Acting as a medical expert witness 

Ms Sile O’Dowd outlines the responsibilities and role for doctors called to be expert witnesses

Medical expert witnesses play a critical role in the justice system by bridging the divide between complex healthcare and the law.  Medical negligence claims in Ireland are judged against the ‘Dunne principles’, set out by the Supreme Court in the 1989 case of Dunne v National Maternity Hospital. In brief, a doctor is only negligent if it is proven that they made an error or omission that “no other reasonably competent practitioner” of equal status would have made while acting with ordinary care.

The relevant standard of care is established by reference to the medical profession’s own standards, not by judicial opinion. Trying to distinguish the clinical facts from issues of legal liability can be an extremely complex task. The expert witness plays a crucial role in helping the court understand what a reasonably competent practitioner would have done in similar circumstances. 

Factual vs expert witnesses

It is important to differentiate between acting as an expert witness and a factual witness.

Doctors frequently act as factual witnesses to give evidence concerning matters that they have personally witnessed, such as their examination of the patient and any treatment provided. The focus of their evidence is on firsthand facts and observations, as well as commenting on the patient’s prognosis based on these observed facts.

An expert witness is an independent individual with no link to a case, who is retained by either the plaintiff or the defendant to provide an expert opinion on matters outside the ordinary knowledge of the court. The primary role of the expert witness is to provide the court with objective, evidence-based opinions on clinical standards and causation, helping the court to arrive at its own independent opinion on the facts.

Duties of the expert witness

An expert’s paramount duty is to provide independent and truthful evidence to the court, regardless of the party retaining or paying them.

Order 39 Rule 57 of the Superior Court Rules (the ‘Rules’) provides:

57. (1) “It is the duty of an expert to assist the Court as to matters within his or her field of expertise. This duty overrides any obligation to any party paying the fee of the expert.”

The Rules require experts to acknowledge the above duty by including a declaration to that effect in any report prepared by them. A report that omits the declaration is procedurally defective. In addition, the Rules oblige all expert witnesses to disclose any financial or economic interest in any business or economic activity of the party retaining them.

Case law

The Irish courts have become increasingly firm with experts who stray into advocacy on behalf of the party retaining them.

The leading authority is the 2022 case of Duffy v McGee in which the Court of Appeal upheld the exclusion of a toxicologist expert for the defence whose evidence had strayed outside his discipline and relied on material that had not been peer reviewed.

The Court of Appeal took the view 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”.  The ruling emphasised the principle that an expert witness is there to assist the court in coming to its decision and in doing so, the expert may give their opinion solely on their area of expertise.

Before Duffy, the weight given to a partisan or overreaching expert report was a matter for consideration by the judge in deciding whether to discount the evidence or not. In the aftermath of Duffy, it is clear that a medical expert commenting on questions or on disciplines outside their expertise risks the whole report being excluded.

Ethical obligations

The ninth edition of the Medical Council’s Guide to Professional Conduct and Ethics for Registered Medical Practitioners (the ‘Guide’), published in 2024, mirrors the Rules. For the first time, it specifically addresses the duties of a doctor acting as an expert witness. The Guide provides as follows:

53.1 “If you are acting as an expert witness in relation to legal proceedings, your first duty is to be of assistance to the relevant court or tribunal in providing an independent expert opinion. You must be honest and objective in all your spoken and written statements.

53.2 You must make clear the limits of your knowledge and competence.

53.3 You must not act as an expert witness in areas outside your scope of practice, experience, and expertise.

53.4 These obligations override any instructions from the person paying you a professional fee for your expert opinion.”

It is important for practitioners to bear in mind that any breach of the provisions of the Guide could result in allegations of poor professional performance or professional misconduct.

Preparation and disclosure of reports 

One of the key roles of a medical expert witness is to prepare an expert report. There is no single statutory template strictly mandated for all medical expert reports. However, by way of general guidance, a well-structured expert report would be expected to include the following:

▶ Expert details: Name, current position, professional qualifications, and Medical Council of Ireland registration number.

▶ Instructions and chronology: A clear statement of the opinion requested, details of the requesting party, a list of all documents relied upon including medical records, test results, imaging and court pleadings, and a factual chronology of the relevant medical events and symptoms.

▶ Examination findings (if applicable): Date of examination, presentation history, clinical examination findings, and investigations.

▶ Opinion: An independent opinion on whether the care met the standard expected of a reasonably competent practitioner and/or addressing issues of causation if instructed to do so. The report should also include reference to any guidance literature relied on in reaching this opinion. 

▶ Declaration of any conflict of interest, financial interest, or economic interest.

▶ Declaration/Statement of truth: A state- ment affirming the expert’s overriding duty is to the court rather than the instructing party.

One important distinction between the approach to expert evidence in Ireland and the UK is that, in the UK, if an expert comments on a matter outside their expertise, their instructing solicitor can ask them to remove that comment from their report without impacting the expert’s duties to the court. There is no such equivalent provision in Ireland and it is important to bear in mind that any draft expert report provided by an expert to their instructing solicitor is disclosable to the other side. For that reason, it is important that experts are clear on what their instructions are and confine the report to matters within their expertise.

Clinical negligence practice directions

The clinical negligence practice directions were introduced on 28 April 2025. Since their introduction, clinical negligence cases are actively case-managed by the court, with clearer expectations regarding the timing of expert evidence, particularly related to quantum where there are now specific delivery timeframes (six weeks) where a report gives rise to further details of injuries or special damages.

While the directions are relatively new, the expectation is that under an active case management system, we are likely to see a move towards use of the expert conference mechanism (‘conclave’). This is where opposing party-appointed experts are directed to meet privately and produce a report, afterwards identifying the issues on which they agree and the ones that remain in dispute. These meetings take place in the absence of instructing solicitors. The reason for them is so that the judge and parties can see exactly what is contested before any oral evidence is heard.

The directions are also expected to give rise to opposing experts more frequently being directed to give their evidence together, sometimes called concurrent evidence or, colloquially, ‘hot-tubbing’. This entails each expert being sworn and the judge chairing a structured discussion of the points left unagreed in any joint expert report.

Conclusion

Acting as a medical expert witness is a significant professional responsibility, not simply an extension of clinical practice. The expert’s role is to assist the court with clear, independent, and objective opinion evidence, confined to their own area of expertise and supported by the material available to them. Recent case law, the Medical Council’s Guide and the clinical negligence practice directions all reinforce the same message: Experts must understand the limits of their role, be transparent about conflicts and interests, and avoid advocacy.

Acting as a medical expert witness is a significant professional responsibility, not simply an extension of clinical practice

References available on request