The 10 expert witness mistakes courts will no longer tolerate

Your reputation as an expert witness can be destroyed in a single court appearance. That is not an exaggeration. It is a direct warning from the Irish Court of Appeal.

In Duffy v McGee [2022] IECA 254, Mr Justice Collins described the culture of experts acting as advocates for the party who retained them as “unacceptable” and said it “needs to change.” The court did not simply reduce the weight given to the expert’s evidence. It excluded it entirely.

What has changed

The duties of an expert witness are long established. Order 39, Rule 57(1) of the Superior Courts Rules states that the expert’s duty is to assist the court, and that this overrides any obligation to the party paying the fee. The Ikarian Reefer principles, regularly cited in Irish courts, set out the requirements for independence, objectivity and impartiality.

What has changed is the consequence of getting it wrong. Courts are now excluding evidence outright rather than simply giving it less weight. Legal practitioners who instruct incompetent experts face potential wasted costs orders. The Law Reform Commission has recommended that expert witness duties be enshrined in legislation, with immunity from being sued abolished for cases of gross negligence.

For any professional who gives or may be asked to give evidence in Irish courts, the margin for error has narrowed considerably.

What the guide covers

La Touche Training has published a free practical guide identifying the 10 most common mistakes expert witnesses make in Irish courts.

Each mistake is explained with reference to real case law, its impact on evidence and credibility, and clear steps to avoid it.

Among the issues covered:

• The single most serious error that leads to evidence being ruled inadmissible, not just given less weight.
• Why straying outside your expertise can taint even the valid parts of your testimony.
• The “red flags” courts now actively look for in written reports.
• What the Supreme Court means when it warns against becoming “the thirteenth juror.”
• How personal attacks on opposing parties led to a complete exclusion of evidence in a recent Court of Appeal case.

The guide is relevant to medical professionals, engineers, accountants, forensic specialists, surveyors, psychologists, and any other professional whose technical expertise is relied on in legal proceedings. It is equally relevant to solicitors and barristers who instruct experts.

>> Download the free guide: The 10 most common expert witness mistakes in courts

La Touche Training’s Expert Witness Programme is Ireland’s leading training for professionals who give evidence in court, delivered by qualified barristers and solicitors with over 30 years of experience.

References: Duffy v McGee [2022] IECA 254 | Order 39, Rule 57(1), Rules of the Superior Courts | The Ikarian Reefer [1993] 2 Lloyd’s Rep. 68 | Law Reform Commission, LRC 117-2016.