Recognising expertise in English civil litigation: Standards,experience and reliability

Abstract

In England and Wales the Civil Evidence Act 1972, s 3(1) provides that ‘where a person is called as a witness in any civil proceedings, his opinion on any relevant matter on which he is qualified to give expert evidence shall be admissible in evidence'. To be qualified to give expert evidence a witness must demonstrate knowledge or experience of some recognised field of expertise. The influential judgment in Barings plc v Cooper & Lybrand (2001) Lloyd's Rep. Bank. 85 states that this must be ‘a recognised expertise governed by recognised standards and rules of conduct'. On epistemological as well as doctrinal grounds, we endorse this requirement for recognised standards and/or rules as appropriate to most types of expert. It is less appropriate to witnesses whose expertise is based on experience of a particular trade or occupation. So-called ‘trade evidence' has caused particular difficulties in intellectual property cases. We argue that such evidence should be treated as expert opinion evidence, not evidence of fact or lay opinion, and should show some identifiable rigour in arriving at its conclusions, as well as conforming to the standards applicable to all expert witnesses.

Introduction

The admissibility of expert evidence in civil courts in England and Wales is governed by the Civil Evidence Act (CEA) 1972, s 3(1), which provides that ‘where a person is called as a witness in any civil proceedings, his opinion on any relevant matter on which he is qualified to give expert evidence shall be admissible in evidence’. By s 3(3) ‘“relevant matter” includes an issue in the proceedings in question’, so that s 3 has the effect of abolishing the common-law ultimate issue rule in civil proceedings. ¹ Following the advice of the Law Reform Committee (1970, para. 19), whose proposals it enacted, the CEA says nothing more about what being ‘qualified’ as an expert entails. Evidence that is admissible under s 3 is subject to the power and duty of the court to restrict it to what is ‘reasonably required’, ² and the judicial ‘gatekeeping function’ is exercised largely at that stage.

What it is to be ‘qualified’ and what amounts to opinion evidence which only a qualified witness can give, have nevertheless become important and difficult questions in the law of civil evidence in England and Wales. These issues have been particularly problematic in relation to so-called ‘trade evidence’ in intellectual property cases, both because it is difficult to say who is ‘qualified’ and because some courts evade that issue by classifying evidence that they want to admit as either evidence of fact or admissible non-expert opinion. The latter part of this article will examine this type of evidence in some detail. What it is to be ‘qualified as an expert’ must, we argue, be interpreted flexibly enough to allow trade evidence to be given as expert evidence where it is genuinely useful, but strictly enough to ensure that the evidence meets basic standards of intellectual rigour.

The importance of recognised standards

The starting point of our analysis is the principle set out in a much cited passage from Evans-Lombe J's judgment in Barings plc v Cooper & Lybrand:

expert evidence is admissible under section 3 of the Civil Evidence Act 1972 in any case where the Court accepts that there exists a recognised expertise governed by recognised standards and rules of conduct capable of influencing the Court's decision on any of the issues which it has to decide and the witness to be called satisfies the Court that he has a sufficient familiarity with and knowledge of the expertise in question to render his opinion potentially of value in resolving any of those issues. Evidence meeting this test can still be excluded by the Court if the Court takes the view that calling it will not be helpful to the Court in resolving any issue in the case justly. ³

Barings was a first instance judgment, but Evans-Lombe J's analysis was adopted in the Court of Appeal decision in esure v Direct Line. ⁴ The court in esure was highly critical of the use of a ‘branding expert’ to establish matters that the judge (or the Hearing Officer who decided the case at first instance) was capable of deciding for himself. Although strictly obiter, because the Hearing Officer had not relied on the disputed evidence, the court's remarks gave a strong steer to judges to exclude the kind of evidence that would fail the Barings test.

It is our view that the Barings test is essentially correct, and applies to most, but not all, expert evidence. Let us briefly explain the argument in theoretical terms before proceeding to a doctrinal analysis of the English case law.

We draw here on Sanford Goldberg's (2018) work in social epistemology. Social epistemology is epistemology that recognises, to a greater extent than traditional epistemology, the extent to which we all rely on others – on co-operative social practices – to acquire knowledge about the world. Goldberg's account stresses the importance of the normative expectations people have of one another to play their epistemic roles. These expectations include the expectations courts have of witnesses in general and of expert witnesses. Witnesses in general can be expected to rely on their senses and memory, but only insofar as those apparent perceptions and memories form part of a coherent account of the world. (This is, roughly, Goldberg's ‘coherence-infused reliabilism’.) And people whose role is to take part in some specialised epistemic practice, like accountancy or forensic science, or for that matter tarot-card reading, can be expected to abide by the standards of those practices.

When a practice is, as Goldberg puts it, legitimate (in a way that tarot-card reading probably is not), the practices that participants follow are conducive to their giving reliable information about matters within their domain. Moreover, there are practices for checking how far those standards (or methods) are conducive to reliability, some of which are summarised in the famous Daubert judgment (peer review, quantifying error rates, etc.). ⁵ When a practice is of this kind, a court has a basis both for believing testimony that has been prepared in accordance with the practice, and for critically assessing it according to how far the witness (or others whose work the witness relied on) have adhered to the relevant standards, and how far any departure from those standards undermines their conclusions. An expert witness is expected to explain how they have followed relevant standards, and if their evidence on this point is not truthful, they may face severe sanctions for contempt of court, ⁶ or even perjury.

While the epistemic role of standards is a central reason for expecting expert witnesses to base their evidence on a standard-governed practice, there are two types of evidence where the significance of shared standards is different. In some cases, the standards themselves, and whether or not they have been adhered to, are the subject matter of the evidence. This is common in cases of professional negligence, of which Barings was an example, but esure was not. The evidence to which the Barings test was applied in esure was ‘a series of assertions’ from a branding consultant about the likelihood of confusion between two trade marks. ⁷

The second type of case is where the expert is relying on extensive experience in order to say what people typically do or say in certain situations – the size of packages in which drug dealers in a certain town sell drugs, ⁸ or the factors that influence consumers in choosing certain products. In such cases there may be no professional standards to be followed in acquiring and analysing the relevant evidence. If the witness has been selling clothes and incidentally observing how consumers react to certain information, there is probably no professional standard that governs the making of those observations.

This does not mean that there are no standards that witnesses can legitimately expected to follow in giving such evidence. If someone has extensive experience of certain situations, and they have reason to believe that those experiences are broadly representative of a larger class of such situations, they are entitled to draw a generalisation about the larger class of situations. Generalisations of this sort are, we submit, quite clearly evidence of opinion – although, as we shall see, courts sometimes try to avoid this conclusion. A witness can give factual evidence, for example, that ‘I have seen this operation done hundreds of times, but this is the only time I have seen the surgeon do it in this way.’ But a generalisation such as ‘this method is almost never used in this type of surgery’ is an expert opinion – an inference from what the witness has personally observed (and/or read) together with a belief or assumption that those observations are representative of practice in the field. In order to be able to assess the weight of this evidence, the court needs a clear explanation of the observations on which it is based, the frequency or rarity of the relevant behaviour in the cases observed, and the reasons for believing that the observations are (or might not be) representative of a class of cases which includes the case at hand.

