Presented by Judge Malcolm Simmons, Belgrade 2018
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Role of the Expert Witness
The role of the expert is to assist the court make its decision.
Judge Malcolm Simmons explained that English textbooks often quote the succinct statement on the function of expert witnesses that Lord President Cooper gave in the Scottish case of Davie v Magistrates of Edinburgh, where he said:
“Their duty is to furnish the judge with the necessary scientific criteria for testing the accuracy of their conclusions, so as to enable the judge or jury to form their own independent judgment by the application of these criteria to the facts proved in evidence.”
The Lord President emphasised the court’s independent judgement. The court is not bound by the view of the expert.
Categories of Expert Evidence
That statement is written with a focus on the role of the expert in giving opinion evidence. However, one can distinguish between different categories of such evidence:
§ Expert evidence of opinion, upon facts adduced before the court;
§ Explicatory evidence — that is expert evidence to explain technical subjects or the meaning of technical words;
§ Evidence of fact, given by an expert, the observation, comprehension and description of which require expertise, if it is relevant to a fact in issue;
§ Evidence of fact, given by an expert, which does not require expertise for its observation, comprehension and description, but which is a necessary preliminary to the giving of evidence in the other four categories;
§ Admissible hearsay of a specialist nature. The reliance of an expert on, for example, medical textbooks and scientific works, or on the product of scientific teamwork, or on what a patient has told him or her, or on the opinions and reports of other experts who are not called as witnesses, means that hearsay evidence plays a much larger role in expert evidence than it does in the evidence of a non-expert witness. In order to give expert evidence an expert will often have to draw on reading materials within his or her discipline.
Judge Malcolm Simmons explained that experts can and often do give evidence of fact as well as opinion evidence. An expert witness, like any non-expert witness, can give evidence of what he or she has observed if it is relevant to a fact in issue.
Unlike other witnesses, an expert witness may also give evidence based on his or her knowledge and experience of a subject matter, drawing on the work of others, such as the findings of published research or the pooled knowledge of a team of people with whom he or she works. Such evidence also gives rise to threshold questions of admissibility, and the special rules that govern the admissibility of expert opinion evidence also cover such expert evidence of fact. There are many examples of a expert witnesses giving evidence of fact of that nature. For example, when an engineer describes how a machine is configured and works or how a motorway is built, he is giving expert evidence of factual matters, in which he or she draws on knowledge that is not derived solely from personal observation or its equivalent.
English Common Law
Judge Malcolm Simmons explained that it is common in English criminal trials for the misuse of drugs for the Crown to adduce the evidence of a policeman who has the experience and knowledge to describe the quantities of drugs that people tend to keep for personal use rather than for supply to others.
In Myers, Brangman and Cox v The Queen, an appeal from Bermuda, the Judicial Committee of the Privy Councilapproved of the use of police officers, who had special training and considerable experience of the practices of criminal gangs, to give evidence on the culture of gangs, their places of association and the signs that gang members used to associate themselves with particular gangs. In giving such factual evidence an expert witness can draw on the general body of knowledge and understanding in which he is expert, including the work and literature of others. The expert witness must set out his qualifications, by training and experience, to give expert evidence and also say from where he has obtained information, if it is not based on his own observations and experience.
There are also other roles for the expert in the court process beyond giving evidence. Parties often employ experts to give advice or to brief counsel on the preparation of a cross-examination without using them to give evidence. They can also assist the court in its preparation for a technical case.
It is the duty of the party that seeks to adduce the evidence of an expert to assess whether he or she has the necessary expertise and whether the evidence is admissible. The party instructing the expert must disclose to the expert all of the relevant factual material which was to contribute to the expert’s evidence, including material which did not support the client’s case. The expert should disclose in the written report the relevant factual evidence so provided.
“Before admitting the opinion of a witness into evidence as expert testimony, the judge must consider and decide two questions. The first is whether the subject matter of the opinion falls within the class of subjects upon which expert testimony is permissible. This first question may be divided into two parts: (a) 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 witnesses possessing special knowledge or experience in the area, and (b) whether the subject matter of the opinion forms part of 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. The second question is 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.”
Admissibility of Expert Evidence
Judge Malcolm Simmons explained that in Bonython the court was addressing opinion evidence. However, an expert witness can give expert factual evidence either by itself or in combination with opinion evidence.
In the recent case of Kennedy v Cordia (Services) LLP the Supreme Court suggested that there were four considerations that governed the admissibility of expert evidence. They were: First, whether the proposed expert evidence would assist the court in its task; Secondly, whether the witness has the necessary knowledge and expertise; Thirdly, whether the witness is impartial in his or her presentation and assessment of the evidence and Fourthly, whether there is a reliable body of knowledge and experience to underpin the expert’s evidence.
