The function of expert witnesses came in for scrutiny in a recent High Court case and the court re-stated the boundaries experts must adhere to in giving their expert opinion.
The principle is 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. This principle was restated by the court in the case of B v Minister for Education & Others which came before the High Court by way of Judicial Review.
Background to the Case
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 court adopted the principles relating to expert witnesses that have been set down and adopted by the Court of Appeal in Duffy v McGee [2] 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 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,
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 current case, the judge found the experts had overstepped their role and he observed that:
“far 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.”
Referring specifically to the case before him, the judge said that “regrettably” a number of the expert witnesses 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.
This decision restates the law on the role of the expert witness and is critical of the role sometimes adopted by an expert witness who, in effect, acts as a mouthpiece for the side engaging the expert.
Expert witnesses should listen to the instructions of the solicitor retaining them and confine their evidence to their opinion of the matter in dispute based on their experience and qualifications.
B v Minister for Education & Others [2024] IEHC 313.
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