In cases of this type – including the ‘trade evidence’ cases which we discuss below – the Barings test is not exactly apposite, because the standards or rules to be applied are not those of a particular specialism, but rather standards and rules (such the Civil Procedure Rules (CPR) Part 35 and accompanying Practice Direction) that apply to any expert witness.

To accommodate such cases, Barings can be subsumed under a broader and vaguer test, which is expressed in sufficiently general terms to apply to all expert evidence. The South Australian criminal case of R v Bonython, cited in Barings ⁹ and numerous other English judgments, calls for ‘a body of knowledge or experience which is sufficiently organized or recognized to be accepted as a reliable body of knowledge or experience, a special acquaintance with which by the witness would render his opinion of assistance to the court.’ ¹⁰ There can hardly be an ‘organized body of knowledge’ without rules or standards of some kind that determine whether a proposition counts as part of the ‘body’, but this is not true of a ‘body of experience’. In Kent v Apple Inc, the Competition Appeals Tribunal held that:

The modern hurdle for admissibility does not require an ‘organised branch of knowledge’. The question is what qualifications or experience the particular person has to satisfy us that we are able to treat their evidence as deriving from a recognised expertise with some identifiable rigour in both their knowledge and their approach. ¹¹

From the examples given in the judgment it appears that in this case what gives the expertise ‘identifiable rigour’ is ordinary inductive reasoning, for example from ‘a range of assignments’ as a consultant in an industry to some ‘patterns apparent’ in the industry, or from ‘wide and deep experience’ to a statement about ‘invariable practice’. ¹² The phrase ‘some identifiable rigour’ neatly captures what was missing from the purported expert evidence in esure, but it allows for the possibility that in some cases the necessary degree of rigour may be identified by the court even though it does not consist of following the standards of an established form of expertise.

Combining Bonython and Kent, we can draw a distinction between an ‘organised body of knowledge’ and a ‘recognised body of experience’ and say that Barings provides a test for the former and Kent for the latter. This is also consistent with Kennedy v Cordia, where the UK Supreme Court reviewed the Scottish law on skilled (expert) evidence in civil cases. ¹³ In Kennedy, which, given the ‘commonality of approach’ remarked on by the Supreme Court, is of significant persuasive authority in England and Wales, the Bonython test is simplified to the question ‘whether there is a reliable body of knowledge or experience to underpin the expert's evidence’. ¹⁴ By itself this is unhelpfully vague, but it is consistent with applying Barings to a ‘body of knowledge’ and an ‘identifiable rigour’ test to inferences drawn from experience. Without ‘some identifiable rigour’ a body of experience cannot reliably ‘underpin’ an expert's conclusions.

An even vaguer formulation than Kennedy's can be found in the Chancery Guide:

expert evidence is generally limited to opinion evidence of a suitably qualified expert. Permission for such evidence is only given where the court is satisfied that there is a sufficiently recognised body of expertise on which to draw and that the court would be assisted by such evidence in determining one or more issues in the proceedings. (Courts & Tribunals Judiciary, 2023, [9.3])

There is no explanation of what ‘sufficiently recognised’ means, and it seems possible that this bland form of words was adopted because of uncertainty over whether there was any settled test for admissibility.

To summarise, we can draw a distinction between three types of expert evidence in the civil (including family) courts. In the first, the ‘standards and rules of conduct’ are part of the subject matter of the expert evidence, and the expert's role is to assist the court in applying the relevant standards to the facts of the case. In the second type, there are recognised standards and/or rules about how experts should conduct their inquiries and formulate their opinions. The third type of evidence is given by witnesses whose claim to expertise rests on their ability to generalise from a series of experiences gained in the course of their work, rather than on any systematic observation or analysis to which recognised rules or standards apply. Such experience may constitute a ‘recognised body of expertise’ but the relevant ‘rules and standards’ can only be those that apply to all expert witnesses under the Civil Procedure Rules (CPR), Practice Directions etc. The three sections that follow discuss these three types of evidence in turn.

Standards and rules as subject matter

The first category of expert evidence is the one with which the Barings case was concerned, as were most of the authorities reviewed by Evans-Lombe J. Though esure shows that the ‘standards and rules of conduct’ test is not applicable only to cases of this type, there is no doubt that it is in relation to these cases that Barings has the greatest weight as a persuasive precedent, and it is mostly in similar cases that it has been followed.

As Foskett J has observed, the test in Barings would better summarise the earlier authorities if it referred to ‘standards and/or rules of conduct’. ¹⁵ In one of the most significant of those earlier cases, Oliver J explained:

The extent of the legal duty in any given situation must, I think, be a question of law for the court. Clearly, if there is some practice in a particular profession, some accepted standard of conduct which is laid down by a professional institute or sanctioned by common usage, evidence of that can and ought to be received. But evidence which really amounts to no more than an expression of opinion by a particular practitioner of what he thinks that he would have done had he been placed, hypothetically and without the benefit of hindsight, in the position of the defendants, is of little assistance to the court; whilst evidence of the witnesses’ view of what, as a matter of law, the solicitor's duty was in the particular circumstances of the case is, I should have thought, inadmissible, for that is the very question which it is the court's function to decide. ¹⁶

The objection to evidence of the duty owed as a matter of law would be better expressed by saying, not that it is the very question that the court has to decide – that objection having been removed by the CEA 1972 ¹⁷ – but rather that as English law is not a matter to be proved by evidence at all, evidence that does no more than state a view of the law is irrelevant.

Where a field is governed by rules and/or standards they must be ‘relevant to the matter the court has to decide’. ¹⁸ In Re RBS, Hildyard J found that equity analysts were trained experts who had to meet certain standards and many of whom belonged to an Institute with a Code of Conduct, but those standards were not relevant to the question of what information a company needed to make available to investors. ¹⁹

Where the rules applicable to the relevant conduct exist in some codified form, the role of the expert is somewhat analogous to that of an expert on foreign law. It is not only to tell the court what rules have been promulgated, but also how they are interpreted in practice by the community whose activities they regulate. ²⁰ For example, in a case where the claimant was injured by an opponent in a rugby match, two rugby referees gave evidence as to how the ‘laws’ of the game and the ‘principle of fair play’ applied to various incidents that had been recorded on video. ²¹

Where there are no codified rules, standards may be ‘sanctioned by common usage’. ‘Sanctioned’ means something more than ‘generally followed’. In Farol Holdings Ltd v Clydesdale Bank plc ²² the issue was whether a bank's conduct was unfair within the meaning of the Consumer Credit Act 1974. One element of this analysis was whether the conduct of the defendant in ‘adding hidden basis points to the fixed rate offered to customers for the purpose of meeting internal targets’ ²³ fell below the standard of commercial conduct reasonably expected of banks. The court held that ‘sanctioning an accepted practice’ involved ‘something significantly more than evidence as to what was usual practice among banks’ ²⁴ and further that something being usual practice did not necessarily mean it was fair. In other words, a usual practice is not the same thing as a normatively expected standard of conduct, and the latter was what needed to be shown in this case.