In Kennedy v Cordia (Services)LLP the Supreme Court found that while all four considerations apply to opinion evidence, when the first consideration (“assist the court”) is applied to opinion evidence the threshold is the necessity of such evidence. The four considerations also apply to expert evidence of fact, where the expert witness draws on the knowledge and experience of others rather than or in addition to personal observation or its equivalent.
‘Assisting’ the court
Judge Malcolm Simmons explained that it is for the court to decide whether expert evidence is needed, when the admissibility of that evidence is challenged. In R v TurnerLawton LJ stated:
“If on the proven facts a judge or jury can form their own conclusions without help, then the opinion of an expert is unnecessary.”
In Wilson v Her Majesty’s Advocate that also concerned opinion evidence, the High Court of Justiciary, in an opinion delivered by Lord Wheatley, stated the test thus:
“[T]he subject-matter under discussion must be necessary for the proper resolution of the dispute, and be such that a judge or jury without instruction or advice in the particular area of knowledge or experience would be unable to reach a sound conclusion without the help of a witness who had such specialised knowledge or experience.”
Most case law on, and academic discussion of, expert evidence has focused on opinion evidence to the exclusion of expert evidence of fact.
In Kennedy v Cordia (Services) LLP the Supreme Court found the test for the admissibility of expertevidence of fact cannot be strict necessity as, otherwise, the court could be deprived of the benefit of a expert witness who collates and presents to the court in an efficient manner the knowledge of others in his or her field of expertise. There may be circumstances in which a court could determine a fact in issue without an expert collation of relevant facts if the parties called many factual witnesses at great expense and thus a strict necessity test would not be met.
“If scientific, technical or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.”
Judge Malcolm Simmons explained that the advantage of the formula in this rule is that it avoids an over-rigid interpretation of necessity, where an expert witness is put forward to present relevant factual evidence in an efficient manner rather than to give an opinion explaining the factual evidence of others. If expert evidence of fact would be likely to assist the efficient determination of the case, the judge should admit it.
An expert must explain the basis of his or her evidence when it is not personal observation or sensation; “mere assertion carries little weight”, as the Lord President (Cooper) famously stated in Davie v Magistrates of Edinburgh.
In Davie the Lord President at p 40 observed that expert witnesses cannot usurp the functions of the jury or judge sitting as a jury.
In Pora v The Queenthe Judicial Committee of the Privy Council in an appeal from New Zealand, stated:
“It is the duty of an expert witness to provide material on which a court can form its own conclusions on relevant issues. On occasions that may involve the witness expressing an opinion about whether, for instance, an individual suffered from a particular condition or vulnerability. The expert witness should be careful to recognise, however, the need to avoid supplanting the court’s role as the ultimate decision-maker on matters that are central to the outcome of the case.”
Thus, while on occasion in order to avoid elusive language the expert witness may have to express his or her views in a way that addresses the ultimate issue before the court, expert assistance does not extend to supplanting the court as the decision-maker. The fact-finding judge cannot delegate the decision-making role to the expert.
The witness’s knowledge and expertise
Judge Malcolm Simmons explained that the expert witness must demonstrate to the court that he or she has relevant knowledge and experience to give either factual evidence, which is not based exclusively on personal observation or sensation, or opinion evidence. Where the expert witness establishes such knowledge and experience, he or she can draw on the general body of knowledge and understanding of the relevant expertise.
Impartiality and other duties
If a party proffers an expert report that on its face does not comply with the recognised duties of an expert witness to be independent and impartial, the court may exclude the evidence as inadmissible.
In Field v Leeds City Councilthe Court of Appeal upheld the decision of a district judge, who, having ordered the Council to provide an independent surveyor’s report, excluded at an interim hearing the evidence of a surveyor whom the Council proposed to lead in evidence on the ground that his impartiality had not been demonstrated.
The requirement of independence and impartiality is one of admissibility rather than merely the weight of the evidence.
In Kennedy v Cordia (Services) LLP the Court referred to the case ofThe Ikarian Reeferwherein it was stated that
“The duties and responsibilities of expert witnesses in civil cases include the following:
1. Expert evidence presented to the court should be, and should be seen to be, the independent product of the expert uninfluenced as to form or content by the exigencies of litigation.
2. An expert witness should provide independent assistance to the court by way of objective unbiased opinion in relation to matters within his expertise. An expert witness in the High Court should never assume the role of an advocate.
