Restricted Role of Expert Witnesses Confirmed

The High Court has recently reiterated the principle that an expert witness is there to assist the court in coming to its decision. In doing so, the expert may give their opinion solely on their area of expertise. It is not appropriate for them to address what the court is to decide, as doing so could undermine their role as an expert. Commercial Disputes partners, Gearoid Carey and Gerard Kelly examine this decision and its likely impact on future cases.

A recent High Court decision in the context of judicial review proceedings[1] has highlighted that expert witnesses are to give opinion evidence only in the area of their expertise. The court was at pains to stress that expert witnesses are not to decide the case and their duty to the court overrides any obligation to a paying party. The court was critical of experts in the case who it felt had served as a mouthpiece for their client and acted as advocates. Regarding one expert especially, the court felt that their strong views undermined their independence as an expert and justified the court attaching little weight to their evidence. Parties instructing experts therefore need to be clear with them as to their duties and role, ensure that the evidence they give is provided dispassionately and is limited strictly to their area(s) of expertise.

Background

The case here related to a dispute regarding the script system adopted for marking the written Mandarin Chinese leaving cert exam. Candidates were expected to use a script system known as simplified Chinese characters, in preference to traditional Chinese characters. However, the applicant maintained, among other things, that, because of his linguistic and cultural heritage - essentially Chinese in origin - where traditional characters were officially used, this was discriminatory and had no reasonable justification. Expert evidence on linguistics was put forward on behalf of both sides. The court ultimately took issue with the manner in which some of this expert evidence was provided.

The decision

The court began by noting that the principles relating to expert evidence had been set down by the Court of Appeal in Duffy v McGee[2] and from this Mr Justice Simons outlined the salient points, as follows:

• An expert witness is there to assist the court, not to decide the case
• The court has no obligation to accept the evidence of any particular expert, even if uncontradicted
• The duty of an expert to assist the court overrides any obligation to the party paying the expert’s fee
• The facts or assumptions on which the expert’s opinion is based should be stated and no material facts should be omitted from consideration, and
• The expert is to offer assistance by way of objective, unbiased opinion regarding their area of expertise and never adopt the role of advocate

In the latter regard, Mr Justice Simons commented that “[f]ar too frequently, expert witnesses appear to fundamentally misunderstand their role and wrongly regard themselves as advocates for the cause of the party by whom they have been retained”. In the current case, he noted that “regrettably” a number of the expert witness had “assumed the role of advocate and purported to express views on legal issues which are the exclusive purview of the High Court in these judicial review proceedings”. He noted, in particular, that one such witness had stated more than once that the marking scheme was “discriminatory and exclusionary”, while another had expressed the view that the refusal to mark answers in traditional characters was “unfair, discriminative and counterproductive”. These issues were, however, for the court to decide, not linguistics experts.

He went on to note that:

“The scope of issues in respect of which expert evidence is properly admissible in these proceedings is very narrow. The court requires assistance in understanding the practical distinction between simplified characters and traditional characters. The court also requires assistance in relation to the logistics of teaching and examining Mandarin Chinese by reference to one or other of the script systems. Thereafter, it is a matter for the court to assess whether, having regard to the evidence adduced by both sides, the policy choice to prefer simplified characters meets the legal standards applicable. i.e., proportionality and rationality.”

However, Mr Justice Simons was particularly critical of one expert witness. He stated that it was “apparent from the tendentiousness of her evidence that one of the applicant’s witnesses has very strong political views on the choice of script system.” Arising from that, he came to the view that such strong political views “undermines her independence as an expert witness on logistics and the court can attach little weight to her evidence.”

Conclusion

The decision reflects a useful re-statement of the principles applicable expert evidence as a matter of Irish law. It also demonstrates that, where an expert acts as a mouthpiece for their instructing party, and especially where political views are voiced, that can be fatal to the weight to be given to that expert’s evidence. It is important that when instructing experts practitioners are clear with them what is expected and required of them. It is also important to keep any expert instructed in check in terms of avoiding the expression of opinions outside of their area of expertise and to limit strong views which may be seen as political in nature. If there is a risk that the expert may stray beyond their expertise or become political in expressing their views, practitioners should also be clear with their clients as to the consequences of that happening. This will allow them to make an informed choice as whether to continue with the instruction of that expert.

For more information and expert advice on commercial disputes, contact a member of our Commercial Disputes team.

The content of this article is provided for information purposes only and does not constitute legal or other advice.

[1] B v Minister for Education & Ors [2024] IEHC 313

[2] [2022] IECA 254