In Vilca v Xstrata, dealing with the actions of security staff responding to protests at a mine in Africa, Foskett J said that there must be an ‘established consensus’ about what was ‘good practice in the kind of situation that arose in this case’; there was perhaps an ‘emerging consensus’ but that did not suffice. ²⁵

Standards or rules conducive to reliability and objectivity

The test of whether a specialism has recognised standards and/or rules of conduct has been applied not only to witnesses testifying about the standards of those professions, but as a criterion for identifying recognised and reliable fields of expertise. Phonetics, ²⁶ optometry ²⁷ and economics ²⁸ have been held to satisfy the test, and it has also been treated as applicable to digital forensics. ²⁹ Evidence from specialists in opinion polling has been excluded as failing to meet the test, in part because membership of their professional association was open to anyone who paid the required fee – hardly a standard that guaranteed reliability. ³⁰ On the other hand, in the same judgment (part of the infamous ‘Plebgate’ libel case) where the court admitted the phonetics and optometry evidence, an ‘expert in forensic virtual reconstructions’ was held to be qualified within the meaning of CEA 1972, s 3, without any consideration of the standards or rules applying to his discipline, on the ground that he possessed ‘considerable expertise, recognised by courts on a number of occasions’. ³¹ Forensic reconstruction is a branch of digital forensics which might well pass the Barings test, if only because there are rules and standards for correctly using the appropriate specialised software (Flor, 2011); but Mitting J seems to have thought it unnecessary to look at the standards of a method that was frequently relied on in the criminal courts as a way of visually representing crime scenes.

The Barings test is, in our view, appropriate to most forms of expert evidence governed by the Civil Procedure Rules (CPR). Wherever the CPR apply, an expert report must contain a statement of truth which includes the words: ‘The opinions I have expressed represent my true and complete professional opinions on the matters to which they refer.’ ³² An identical requirement applies to expert reports in family proceedings. ³³ A ‘complete professional opinion’ is one that takes account of all relevant evidence and which, where more than one view is tenable from the perspective of the relevant profession, indicates that fact. ³⁴ To determine what is relevant and what is a tenable opinion requires some sort of common standard as to what information is relevant to an opinion and how inferences are to be drawn from it. ³⁵ In the absence of some such shared standard it is hard to see how anyone can be qualified to express a ‘professional opinion’, although in some cases, such as Kent v Apple, ³⁶ the standard may be one set by the court rather than by a particular profession.

So-called ‘connoisseur’ testimony is no exception. To be a connoisseur one must have some awareness of what was called in Re Pinion (which concerned the artistic merit of certain paintings and furniture) ‘an accepted canon of taste’, ³⁷ although like other experts a connoisseur may depart from the consensus if they give cogent reasons for doing so. If connoisseurship in the field of, say, perfumes, is simply a matter of being able to recognise scents, then there must be some implicit standard of what counts as sufficient ability for connoisseurship, or suitable preparation for a ‘sniff test’ ³⁸ (see Bernstein, 2008; Crump, 2003).

The perfume sniffer is one example of an expert with knowledge and experience of a putatively reliable method for assessing some matter relevant to the case at hand. Wherever a recognised method exists, there must be some standard that determines what constitutes a correct application of the method. Moreover, to establish that the method is reliable, there must be some recognised standard of reliability and some recognised procedure for establishing whether a method meets that standard or not. Therefore, it is implicit in the Bonython and Kennedy criteria that a field of knowledge characterised by some recognised standards and/or rules of conduct must exist in every case where an opinion purports to be based on the application of a reliable method (other than ordinary inductive reasoning), as well as in cases where those rules or standards are part of the subject matter of the evidence.

A central example of evidence based on putatively reliable methods is that of forensic scientists whose activities are regulated by the Forensic Science Regulator. Although it is most familiar in criminal cases, forensic science evidence of various kinds (e.g., about handwriting, the causes of fires, or digital forensics) ³⁹ is also used in civil cases. The Forensic Science Regulator Act 2021, s 4, provides for the Code of Practice published by the Regulator to be admissible in criminal and civil proceedings in England and Wales and to be taken into account in resolving any question. Clearly, therefore, the Code is admissible as evidence of the rules and standards applicable to forensic science. To help the courts in considering questions of admissibility, the Code requires experts who admit that their evidence is non-compliant in some way to furnish a statement of what steps they have taken to mitigate the effects of non-compliance. ⁴⁰ Such a statement may enable the court to decide that the evidence is sufficiently rigorous and reliable to be admitted despite a breach of the Code.

Of course, it cannot be assumed that every body of specialists that organises itself as a profession (using that term to embrace any self-regulating and self-certifying group of specialists: see Abbott, 1988) will in fact produce reliable knowledge. For example, there appears to be a degree of consensus among astrologers about the standards to be followed in casting horoscopes (Groome and Roberts, 2014: 64), but that tells us nothing about whether horoscopes are reliable guides to personality or future events. This highlights the need for the standards/rules of a body of expertise to include procedures for assessing its reliability, which do not depend solely on self-assessment by practitioners (Ward, 2006).

Generalising from experience

The third type of expert evidence includes what the US evidence scholar Michael Risinger (2000: 511) calls ‘summarizational’ evidence. This is evidence from witnesses who have extensive experience of particular subject matter, and who, rather than describe particular experiences in detail, draw generalisations from an entire body of experience. Examples are witnesses who have worked for a long time in a particular business and who can give evidence about common or typical practices in that business, without referring to or applying established rules or standards; and police officers who generalise from their observations of particular types of criminal activity. Such witnesses may also draw on what they have been told by others, such as police informants and fellow officers. Treating them as experts allows such hearsay evidence to be admitted as part of the ‘body of expertise relevant to [their] field’. ⁴¹

In Kennedy v Cordia, Lords Reed and Hodge identified a similar category of evidence given by ‘a skilled witness who collates and presents to the court in an efficient manner the knowledge of others in his or her field of expertise’. ⁴² Such evidence should, they said, be classed as ‘skilled evidence of fact’, which need not be subjected to the strict test of ‘necessity’ which they found to be applicable to opinion evidence in Scots law. ⁴³ In English civil cases (except family law cases), expert evidence, whether of fact or opinion, may be admitted if it is ‘reasonably required to resolve the proceedings’, even if it is not absolutely necessary. ⁴⁴ Nor has strict necessity ever been a requirement for admissibility in English criminal law. ⁴⁵ The word ‘needed’ in the Criminal Practice Directions has a similar meaning to ‘reasonably required’ and refers to the principle in Turner ⁴⁶ that juries and judges do not need experts to tell them what they are presumed to know already. The Scottish case of Wilson v HM Advocate ⁴⁷ seems to us to have done no more than affirm the same principle, and it is unfortunate that the Supreme Court interpreted it as setting a strict necessity test, which it then sought to relax by designating some expert evidence as factual.