3. An expert witness should state the facts or assumption on which his opinion is based. He should not omit to consider material facts that could detract from his concluded opinion.
4. An expert witness should make it clear when a particular question or issue falls outside his expertise.
5. If an expert’s opinion is not properly researched because he considers that insufficient data is available, then this must be stated with an indication that the opinion is no more than a provisional one. In cases where an expert witness who has prepared a report could not assert that the report contained the truth, the whole truth and nothing but the truth without some qualification, that qualification should be stated in the report.
6. If, after exchange of reports, an expert witness changes his view on a material matter having read the other side’s expert’s report or for any other reason, such change of view should be communicated (through legal representatives) to the other side without delay and when appropriate to the court.
7. Where expert evidence refers to photographs, plans, calculations, analyses, measurements, survey reports or other similar documents, these must be provided to the opposite party at the same time as the exchange of reports.”
In Wilson v Her Majesty’s Advocatethe High Court of Justiciary quoted the first four duties and added the requirement that an expert witness “should in particular explain why any material relevant to his conclusions is ignored or regarded as unimportant.”
Reliable body of knowledge or experience
Judge Malcolm Simmons explained that what amounts to a reliable body of knowledge or experience depends on the subject matter of the proposed expert evidence.
In Davie v Magistrates of Edinburgh the question for the court was whether blasting operations in the construction of a sewer had damaged the claimants building and the relevant expertise included civil engineering and mining engineering.
In Myers, Brangman and Coxthe subject matter was the activities of criminal gangs; a policeman’s evidence, which was the product of training courses and long term personal experience as an officer serving with a body of officers who had built up a body of learning, was admitted as factual evidence of the practices of such gangs.
Can an employee of a party give evidence as an expert?
In Whitehouse v Jordan, the House of Lords appeared to suggest the apparent bias test was relevant to the admissibility of expert evidence, saying that expert evidence should be
“…seen to be the independent product of the expert, uninfluenced as to form or content by the exigencies of litigation”.
A similar view was taken in The Ikarian Reefer (№1), in which the High Court (Cresswell J) gave general guidance as to the duties and responsibilities of expert witnesses, repeating the same phrase quoted above.
These cases would suggest that relying upon employee-expert evidence is unwise, since it will leave the reliant party at the mercy of a court who is prepared to rule the evidence inadmissible for want of independence by virtue merely of their employee status.
However, in Field v Leeds City Council, the Court of Appeal (Lord Woolf MR) stated
“…if an expert is properly qualified to give evidence, then the fact that he is employed by [the defendant] would not disqualify him from giving evidence”.
May LJ confirmed that:
“…there is no overriding objection to a properly qualified person giving opinion evidence because he is employed by one of the parties”.
The key was said to be that the expert had
“…full knowledge of the requirements for an expert to give evidence before the court, and that he is fully familiar with the need for objectivity.”
Despite this approach being taken in Field, the court in Liverpool Roman Catholic Archdiocesan Trust v David Goldberg QC reverted back to the apparent bias considerations referred to in Whitehouse and The Ikarian Reefer.
Although initially (holding an application over to trial) Neuberger J at the pre-trial review commented that a close personal and professional relationship with a party did
“…not mean as a matter of law, or even as a matter-of-fact, that [the expert] is incapable of fulfilling the functions”
The High Court (Evans-Lombe J) disagreed, stating that any relationship between expert and party which might cause a reasonable observer to believe the evidence was unduly favourable to that party
“…his evidence should not be admitted however unbiased the conclusions of the expert might probably be”.
In R (Factortame Ltd and others) v Secretary of State for Transport, Local Government and the Regions (№2)Lord Philips MR concluded that Evans-Lombe J had (in Liverpool v Goldberg) applied the incorrect test to decide whether or not an expert witness should be permitted to give evidence. His Lordship found that applying an apparent bias test was wrong, and that the lack of an interest in the outcome of proceedings is not a precondition to the admissibility of evidence from the interested party.
Armchair Passenger Transport Ltd v Helical Bar Plc confirmed Factortame and Field as the law. With reference to Factortame, Liverpool v Goldberg, Field, The Ikarian Reefer and Whitehouse, the High Court (Nelson J) summarised the following principles as applicable to experts:
▪ It is desirable for there to be no actual or apparent interest in the outcome of proceedings;
▪ If there is an interest, including as an employee-expert, that does not automatically render the evidence inadmissible;
▪ The test of apparent bias is not relevant to the question of admissibility;
The test is
(1) Does the person have relevant expertise? If so,
(2) Is the person aware of, and willing/able to comply with, their primary duty to the court despite their connection to a party?
