Reigning in the Experts: High Court Reiterates the Boundaries for Expert Witnesses

In a recent ruling, the High Court in B v Minister for Education & Ors,[1] emphasised the essential principle that an expert witness’ primary duty is to assist the Court by providing opinions strictly within their area of expertise. This article written by Ian Middleton, Solicitor, CKT and Elena O’Driscoll, Trainee Solicitor gives an overview of this decision and its potential impact on future cases.

Background

This case involved Judicial Review proceedings challenging the legality of the marking scheme for the written Mandarin Chinese Leaving Cert exam. The Plaintiff’s legal team relied heavily on expert testimony from linguistic experts to support their claim.

The High Court’s Ruling

The Court criticised the evidence presented, underscoring that an expert’s role is to assist, not to decide, and their duty to the court outweighs any obligation to the party who pays their fees. The Court highlighted a concern that some experts appeared to act as advocates, expressing strong views that compromised their independence, resulting in their evidence being given little weight.

The High Court reaffirmed principles from an earlier decision in Duffy v McGee,[2] in which the Court of Appeal found that an expert had overstepped by expressing opinions on legal matters and psychiatric injury, areas beyond their expertise.

Presiding over the Judicial Review case, Judge Garrett Simons emphasised several critical points regarding the scope of expert testimony:

1. An expert witness is there to assist the Court, not to decide the case. Moreover, the Court is not obligated to accept any expert’s evidence, even if it remains unchallenged.
2. An expert’s duty to assist the Court overrides any obligation to the party paying their fees.
3. Experts must clearly state the facts or assumptions underlying their opinions, without omitting any material facts, and
4. Experts should provide objective, unbiased opinions in their area of expertise and should avoid acting as advocates.

Justice Simons criticised several experts in the case who assumed the role of advocate, expressing legal conclusions such as “discriminatory and exclusionary” which he stated were beyond their remit.

The decision reinforces that the scope for expert evidence in court proceedings is often limited to areas where technical or specialised knowledge is required. In this instance, the Court needed help understanding the differences between simplified and traditional Chinese characters, not political opinions or broader opinion evidence from linguistic experts.

Implications for Future Cases

This ruling serves as a reminder that experts should not express views on matters which fall outside their area of expertise or make legal or political comments. Judge Simons was particularly critical of one expert who expressed strong political views on the choice of script system. The judge held that this undermined his independence, resulting in the Court placing little weight on the expert evidence.

Conclusions and Practical Guidance

The judgment in this case underscores the importance of adherence to established principles governing expert evidence in Irish law. The judgment reiterates that when experts act as an advocate for their instructing parties or express politically charged opinions, it can severely undermine the weight and credibility of their testimony. Legal practitioners must ensure that they provide clear guidance to any experts they instruct, stressing the need for objectivity and the importance of remaining within their areas of expertise.

For more information on anything related to this article, please contact our Disputes and Litigation Team.

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

[2] Duffy v McGee [2022] IECA 254