Fortunately, English courts are not bound to follow Kennedy down this murky path. The classification of summarisational evidence as ‘fact’ is unconvincing. The point of such evidence is not for the witness to relate his or her experience, using generalisations as a convenient way to shorten the presentation, but rather to infer from that experience a generalisation, for example about practices in a particular trade, that can be applied to the circumstances of the case at hand (Risinger, 2000: 512–3). The question is then whether the expert has sufficient data to draw a conclusion which can reliably be applied to the facts of the case – and that generalisation is opinion evidence if anything is.

A good illustration of this point is Clarke v Marlborough Galleries, ⁴⁸ where the artist Francis Bacon's executor sued his gallery over agreements made in 1958 and 1964 in London. A proposed expert witness had experience of negotiating such agreements but in New York, during a much later period, and for reasons of confidentiality could not reveal the basis of his opinion that Bacon could and should have got a better deal. The judge was not satisfied that this constituted ‘a reliable body of knowledge and experience’ on which to base an opinion about a different market at a different period. What happened in the New York art market might be a question of fact, but its only relevance was as the basis for an opinion about the art trade in general.

An indication of what will constitute a reliable body of experience can be found in the Privy Council case of Myers v R. The witness:

must have made a sufficient study, whether by formal training or through practical experience, to assemble what can properly be regarded as a balanced body of specialised knowledge which would not be available to the tribunal of fact… But care must be taken that simple, and not necessarily balanced, anecdotal experience is not permitted to assume the robe of expertise. ⁴⁹

Myers was a case about a police officer gathering intelligence about gangs. As he had received specialised training on this from the FBI, ⁵⁰ it is arguable that he was in fact applying recognised standards in his field of knowledge in systematically recording intelligence gathered by his colleagues and himself. From the earlier case of R v Hodges, ⁵¹ approved in Myers, it appears that a more ad hoc method of gathering information will suffice, and this must be true of witnesses who are simply reporting their experiences of working in a particular trade. Such witnesses cannot be expected to record their experiences systematically in case they are ever called to give evidence about them, but like any expert witness they should be expected to set out clearly the facts on which they rely, how far those facts are within their direct knowledge and the inferences that they draw from them. ⁵²

The same test can be applied to witnesses who might not fall into the category of ‘summarisational’ experts but who have built up an extensive body of knowledge without formal training. One of our reviewers raised the fictional example of Mona Lisa Vito, played by Marisa Tomei in the film My Cousin Vinnie. She has no formal qualifications whatever, but by working in her father's garage has built up an encyclopaedic knowledge of the characteristics of various cars, from which she deduces that only one model could both have made the tyre tracks at a crime scene and been mistaken by eyewitnesses for the car driven by the defendants. In English law her lack of qualifications would not preclude her being an expert, ⁵³ and there can be little doubt (in view of the prosecution expert's response to her testimony) that she has ‘a balanced body of specialised knowledge which would not be available to the tribunal of fact’.

In Declan Colgan the claimant wished to call evidence about the state of the market for streamed music at the time the relevant contract was made. The defendant accepted that such evidence would be admissible, but as evidence of fact and not as expert evidence within the scope of CPR 35. ⁵⁴ The purpose of this submission seems to have been to confine the evidence to strictly factual matters, ⁵⁵ and to insist that any inferences as to the issues in the case, such as what would have been apparent to the parties at the time of the contract, were matters for the judge. The issue was discussed in considerable detail by Deputy Master Henderson, who concluded that CPR 35 would cover ‘expert evidence of fact’ which drew on the witness's experience and the work of others in the field, as well as ‘expert evidence of opinion as to facts given by the expert drawing on the general knowledge and understanding in which he is an expert’. ⁵⁶ Such evidence would be admissible if it would assist the court (following Kennedy v Cordia) ⁵⁷ and was ‘reasonably required’ under CPR 35.1. Barings did not apply to this type of evidence (which was of the third type we have identified). On the material before him the learned Deputy Master considered that although the evidence would assist the court it was not ‘reasonably required’ given its cost (it is beyond the scope of this article to discuss the ‘reasonably required’ point in detail).

With regard to the expert evidence of fact, the Chancery Guide explicitly states that where part of the expert's evidence is relied on to establish primary facts, it should ‘be incorporated into a factual witness statement to be exchanged in accordance with the order for the exchange of factual witness statements. The purpose of this practice is to avoid postponing disclosure of a party's factual evidence until service of expert reports’ (Courts & Tribunals Judiciary, 2023: [9. 12]).

This enables evidence of primary fact from an expert to be dealt with at an earlier stage for procedural reasons but does not in our view impact on the expert evidence of both fact and opinion properly covered by CPR35.

‘Trade evidence’

Our third category of admissible expert evidence, that where there is not an established body of rules and standards but where the expert can draw generalisations from a body of experience with some degree of rigour, encompasses ‘trade evidence’ in intellectual property disputes, to the extent that it is based on real expertise that can assist the courts. Unfortunately, the approach of the courts to this type of evidence is inconsistent. Too often, evidence of very dubious probative value is admitted as evidence of fact, and therefore outside the scope of CPR Part 35, when in our view it should be treated as opinion evidence which does not cross the threshold of expertise.

Intellectual property actions encompass a significant range of cases and can involve a wide variety of expert evidence (Lambert, 2018). The type which concerns us here is that described in a number of intellectual property cases as ‘trade evidence’. There does not appear to be an exact definition of this widely used term, which has been applied both to independent witnesses and those connected to the parties. The four areas in which it appears most used are: (1) the likelihood of confusion of the average consumer pursuant to s 10(2) of the Trade Marks Act 1994 (TMA); (2) whether a competing mark takes unfair advantage of or is detrimental to the distinctive character or repute of a registered trade mark pursuant to s 10(3) TMA, which ‘demand[s] a consideration of what a customer will think when he or she sees a particular word or sign’ ⁵⁸ ; (3) the acquired distinctiveness of a trade mark, being its recognisability as a designator of origin by a significant proportion of the relevant public, which can relate to its validity; and (4) whether a misrepresentation of a connection between the defendant and claimant is likely to deceive the relevant public, which is a necessary element of a passing off action. All these issues involve an assessment of the perception of the consumer in the industry in question in each case.