Gallaher International Ltd v Tlais Enterprises Ltd is a more recent confirmation that the law as summarized in Armchair represents the current law. Aikens J in the High Court held that an expert’s evidence was admissible, giving these four reasons:
▪ The expert’s employee-status had been openly declared;
▪ The terms of his engagement were set out in a letter, that had been disclosed, which made clear his primary duty to the court, and showed that the employer had done what it could to isolate him from the business while he was acting as expert;
▪ The expert’s report made clear that he understood his primary duty to the court, and was willing and able to comply with it;
▪ Independent experts in the field were scarce, such that it would be onerous and unfair to force the employer to find a new expert at a relatively late stage.
Weight of employee-expert evidence
Judge Malcolm Simmons explained that while employee-expert evidence is clearly admissible in principle, there remains the question of whether it is credible. That will depend on the circumstances (in particular, the nature of the employer/employee relationship and the size of the pool of suitable third-party experts), but while the courts are clear that they are unlikely to exclude employee-expert evidence, they are also clear that the weight to be attributed to such evidence is by no means invulnerable.
Aikens J in Gallaher recognised that an employee-expert’s independence is fair game in cross-examination and submissions, and that “The weight of his evidence may well be affected by the fact that he is employed by [a party]. That will be a matter for the trial judge to decide”.
Similarly, May LJ in Field, accepting the party’s employee’s expert evidence as admissible, remarked
“The fact of his employment may affect its weight but that is another matter”.
Nelson J in Armchair gave a candid warning:
“If the expert has an interest which is not sufficient to preclude him from giving evidence the interest may nevertheless affect the weight of his evidence…[and] If it transpires in this particular case that the weight to be attached to [the expert’s] evidence is found to be limited by reason of his connection with [a party] this will no doubt sound heavily in costs against [that party]”.
Judge Malcolm Simmons explained that the ECtHR has addressed on numerous occasions questions regarding the admissibility of expert evidence, its probative value and the extent to which they might rely upon it in its findings.
The Court has held that domestic rules on the admissibility of expert evidence must afford litigants the possibility of challenging it effectively.
Where an expert has been appointed by a court, the parties must in all instances be able to attend the interviews held by him or her or to be shown the documents he or she has taken into account; what is essential is that the parties should be able to participate properly in the proceedings.
Article 6 (1) of the Convention does not expressly require an expert heard by a “tribunal” to fulfil the same independence and impartiality requirements as the tribunal itself.
However, lack of neutrality on the part of an expert, together with his or her position and role in the proceedings, can tip the balance of the proceedings in favour of one party to the detriment of the other, in violation of the equality of arms principle.
Judge Malcolm Simmons explained that the parties must have a real opportunity to challenge the evidence of an expert called by a party or by the court in circumstances where lack of impartiality is clearly an issue.
A medical expert report pertaining to a technical field that is not within the judges’ knowledge is likely to have a preponderant influence on their assessment of the facts. In such circumstances it is an essential piece of evidence and the parties must be able to comment effectively on it.
The Convention does not bar the national courts from relying on expert opinions drawn up by specialist bodies that are themselves parties to the case where this is required by the nature of the issues in dispute.
The fact that an expert is employed by the same administrative authority that is a party to the case might give rise to doubts on the part of the applicant as the opposing party, but what is decisive is whether such doubts can be held to be objectively justified.
In DuskoIvanovski v The Former Yugoslav Republic of Macedonia the court relied upon an experts report prepared by the very government department that had initiated the criminal prosecution.
The ECtHR found the courts reliance on the experts report was not in breach of Article 6. However, the ECtHR did find a breach of Article 6 (3) (d) because the defendant was not given a real opportunity to challenge that evidence.
It is important to note that Article 6 (3) provides that “everyone charged with a criminal offence has the following minimum rights: (d) to examine or have examined witnesses against him and to obtain the attendance of witnesses on his behalf UNDER THE SAME CONDITIONS AS WITNESSES AGAINST HIM.
Judge Malcolm Simmons explained that the critical issue is the defendant must have a real opportunity to challenge the evidence against him whether in cross-examination or by calling a witness evidence.
In Constantinides v Greece the ECtHR found no breach of Article 6. The prosecution expert was not present in court and the defence did not have the opportunity to cross-examine her. However, the court referred to the fact the defendants own expert was in court and had challenged the conclusions of the prosecution expert through his evidence.
