‘The principal weakness in the English law concerning the reception of expert evidence is that its development has been based on pragmatism rather than principle.’ (A Roberts, ‘Drawing on Expertise: Legal Decision Making and the Reception of Expert Evidence’ [2008] Crim LR 443, p 443).

Assess the validity of this observation in relation to criminal trials.

Analysis of the Question

The question is asking you to assess whether the common law approach to the admissibility of expert evidence is based on a consistent application of principle. You first need to define what would be a principled approach. One definition is suggested by Choo who (2021, p. 298) refers to the twin arguments of ‘necessity and reliability’ which underlie considerations of the admissibility of expert evidence. He points out that the first condition refers to the situations where the trier of fact cannot form an independent judgment without expert assistance. The second condition stresses that the law requires expect evidence to be sufficiently reliable to be admitted. In other words, such an approach sets out a coherent, rational test to apply in deciding whether expert opinion evidence should be admissible. The opposite of a stand based on clearly articulated principle is one based in ad hoc considerations, treating each case on its specific attributes.

Choo’s academic analysis could provide a framework for your essay, thus analysing the difference set out in the question, between pragmatism and principle. Your answer to this question would be improved if you were able to refer in the introduction to a number of miscarriages of justice which have been based on flawed expert evidence. These indeed demonstrate ‘weakness’ in that they do not uphold the principle of reliability. You should refer, as does Roberts (2008) to cases such as R v Cannings (2004) and the comments made in R v Kai-Whitewind (2005), para 85, that, ‘In Cannings there was essentially no evidence beyond the inferences based on coincidence which the experts for the Crown were prepared to draw.’ Hamilton v Post Office Ltd (2021) highlighted the dangers in an uncritical adoption of computer-generated data in hundreds of criminal prosecutions when reliable expert evidence should have drawn attention to the defects in the accounting software in the branch offices. You should set out arguments which criticise the current approach and those which point to its effectiveness. Note that the quotation refers to ‘reception’ of expert evidence so you should cover both admissibility and the treatment of evidence once it is admitted.

Arguments critical of the present approach i.e. the principles of necessity and reliability are not satisfied by current common law approach

• The Law Commission in its 2011 Report on Expert Evidence in Criminal Proceedings’ makes criticisms of the current common law approach and recommends that the trial judge should occupy more of a gate-keeper role. It recommended a statutory test for expert evidence. This proposal bears a close resemblance to the United States approach based on scientific reliability, see Daubert v Merrell Dow Pharmaceuticals (1993).
• The distinction between acceptable areas of expertise and ‘quack’ areas is unclear – see Robb (1991). Roberts (2008) is critical of the judgment in accepting voice identification evidence and suggests that the ‘relevance’ test is too vague. See also Luttrell [2004] on questionable expertise of the expert. It is arguable that necessity and reliability are not sufficiently distinguished and that the vaguer concept of relevance prevails.
• Gilfoyle [2001] – evidence helpful to the defence was excluded and subsequent investigations have shown this is a possible miscarriage of justice.
• Expert evidence is given too much weight by judge, counsel and jury who cannot assess it because it is beyond their competence – see Clark [2003] and Cannings [2004].
• The position on psychiatrists’ evidence is arguably inconsistent – compare the contrasting cases, Turner [1975] and Lowery [1975]. The courts have been slow in adopting a coherent approach to mental disability of defendants. See R v Wightman (1991).
• The cases are also incoherent on the ultimate issue rule e.g. DPP v A&BC Chewing Gum Ltd (1968) and also the question of diminished responsibility.
• The law on reception of evidence on credibility is unclear – see Weir (2006).
• The courts have in the past been criticised for being too partisan in relation to the police. In R v Ward (1993) the Court of Appeal stated that senior forensic scientists ‘regarded their task as being to help the police’.

Arguments to support current approach i.e. the principles of necessity and reliability is satisfied by the current common law approach

• The courts are adopting a liberal approach e.g. Stockwell [1993] and allowing more evidence. This accords with the principle of full proof and the judge can direct on weight and improper treatment if corrected on appeal e.g. Tilly [1981] where the Court of Appeal held the judge was wrong to invite the jury to make comparisons of handwriting without the guidance of an expert. This flexible approach in criminal law is fairer to defendants rather than the more structured cost-aware civil approach. See also R v Ward (1993) in relation to confession evidence where there are indications of abnormal personality disorder.
• The problem is lack of scientific understanding in the criminal justice system and the lay jury. See Edmond (2002) OJLS p53. He argues that there is an idealised view of scientific evidence, particularly by the appeal court. This could be addressed by exploring the conceptual disparity between the assessment of scientific evidence used to acquit and that used to convict.
• The main problem is inequality of arms and resources for forensic examination between defence and prosecution. It is this rather than inadequacy in the law which causes injustice.
• The current approach reflects popular values – e.g. scepticism about new sciences.
• The much-praised US approach is still led by case law and pragmatism prevails – e.g. Daubert (1993) replacing Frye (1923). There is academic support for the argument that the basic principles of the common law approach are correct. Ward (2013) CrimLR 561 argues that a radical overhaul is not needed.
• Some reform has been initiated. The Law Commission proposal for a statutory test has not been legislated. However, the government invited the Criminal Rules Procedure Committee to amend the relevant Criminal Procedure Rule, namely Rule 33. This retains the common law as setting the criteria for admissibility but now the courts may be expressly guided by the Law Commission’s proposals.
• It is utopian to rely on any one solution to this complex problem. Redmayne (2001, p92) argued that there are limitations on what can be expected of juries. Commenting on the reception of DNA evidence he writes: ’It would be nice if we could get jurors to appreciate the impact that a likelihood ratio of 200 million should have on their decision making but given the difficulty of getting them to quantify by prior odds, we should expect that they never will… Precision is and will remain beguiling, but its pursuit should not blind us to our limitations’.

Conclusion

You should comment on Roberts’ (2008) argument that more education is needed. See also House of Commons Science and Technology Committee Report, ‘the complexity and role of forensic evidence are ever increasing, and we have not seen evidence to reassure us that the criminal justice system has kept pace with these developments.' Arguably, the current position aids the prosecution; see Edmond (2002, p58) ‘Scientific evidence is an important component of most high profile miscarriage of justice cases.’ Note that the most elementary mistakes seem to have been made by the greatest legal brains. Consider how bench, counsel, and jury all were taken in by the elementary flaws in the statistics presented in the case of (Sally) Clark [2003]. Common sense and a healthy scepticism about received truths is an asset in the court room and the examination room.