The state of the law concerning the introduction of trade evidence is encapsulated in Fenty v Arcadia Group Brands Ltd (t/a Topshop) ⁵⁹ as summarised in Phipson (Malek, 2024: paras. 33–89):

Birss J summarised the case law and principles in relation to trade evidence:

Trade witnesses may give evidence of ‘the circumstances of the trade’ and ‘nature and circumstances of [the] market’, even including expressions of opinion as to the likely behaviour of market participants, without this amounting to expert evidence under CPR Part 35.

This is so even though such witnesses will explain and rely on their experience in the trade ‘in order to justify their evidence and add credibility to it’.

Deciding whether evidence given by a trade witness amounts to expert evidence ‘cannot be done’ without close examination of the evidence itself in the context of the issues in the proceedings. ⁶⁰

However, a witness who expresses an opinion on the ultimate question before the court – for example, in Fenty, whether the relevant public will think that a photograph of the pop star Rihanna on a T-shirt means that the T-shirt is licensed or authorised by Rihanna – is expressing an expert opinion and needs to comply with CPR Part 35. ⁶¹

Fenty concerned a claim for passing off. The defendant (which operated retail fashion stores) sold T-shirts bearing a clear image of the claimant Rihanna. Simply using an image on a T-shirt does not give rise to a cause of action in itself, there is no ‘image right’ under English law. The action based on passing off required in this case, inter alia, a misrepresentation by the defendant, likely to deceive a substantial part of the relevant public, that the claimant had endorsed the T-shirt in question. This could not be assumed by virtue of the mere use of the image but had to be established on the particular facts of the case.

As the Fenty case shows, this approach gives the judge a very broad discretion to decide what should or should not be treated as expert evidence. By making it difficult to decide in advance what will or will not be deemed to constitute expert evidence, it runs a risk that litigants will take a chance by introducing evidence of opinion based on little or no rigorous analysis, in the hope that it will be deemed to be non-expert evidence which escapes regulation under CPR part 35. Such evidence may waste considerable time both for witnesses and the court, even if it is ultimately excluded on case management grounds (as seems to have happened to some of the witnesses in Fenty) and, at worst, it may unduly influence the judge's decision.

In Fenty the evidence given by some of the trade witnesses went well beyond proof of fact, or the kind of non-expert opinion envisaged by CEA 1972 s3(2), where a witness who ‘is not qualified to give expert evidence’ states an opinion as a way of conveying relevant facts personally perceived by him in an economical way (‘he seemed very angry’, for example). Statements from trade witnesses such as ‘I know from direct experience that fans believe there is a direct connection between the celebrity and the merchandise which bears their name, image or artwork’ and ‘Fans want and expect T-shirts with an image of the artist to be authorised’, ⁶² which do not appear to be based on any ‘direct experience’ of being a teenage pop fan, are not only statements of opinion about consumers’ typical mental states but come very close to opining on the ‘ultimate issue’: namely whether consumers of the T-shirt in question were likely to be deceived by the use of Rihanna's image into believing there was an authorised link between Rhianna and the outlet selling the T-shirt. Such statements are admissible only as expert opinion evidence under CEA 1972, s 3(3).

In order to assist the court in assessing its weight, such evidence ought to comply with the requirements of CPR 35 and in particular the requirements for reports set out in the Practice Direction, such as ‘setting out the substance of all facts and instructions which are material to the opinions expressed in the report or upon which those opinions are based’ and acknowledging any range of opinion on the matters dealt with in the report. ⁶³ Any responsible witness should include these matters in their evidence, but some may not do so without an explicit rule requiring it. It is difficult to see why being subject to Part 35 should exert any ‘chilling effect’ if the evidence really is of value and merits admission.

While not all areas of expertise are governed by specific standards or rules of conduct, or are underpinned by an ‘organised body of knowledge’, ⁶⁴ a coherent body of expertise remains necessary, together with a clear understanding of the proposed expert's position within, and knowledge of, that expertise. This is supported by the Kent, Kennedy and Myers cases discussed above. ⁶⁵

In Kent, the defendants challenged the admissibility of expert evidence in relation to the app industry and the payment systems industry, arguing that the ‘Class Representative has failed to establish that a recognised expertise governed by recognised standards and rules of conduct exists in relation to either industry.’ ⁶⁶ The Class Representative drew the court's attention to a paragraph from Hodgkinson and James (2020) which argues, with specific reference to trade experts, that ‘the phrase “recognised expertise governed by recognised standards and rules of conduct” will have to be interpreted in a broad way if it is to reflect the modern practice of the English civil courts.’ ⁶⁷ As noted above, the Competition Appeals Tribunal concluded that the ‘modern hurdle for admissibility does not require an “organised branch of knowledge”’, but the expert must have sufficient qualifications or experience to satisfy the court that their evidence derived from ‘a recognised expertise with some identifiable rigour in both their knowledge and their approach’. ⁶⁸

By contrast, the judgment in Fenty fails to identify any element of rigour that would ensure the reliability of the evidence. To use the Privy Council's words in Myers, the court failed to draw the crucial distinction between ‘a balanced body of specialised knowledge’ (albeit not one ‘organised’ according to the standards of a formal discipline) and ‘simple, and not necessarily balanced, anecdotal experience’. ⁶⁹

The consideration of the admissibility of the trade evidence in Fenty involved a detailed hearing. Following this hearing, although found to be admissible as trade evidence, the evidence of two of these witnesses was not relied upon, as it was found to be US-centric and duplicative of other evidence. The remaining trade evidence, given by a witness who ran a brand licensing agency and describing the state of the brand licensing business, was found to not be of any material assistance: ‘it was much too generalised and unspecific to be of any value and I will place no weight on it’. ⁷⁰ Birss J had considered, because the case related to a particular segment of the market, ‘T-shirts aimed at young teenage girls’, that the court would be assisted by ‘proper evidence focusing on the nature and circumstances of the market’. However, despite the time and costs involved in the preparation and consideration of this evidence, this aim does not appear to have been fulfilled.

Fenty can be contrasted with the detailed decision on the admissibility of evidence in Glaxo Wellcome UK Ltd (t/a Allen and Hanburys) v Sandoz. ⁷¹ At an earlier hearing the defendant had sought to adduce expert evidence from three experts. Although the claimant appeared to agree that the topics to be covered by the suggested expert evidence needed to be addressed, they contended that ‘it was both possible and preferable for those topics to be addressed through the medium of factual evidence, and in particular evidence from “trade” witnesses, that is to say, witnesses in the relevant professions speaking from their own personal knowledge’. ⁷² The Master agreed, and therefore declined permission to adduce expert evidence.