In Letinčić v. Croatia the ECtHR found as follows:
Article 6 (1) of the Convention places the “tribunal” under a duty to conduct a proper examination of the submissions, arguments and evidence adduced by the parties, without prejudice to its assessment of whether they are relevant to its decision. It thereby embodies the principle of equality of arms that, with respect to litigation involving opposing private interests, implies that each party must be afforded a reasonable opportunity to present his case — including his evidence — under conditions that do not place him at a substantial disadvantage vis-à-vis his opponent.
In the context of expert evidence, the rules on the admissibility thereof must not deprive the party in question of the opportunity of challenging it effectively. In certain circumstances the refusal to allow further or an alternative expert examination of material evidence may be regarded as a breach of Article 6 (1). In particular, where an expert has been appointed by a court, the parties must in all instances be able to attend the interviews held by him or her or to be shown the documents he or she has taken into account. What is essential is that the parties should be able to participate properly in the proceedings before the “tribunal”.
It should be also noted that Article 6 (1) of the Convention guarantees a right to a fair hearing by an independent and impartial “tribunal” and does not expressly require that an expert heard by that tribunal fulfill the same requirements.
However, the opinion of an expert who has been appointed by the relevant court to address issues arising in the case is likely to carry significant weight in that court’s assessment of those issues. In its case-law the Court has recognised that the lack of neutrality on the part of a court-appointed expert may in certain circumstances give rise to a breach of the principle of equality of arms inherent in the concept of a fair trial.
In Devinar v. Slovenia the ECtHRreferred to the case of Letincic and held as follows:
The Court further notes that (a) the position occupied by the experts throughout the proceedings, (b) the manner in which they perform their functions, and © the way the judges assess their opinions are relevant factors to be taken into account in assessing whether the principle of equality of arms has been complied with.
In this connection, the Court has found that the Convention does not bar the national courts from relying on expert opinions drawn up by specialised bodies to resolve the disputes before them when this is required by the nature of the contentious issues under consideration. What it does require, however, is that (a) the requirement of neutrality on the part of an appointed expert be observed, (b) that the court proceedings comply with the adversarial principle and that © the applicant be placed on a par with his or her adversary, namely the State, in accordance with the principle of equality of arms.
In particular, the Court has previously found that while the fact that an expert charged with giving an opinion on a matter in dispute is employed by the same administrative authority as that involved in the case might give rise to a certain apprehension on the part of the applicant, what is decisive is whether the doubts raised by appearances can be held to be objectively justified.
Judge Malcolm Simmons explained that it is for the Court to assess, having heard the evidence of the expert witness, whether the experts evidence was the independent product of the expert, uninfluenced as to form or content by the exigencies of litigation; that the parties were properly given the opportunity to challenge evidence presented to the court and there was real equality of arms. In other words: the process must be procedurally and substantively fair.
If an employee of a party could give evidence as an expert witness it follows that an employee of a party could also give evidence as a witness of fact or to produce documents before the court. However, if the purpose of calling the witness is simply to produce documents, it could be done by the prosecutor or by the party calling the witness.
 (1984) 38 SASR 45
  UKSC 6;  1 WL
 QB 834 at p 841
  JC 336
(1993) 509 US 579
1953 SC 34, 40.
Myers, Brangman and Cox at para 63.
 2 Lloyd’s Rep 68
atpara’s 59 and 60
 [6 October 2015] PC
 1 All ER 267
 2 Lloyd’s Rep 68
Times 14-Aug-2001, Gazette 23-Aug-2001,  EWHC Ch 396,  1 WLR 2337
Times 09-Jul-2002, Gazette 12-Sep-2002,  EWCA Civ 932,  3 WLR 1104,  QB 381,  3 Costs LR 467,  4 All ER 97,  BLR 1
Case No: CC/2002/PTA/0698Neutral Citation Number: 
Times 09-Jul-2002, Gazette 12-Sep-2002,  EWCA Civ 932,  3 WLR 1104,  QB 381,  3 Costs LR 467,  4 All ER 97,  BLR 1
 EWHC 464 (Comm)
Letinčić v. Croatia [3 May 2016]
Letinčić v. Croatia [3 May 2016]; Devinar v. Slovenia [22 May 2018]
 Sara Lind Eggertsdóttir v. Iceland; Letinčić v. Croatia
 Sara Lind Eggertsdóttir v. Iceland; Letinčić v. Croatia
Mantovanelli v. France [17 February 1997]; Storck v. Germany
Letinčić v. Croatia; Devinar v. Slovenia [22 May 2018]
Devinar v. Slovenia [22 May 2018]
 [24 April 2014]
 [6 October 2016]