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Duties of Expert Witnesses : Duffy v McGee T/A McGee Insulation and GMS Insulations Limited [2022] IECA 254

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By Rachel Lafferty, David Freeman & Julie-Anne Binchy


Published 18 May 2023


The judgment of the Court of Appeal in this case, delivered in November last year, was a strong reminder to expert witnesses and legal practitioners alike, of the strict parameters of role and responsibilities of an expert witness when engaged in litigation.

The proceedings involved a personal injuries claim brought by plaintiffs who claimed to have been exposed to toxic chemicals in their home following the spray of insulation at the premises. One of the central features of the appeal from the decision of the High Court, which we will focus on for the purposes of this article, was in relation to expert evidence and the duties of experts when giving their evidence to the Court.

Evidence of the expert acting for the defendant, Dr Thompson, had given rise to concern on the part of the High Court which found the evidence proffered by Dr Thompson could not be described as independent or unbiased. His specialism was in the space of toxicology, yet his report, among other matters, expressed views on legal issues and doctrines, questioned whether the plaintiffs were telling the truth and purported to give his opinion on psychiatric reports and medical reports which were exchanged, even though these areas were not within his discipline. The High Court proceeded to entirely exclude his evidence on this basis.

On appeal, Judge Noonan held that the High Court was correct to exclude the evidence, and found that the report prepared by the expert contained ‘red-flags’ and that the expert had seriously abused his position. The expert had also relied on two papers which the Court described as ‘industry generated’ and which had not been peer reviewed. The Court found the expert had made no attempt to consider any alternative scenario in respect of some strongly disputed facts, and simply took his clients’ instructions at face value. The Court held;

“I am satisfied the trial judge was perfectly correct to exclude Dr Thompson’s evidence in its entirety. There was in this case such an abject failure to comply with the most basic obligation of an expert, namely, to be objective and impartial, as to render all of Dr Thompson’s evidence inadmissible.”

Judge Collins delivered an additional short judgment, to add his own observations to the judgment delivered on behalf of the Court by Judge Noonan. He noted that expert evidence is often indispensable to the just resolution of civil proceedings but that experience demonstrates it is far from being an unalloyed blessing. Judge Collins referred to fact expert testimony may add to the duration of trials significantly, and noted there is often overlapping testimony at trial. He referred to Order 39, Rule 58(1) of the RSC which provides, “expert evidence shall be restricted to that which is reasonably required to enable the Court to determine the proceedings” and noted the rule gives extensive power to the Court to give directions in respect of expert evidence.

The judgment also engaged in discussion around the concept of reliability of material relied upon by the experts in their evidence, and noted that in the Irish jurisdiction there is no general requirement that expert evidence must meet any specific threshold of reliability as a condition of admissibility nor do the Irish Courts exercise a ‘gatekeeping’ function in that regard. Judge Collins did note issues of reliability will of course determine the weight to be given to evidence by the Court. Judge Collins concluding comments are stark and are worthy of note in concluding this article. He noted;

“[t]his is a disturbing case and it is certainly to be hoped that its like will not be seen again. As I have said, there needs to be a significant change of culture in this area. As well as the duties of expert witnesses themselves, I emphasis again the responsibilities of legal practitioners. The adverse consequences… may also have adverse consequences in costs. The Superior Courts have a broad jurisdiction to make costs orders against non-parties, if necessary…”

The case therefore serves not only as a reminder to expert witnesses as to the responsibilities and incumbent duties of their role, but also as a clear reminder to legal practitioners of their own responsibilities in their instruction of expert witnesses in litigation and the necessity for careful review of expert reports received. It will be interesting to see whether Judge Collins’ comments give rise to greater scrutiny by the judiciary of the experts engaged by parties to litigation, and indeed greater scrutiny of the material being relied upon by those experts following this decision, and the comments of the Court.

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