Against this background, the statements of three eminent clinical academics relied on by the claimant were challenged by the defendant on the basis that they were expert evidence, for which no permission had been given. A number of additional trade witnesses (doctors and pharmacists) proposed to give their views on what others, such as patients or pharmacists, might do or think, as evidence of the likely deception of the relevant public (in this case in relation to passing off and asthma inhalers).

In a thorough and well-reasoned judgment Arnold J (as he then was) considered each statement and determined, in relation to three clinical academics put forward as trade evidence, that for the most part, the evidence to be given was expert witness evidence: ‘Put simply, they are documents authored by experts, expressing their experience and opinions as experts.’ ⁷³ In relation to the claimant's reliance on ‘the fact that the witnesses all refer to their personal experience as supporting the contention that this is trade evidence’ the judge stated:

I do not accept that submission. Any expert witness will rely, among other things, upon their own experience in the field in question as supporting the conclusions which they draw. That is precisely what these witnesses do. It is not at all the same thing as a witness speaking to their own personal knowledge and their own personal actions in a narrative manner. That is not what these witnesses have done. It is a fallacy to suppose that expert evidence is limited to the expression of opinions. Expert evidence, as has often been held, includes evidence which on its face is expressing a fact. If it requires expertise for the person in question to be able to state that fact, it is expert evidence. That is what in many places these witnesses are doing. ⁷⁴

In relation to the other witnesses that were accepted as ‘trade evidence’ following the Master's ruling, the defendant contended that significant elements of their statements strayed beyond the evidence that trade witnesses can give, namely factual evidence based on their personal knowledge and experience. The claimant argued that any element of opinion in their evidence as tendered sat within CEA 1972, s 3(2).

Again, the judge considered these statements in detail and allowed factual evidence that which was clearly based on personal experience but not that which strayed, in particular, into views of what customers or pharmacists would think or do, which was deemed inadmissible as opinion and/or speculation. He noted the difficult line as to the extent to which ‘trade witnesses can express views based on their own personal experience as to what other people would or would not do’, allowing one GP's statement that ‘Based on my experience I think other GPs and pharmacist [sic] would make the same assumption’ as himself about certain matters as ‘just about on the right side of the line’ in relation to other GPs but not to pharmacists, although he was ‘dubious as to whether this is really admissible and of weight’. ⁷⁵

Arnold J also had to consider several statements given by Glaxo witnesses and to a large extent accepted the defendant's arguments that elements of these statements were commentary on documents and/or expert opinion evidence for which there was no permission and/or speculation on the ultimate question and therefore inadmissible.

The preparation of all these statements, the arguments between the parties on the topic and the hearings themselves will have incurred significant time and cost. The matter could have been better dealt with by a more tightly controlled decision at an earlier stage in the proceedings which made clear the distinction between admissible factual evidence from the trade and reasonably required expert evidence, setting out what was permissible in each area.

By contrast, an example of evidence drawing on ‘personal knowledge…in a narrative manner’ is another of Arnold J's decisions, Enterprise Holdings, Inc v Europcar Group Ltd, ⁷⁶ where branch managers from the claimant gave evidence about ‘incidents of confusion which they and their staff had experienced…and the reasons which consumers had expressed to them for being confused.’ ⁷⁷ The judge treated this as evidence of fact, noting that ‘a few passages…shaded into expressions of opinion’, which it would have been ‘easy enough’ for the court to ignore. ⁷⁸

A trade witness should be capable of stating their industry experience and expertise in detail and then either drawing conclusions from it by explicit reasoning or simply narrating relevant experiences so that the court can draw its own conclusions. Mere assertions about the likelihood of confusion, etc., or opinions which are ‘simply argument’ ⁷⁹ without a foundation in factual evidence at best can be fairly dismissed as ‘empty rhetoric’ ⁸⁰ or as the Supreme Court put in Kennedy v Cordia, ‘worthless’. ⁸¹ As the future Arnold LJ observed about the evidence of three trade journalists in Vibe Technologies Ltd’s Application, ⁸² which related to the acquired distinctiveness of a trade mark, ‘in so far as they are speaking to the perceptions of their readers, none of them explains the basis upon which they are able to do so’; ⁸³ the judgment referenced the Hearing Officer's view that ‘views from the trade’ could not be substituted for ‘actual evidence’ of the perceptions of consumers. ⁸⁴ The importance of clarity on the status of trade evidence is further borne out by the treatment of Ms Perez's witness evidence in Fenty as described in the Court of Appeal decision. ⁸⁵ Ms Perez was described as the main witness for the claimants but also as having experience in the merchandising side of the business and making statements about that trade. ⁸⁶ Birss J in essence treated what this witness said as argument, articulating the claimant's case.

The Court of Appeal found, however, that in one respect Birss J had ‘focused on an expression of opinion by Mrs Perez having earlier ruled that it was argument and not something that needed to be cross examined to’. The court concluded that the judge's conclusion was nonetheless sound, so it did not need to ‘embark on a consideration of whether and to what extent evidence of trade practice, trade usage, consumer behaviour and consumer perception constitute expert evidence’. ⁸⁷ This is somewhat of a missed opportunity to bring consistency to this area and this example illustrates the danger that denoting opinion evidence as argument and/or allowing it to be adduced as evidence of fact will lead to its being given the kind of weight that is only properly due to well-founded expert opinion

Evidence ‘reasonably required’

Although this article has not discussed the ‘reasonably required’ test in detail in relation to expert evidence in general, it is such an important issue with regard to trade evidence that some discussion is called for.

In Guccio Gucci SpA v Paolo Gucci, ⁸⁸ (which related to passing off and trade mark infringement in the designer label market), Sir Nicolas Browne-Wilkinson said that while the decision was his, he did not understand why he, who was not a buyer of designer goods and knew nothing of those buyers’ habits, ‘should be required to make that decision on the basis of my own lack of information, rather than on the basis of expert advice from those who can tell me what the experience in that market is’. ⁸⁹ On the other hand, when the goods are those normally sold to the general public, the question of likelihood of confusion in a trade mark case or likelihood of deception in passing off is a ‘jury question’, ⁹⁰ one to be decided from the perspective of the average consumer, about which the judge is capable of forming their own view. In these circumstances the view of a trade expert on the likelihood of a consumer being confused or deceived is not necessary or reasonably required and should not be admitted. This includes evidence of whether two marks are confusingly similar. ⁹¹ This may be different if the markets in question are ‘are ones with which the judges are unfamiliar’ as in Fenty. ⁹²

Hasbro Inc v 123 Nahrmittel GmbH ⁹³ is a good example of when expert evidence could sensibly have been excluded as not being ‘reasonably required’. The case concerned, inter alia, a claim for infringement of the claimant's mark PLAY-DOH by the defendant's tagline ‘THE EDIBLE PLAY DOUGH’. This required the court to consider the impact of the words in question on the average consumer. The court considered that ‘play dough’ did not relate to a specialist market and that whether the use of a sign referring to ‘THE EDIBLE PLAY DOUGH’ was likely to confuse consumers or took unfair advantage of, or was detrimental to the distinctive character or repute of the claimant's trade mark, was a ‘jury question’. ⁹⁴ The parties were each permitted to call an expert witness but Floyd J considered that all the points they made were ones on which a judge could form his own view without expert evidence.

