is a range of opinion on the matters dealt with in the report
(i) summarise the range of opinion, and
(ii) give reasons for the experts own opinion;
(g) if the expert is not able to give an opinion without qualification, state the qualification;
(h) include such information as the court may need to decide whether the experts opinion is sufficiently reliable to be admissible as evidence;
(i) contain a summary of the conclusions reached;
(j) contain a statement that the expert understands an experts duty to the court, and has complied and will continue to comply with that duty; and
(k) contain the same declaration of truth as a witness statement.
All of this is to ensure that reliability (so admissibility) can be assessed properly, and in accordance with the new Practice Direction, which provides a convenient yardstick for admissibility. Paragraph 33A.5 gives the criteria by which expert evidence should be judged, and Paragraph 33A.6, significantly, sets out a number of factors that should be taken into account in assessing weaknesses in any expert evidence.
The Practice Direction is not long and is set out in full for ease of reference.
The Practice Direction is as follows at Rule 33A:
33A.1 Expert opinion evidence is admissible in criminal proceedings at common law if, in summary, (i) it is relevant to a matter in issue in the proceedings; (ii) it is needed to provide the court with information likely to be outside the courts own knowledge and experience; and (iii) the witness is competent to give that opinion.
33A.2 Legislation relevant to the introduction and admissibility of such evidence includes section 30 of the Criminal Justice Act 1988, which provides that an expert report shall be admissible as evidence in criminal proceedings whether or not the person making it gives oral evidence, but that if he or she does not give oral evidence then the report is admissible only with the leave of the court; and Part 33 of the Criminal Procedure Rules, which in exercise of the powers conferred by section 81 of the Police and Criminal Evidence Act 1984 and section 20 of the Criminal Procedure and Investigations Act 1996 requires the service of expert evidence in advance of trial in the terms required by those rules.
33A.3 In the Law Commission report entitled Expert Evidence in Criminal Proceedings in England and Wales, report number 325, published in March, 2011, the Commission recommended a statutory test for the admissibility of expert evidence. However, in its response the government declined to legislate. The common law, therefore, remains the source of the criteria by reference to which the court must assess the admissibility and weight of such evidence; and rule 33.4 of the Criminal Procedure Rules lists those matters with which an experts report must deal, so that the court can conduct an adequate such assessment.
33A.4 In its judgment in R v Dlugosz and Others  EWCA Crim 2, the Court of Appeal observed (at paragraph 11): It is essential to recall the principle which is applicable, namely in determining the issue of admissibility, the court must be satisfied that there is a sufficiently reliable scientific basis for the evidence to be admitted. If there is then the court leaves the opposing views to be tested before the jury. Nothing at common law precludes assessment by the court of the reliability of an expert opinion by reference to substantially similar factors to those the Law Commission recommended as conditions of admissibility, and courts are encouraged actively to enquire into such factors.
33A.5 Therefore factors which the court may take into account in determining the reliability of expert opinion, and especially of expert scientific opinion, include:
(a) the extent and quality of the data on which the experts opinion is based, and the validity of the methods by which they were obtained;
(b) if the experts opinion relies on an inference from any findings, whether the opinion properly explains how safe or unsafe the inference is (whether by reference to statistical significance or in other appropriate terms);
(c) if the experts opinion relies on the results of the use of any method (for instance, a test, measurement or survey), whether the opinion takes proper account of matters, such as the degree of precision or margin of uncertainty, affecting the accuracy or reliability of those results; (d) the extent to which any material upon which the experts opinion is based has been reviewed by others with relevant expertise (for instance, in peer_reviewed publications), and the views of those others on that material;
(d) the extent to which the experts opinion is based on material falling outside the experts own field of expertise;
(e) the completeness of the information which was available to the expert, and whether the expert took account of all relevant information in arriving at the opinion (including information as to the context of any facts to which the opinion relates);
(f) if there is a range of expert opinion on the matter in question, where in the range the experts own opinion lies and whether the experts preference has been properly explained; and
(g) whether the experts methods followed established practice in the field and, if they did not, whether the reason for the divergence has been properly explained.
33A.6 In addition, in considering reliability, and especially the reliability of expert scientific opinion, the court should be astute to identify potential flaws in such opinion which detract from its reliability, such as:
(a) being based on a hypothesis which has not been subjected to sufficient scrutiny (including, where appropriate, experimental or other any testing), or which has failed to stand up to scrutible assumption;
(b) being based on an unjustifiable assumption;
(c) being based on flawed data;
(d) relying on an examination, technique, method or process which was he not properly carried out or applied, or was not appropriate for use in the particular case; or
(e) relying on an inference or conclusion which has not been properly reached.