Six trade witnesses gave evidence, ostensibly of fact, for the claimant about the different products in the market. This case was cited in Fenty as a good example of trade evidence being introduced effectively and kept in its proper place without being treated as expert evidence. Whilst this evidence appeared helpful to a degree in setting out certain factual circumstances of the market in question, e.g. the use of the term ‘play dough’, the volume of evidence appears excessive, and some witnesses strayed into opinion evidence marked by a distinct lack of rigour. For example, one witness described the defendant's dough as looking ‘like a “cheap copycat product”’. Floyd J found it ‘difficult to see how a powdered dough mix could be described as a copy of a pre-mixed dough. Ms Pearce did not explain why she thought it was a copycat product, except that she did not like the packaging.’ ⁹⁵

Hasbro cited the Economist case ⁹⁶ and its discussion of trade evidence, which notably it badged as expert evidence:

The function of an expert witness is to instruct the judge of those matters which he would not otherwise know but which it is material for him to know in order to give an informed decision on the question which he is called on to determine. It is legitimate to call evidence from persons skilled in a particular market to explain any special features of that market of which the judge may otherwise be ignorant and which may be relevant to the likelihood of confusion. It is not legitimate to call such witnesses merely in order to give their opinions whether the two signs are confusingly similar. They are experts in the market, not on confusing similarity.

Enterprise (referring to Fenty) stated in relation to trade evidence:

Such witnesses are often retailers: they may be retailers of the claimant's goods or the defendant's goods or sometimes both. Such witnesses can give factual evidence as to the circumstances in which the relevant goods are sold, the characteristics of the consumers who purchase them and any instances of apparent confusion the witnesses (or their staff) have experienced. There is a controversial and difficult question as to whether such witnesses can go further and express opinions as to the likely reactions of customers to a particular sign, which involves consideration both of whether such evidence is expert evidence subject to CPR Part 35 and whether, even if it is not expert evidence, it can properly be admitted or given any weight in cases involving ordinary consumer goods and services. ⁹⁷

This may be a controversial question, but it is not a very difficult one. Plainly, these witnesses are giving opinion evidence, and if they arrive at their opinions by generalising from their experience of the trade, it is expert evidence. But it is evidence that generally adds little or nothing of value when a case concerns ordinary consumer goods and services.

It may be true that trade evidence is ‘much less costly overall’ than survey evidence (as intimated in Fenty), although as we have seen, trade evidence can be extensive and costly, but the question is why ‘costly survey evidence of little probative value’ needs to be replaced by other evidence at all. ⁹⁸ In Enterprise, Arnold J stated, following Interflora ⁹⁹ that ‘in a case concerning ordinary consumer goods and services, the court is able to put itself into the position of the average consumer without requiring expert evidence or a consumer survey.’ Like Lewison LJ in Interflora, he cited Chadwick LJ's statement in BACH and BACH Flower Remedies Trade Marks ¹⁰⁰ :

The task for the court is to inform itself, by evidence, of the matters of which a reasonably well informed and reasonably observant and circumspect consumer of the products would know; and then, treating itself as competent to evaluate the effect which those matters would have on the mind of such a person with that knowledge, ask the [relevant] question. ¹⁰¹

Enterprise involved an array of seemingly costly survey evidence relating to the acquired distinctiveness of the claimant's mark, which is notoriously difficult to prove. Arnold J accepted the survey evidence as ‘confirmatory of the conclusion which I would in any event be minded to reach in the light of all the other evidence in the case’. ¹⁰² Given the difficulty of proving acquired distinctiveness, survey evidence may be helpful or even essential in some cases, but this requires careful consideration on the facts.

Arnold LJ's judgment in Lidl Great Britain Ltd v Tesco Stores Ltd ¹⁰³ (discussed below) confirms that surveys may be of assistance when considering acquired distinctiveness but of much less assistance with likelihood of confusion, and that care must be taken over their admission in alignment with the statements in Interflora ¹⁰⁴ and the guidelines set out by Whitford J in Imperial Group Ltd v Philip Morris & Co. ¹⁰⁵ In Arnold LJ's view, expert evidence other than that of market researchers interpreting surveys ‘is expensive, but it is likely not to be probative. … It is very doubtful whether it is possible to find anyone who is an expert on likelihood of confusion, for example. An experienced Chancery judge will almost certainly have more expertise on that question than any so-called expert.’ ¹⁰⁶ He states that ‘evidence of the shopping habits of consumers’ may be useful as evidence, not in itself of confusion, but ‘of circumstances giving rise to a likelihood of confusion’, with the example given being ‘whether they are in the habit of reading the label on an item before selecting it for purchase or whether they simply rely upon the appearance of the packaging’ and in some cases ‘evidence of this nature can properly be given by means of factual evidence from a witness with experience in the relevant trade’, as per Fenty. ¹⁰⁷

He also suggested that the evidence of ‘real consumers’ could be helpful, not because they were necessarily representative of the average consumer but because the court could make its own inference as to whether the confusion (or absence of it) they experienced was indicative of how consumers in general were likely to react. ¹⁰⁸ Therefore, a clear assessment is necessary as to what evidence is required in a given case, its status and how it is to be presented and trade evidence is not necessarily an appropriate or necessary substitution for survey evidence.

Summarisational evidence

The recent case law on trade evidence affords clear examples of summarisational evidence being inappropriately treated as fact rather than opinion. Both Fenty and Lifestyle Equities CV v Royal County of Berkshire Polo Club Ltd ¹⁰⁹ adopt a wide interpretation of when an opinion is being given by a witness who is not qualified to give expert evidence to convey relevant facts personally perceived by the witness in question and therefore coming within the Civil Evidence Act 1972, s 3(2). For example in Lifestyle, Señor Garcia, who was the first defendant's Latin American agent, ¹¹⁰ gave a very detailed witness statement on the market for branded polo goods together with his views on the reasons for the appeal of the defendant's brand to customers. His statement, for example, that ‘[t]his is a crowded market…in the Lat Am Territories and these brands co-exist with each other well without customer confusion’ was found to be an opinion given as a way to convey relevant facts perceived by him, ¹¹¹ the weight of which could be determined at trial in the light of cross-examination. According to Mellor J, the facts ‘personally perceived’ Sr Garcia ‘include at least that (a) there are numerous other polo brands in these markets, (b) these brands appear to co-exist without problems, (c) he has not encountered any consumer confusion between these polo brands and (d) he has had sufficient contact with the market to be in a position to perceive these facts’. ¹¹² If (b) is stretching the category of ‘facts personally perceived’ to the limit, (d) is stretching it past breaking point. The claim that he has observed the market sufficiently to be able to make generalisations such as (b) is an opinion that constitutes Sr Garcia's claim to be an expert. Some such claim is always implicit in summarisational evidence that draws generalisations from personal experience, and it identifies this type of evidence as expert evidence.

Lifestyle Equities is by no means unique in stretching s 3(2) in this way. ¹¹³ In our submission, where evidence of this kind is genuinely valuable (as Sr Garcia's may well have been), it should admitted under consistent principles from witnesses qualified to give expert evidence.

By contrast, Lidl v Tesco is a case where the judge at first instance kept the ostensibly factual evidence within reasonably strict bounds; ¹¹⁴ but it is surprising that a consumer researcher, Ms Marks, was treated as giving factual evidence when she explained the ‘tests’ which her company used when conducting research for Tesco on the proposed Clubcard Prices logo. Although the tests were clearly designed to allow the researchers to draw inferences from the pattern of consumer responses, Ms Marks’ explanation of the results was treated by the judge primarily as part of a factual narrative about how Tesco came to adopt the logo. ¹¹⁵ Tesco had relied on an expert in an earlier application dealing with the two surveys, but Smith J had not found this report convincing in that application, ¹¹⁶ and Tesco did not rely on this report at the trial. When it came to drawing inferences from the test that supported one party's case or the other's, Smith J pointed out that Lidl's witness was tendered as an expert, whereas Ms Marks, for Tesco, was not. Partly for this reason, she preferred the evidence of Lidl's witness. ¹¹⁷ The lack of expert evidence on their side appears to have contributed in some measure to Tesco losing the case, despite Lidl's claim being one that sat ‘at the outer boundaries of trade mark protection and passing off’. ¹¹⁸

While we do not suggest that the Lidl v Tesco case itself is an instance of ostensibly factual evidence getting out of hand, it shows the unsatisfactory state of the law. The objection to Ms Marks giving opinion evidence was not that she was unqualified to do so, but that Tesco had not obtained leave to adduce expert evidence from her. Under CEA 1972, s 3, if a witness of fact who is ‘qualified to give evidence as an expert’, gives opinion evidence falling within their expertise, it is admissible as expert evidence. The judge could have stopped the witness giving such evidence because permission for it had not been obtained under CPR 35, but having allowed it to be given, it seems somewhat unfair to discount it as expert evidence, given that Ms Marks seems to have been appropriately qualified.

We suggest that a detailed exploration of this topic should take place in the Court of Appeal as the way the boundary between factual and expert evidence is drawn appears neither sound not consistent. While it might be technically permissible to treat the inferences drawn by someone in Ms Marks's position as factual evidence about what a party knew or believed, it creates difficulties when the parties seek to draw wider inferences from the same evidence. It would surely have been preferable for Ms Marks to be classed as an expert and the weight of her evidence evaluated accordingly.

It should not be difficult to find experts in a necessary field as suggested in Lidl (including those capable of giving evidence of the special features of the market or substantiated opinion on customer behaviour or perception), even if their expertise is, to adopt Arnold LJ's rather fine distinction, in the factors that may lead to confusion, rather than in determining whether confusion is likely. As we have argued, an expert need not always represent a profession with established standards but they should be able to substantiate their view with some ‘identifiable rigour’ ¹¹⁹ and explain its basis in light of their experience and expertise within the parameters of CPR 35. This should not be unduly onerous. The requirements of CPR 35 are there for good reasons, including: to ensure it is correct to give such a potentially weighty role to the evidence; to deal with any issues of partiality which may arise with witnesses both connected and unconnected to the parties; to understand clearly the instructions given and questions asked of that witness; and any range of opinion that may exist in the area which could be important. Complying with part 35 should also help to ensure that such evidence is treated consistently with other expert evidence of fact and opinion evidence in other cases.

In conclusion, our view is that trade evidence should be used cautiously, with due consideration being given as to whether this specialist knowledge is reasonably required in the case in question, and whether the evidence goes beyond proof of fact or s3(2). In these circumstances the evidence should be treated as expert evidence with the backing of the necessary body of evidence, mitigating any concerns as to partiality and uncertain weight to be attached to the evidence, providing a consistent approach and potentially ultimately saving time and costs.

Conclusion

We have argued that the Barings test, with its focus on the rules or standards adopted by specialised communities of experts, is appropriate in most cases to determine whether someone is ‘qualified to give expert evidence’. It identifies the main reason why experts drawn from the professions, sciences and other specialised fields of knowledge are regarded as trustworthy: because they follow standards which in the case of many such specialisms can reasonably be assumed to be conducive to objectivity (in that those following the standards correctly will tend to arrive at the same opinion) and reliability. There are, however, important areas of expertise which rely on experience – being in the right places at the right times over an extended period to make a large number of relevant observations – rather than on any rigorous and standardised method for analysing such experience. That does not mean that such experts escape any requirement for rigour in their analysis; it means, rather, that the requirements of rigour are those that apply to all expert witnesses. At a minimum, they should set out clearly the nature of the relevant experience (e.g., what features of consumer behaviour have they observed, in what settings, and, perhaps very approximately, how many examples) and the process of reasoning by which they draw any conclusions from those observations.

We can summarise our view of what it is to be ‘qualified to give expert evidence’ by expanding slightly the four points listed in Kennedy:

(i) the evidence must assist the court (if it does not, no-one is qualified to state such an opinion in evidence), and must do so to such a degree as is ‘reasonably required’;

(ii) the witness must have the necessary knowledge and experience, i.e., that described in point (iv);

(iii) the witness must be able and willing to be impartial as required by their overriding duty to the court;

(iv) there must be ‘a reliable body of knowledge or experience to underpin the expert's evidence’.

We contend that a reliable body of knowledge is a body of knowledge produced by people following certain recognised standards which are conducive to reliability. It may also comprise knowledge of the standards or rules of conduct followed by a members of a given profession or occupation. A reliable body of experience is one that is sufficient, in quantity and in the balance between different types of relevant experience, to form the basis for reliable generalisations or judgments. The making of such generalisations or judgments need not be governed by standards or rules pertaining to the specific form of expertise, but must be based on rigorous analysis and conform to the standards and rules applicable to all expert witnesses. Expert evidence should not be allowed to escape those standards and rules by being reclassified as evidence of fact.