Estimated reading time at 200 wpm: 15 minutes

Part 1: Defining the Role in Legal Proceedings

Introduction

The role of the expert witness is frequently misunderstood. Contrary to certain portrayals in American media, which often depict expert witnesses as partisan advocates, expert witnesses within the UK legal system bear an overriding duty to the court itself. This fundamental distinction is crucial for a comprehensive understanding of the function and obligations of expert witnesses within the UK legal framework. Expert witnesses are individuals possessing specialised knowledge and expertise within a specific domain. Their engagement in legal proceedings confers upon them distinct privileges and responsibilities, most notably the provision of objective and impartial opinions to aid the court in reaching well-informed decisions.

The author found that all the relevant standards and duties were not in one place. This article aims to pull all roles and duties together and explain their seriousness within the UK legal system. Training matters are not covered in this article – except to say that expert witnesses ought to ensure they are properly trained before taking on expert witness work. Psychiatrists would do well to heed General Medical Council’s standards: Providing witness statements or expert evidence as part of legal proceedings (Dec 2024).

For history go: A Brief History of the Expert Witness – PMC

Expert Witness vs. Professional Witness

It is important to distinguish between a “professional witness” and an “expert witness“, while acknowledging that the roles can sometimes overlap.

A professional witness is someone with professional qualifications and direct involvement in the facts of the case, such as a treating doctor. They provide factual evidence based on their personal knowledge and observations. On Professional Witness to fact or corroboration, the AOMRC (2019) states, “In these cases, the healthcare professional will generally have been directly involved in the management of the patient in the case being considered. The witness is expected to provide professional evidence of their clinical findings, observations and actions. Witnesses of fact must limit their evidence as far as possible to what is recorded or remembered and should not venture to give opinion or speculate on events. Being a witness of fact will generally be a requirement rather than a matter of choice.“

An expert witness, on the other hand, provides an opinion to the court based on their expertise in a particular field. They may or may not have been directly involved in the events of the case, but they use their specialised knowledge to interpret the evidence and assist the court in understanding complex issues. On expert witness, the AOMRC (2019) states, “The role of an expert witness is to assist the court on matters which are outside the knowledge and experience of the court and which, by virtue of their knowledge, training, or experience, are within the healthcare professional’s field of expertise. The expert witness will not, other than in highly exceptional circumstances, have been personally involved with the patient in the case and must declare any potential conflicts of interest. They are providing evidence (written or oral) because of their specialised knowledge of a specific field relevant to the case. It is a matter of choice for a healthcare professional as to whether to act as an expert witness (although occasionally it may be a requirement). Normally, the expert will be asked by solicitors or other parties if they are willing to accept instruction to assist in the case by providing an expert report.“

The Blurred Boundary in Practice: Mental Health Tribunals (MHTs)

Mental Health Tribunals (MHTs) are judicial decision-making bodies that operate within a legal framework. They make decisions that affect Human Rights. While not technically classified as “courts” in the traditional sense, they function similarly to courts and are subject to legal principles and procedures. In European law – applicable in the UK – MHTs are considered to be courts.

In the context of MHTs, the distinction between “professional witness” and “expert witness” can become blurred. A consultant forensic psychiatrist, for example, may initially provide a report based on their observations and factual knowledge of a patient, acting as a professional witness. However, when giving oral evidence and offering professional opinions on matters such as the patient’s mental state, risk assessment, or treatment needs, their role shifts towards that of an expert witness. It is important to bear in mind that a professional witness can become an expert witness if/when they are asked to provide opinions based on their expertise during legal proceedings.

Despite this potential ambiguity or grey area, MHTs expect the same high standards of impartiality and balance. This means that even when presenting factual information, witnesses must strive to be objective and avoid advocating for a particular outcome. However, it is appropriate for a psychiatrist at a Tribunal to give reasoned, evidence-based opinion on whether a detained patient is ready for discharge from detention – if asked to express an opinion.

Essentially, while the labels of “professional witness” and “expert witness” may not always be neatly applied in the context of MHTs, the underlying principles of impartiality, objectivity, and a commitment to assisting the Tribunal in reaching a just decision remain paramount.

Other potentially blurred boundaries

Some doctors (not me) of the stupid variety, accept private contracts from relatives of patients (or patients themselves) for expert second opinion. There is a real possibility that such opinions may come into view of the courts and dissected as if they are ‘expert witness reports’. Because the authors of such a report is obviously willing to risk their reputation. No sort of report should be the ‘hired gun’ type.

Part 2: The Core Duties and Standards of an Expert Witness

Your Overriding Duty to the Court and the Pillars of Conduct

A core principle for expert witnesses is their overriding duty to the court. This means their primary responsibility is to assist the court in reaching a just and fair outcome, regardless of who instructs them or pays their fees. This duty is explicitly stated in both the Civil Procedure Rules (CPR) and the Criminal Procedure Rules (CrPR):

• CPR 35.3 states: “(1) It is the duty of experts to help the court on matters within their expertise. (2) This duty overrides any obligation to the person from whom experts have received instructions or by whom they are paid.”
• CrPR 19.2 mirrors this, stating the expert’s duty is to give “objective, unbiased opinion on matters within [their] expertise.” It explicitly adds that this “overrides any obligation to the person from whom the expert receives instructions or by whom the expert is paid.”

The expert is therefore not a “hired gun” or an additional advocate for a client. They are an impartial resource for the judge and jury. To put it bluntly, “The Court owns you, not the lawyer who instructed you.”

The practical application of this overriding duty rests on three intertwined concepts: Independence, Impartiality, and Objectivity.

1. Independence: This means the expert must be free from any connection to or pressure from the instructing parties that could influence their evidence. This includes both financial independence (an expert’s fee should not be conditional on the outcome) and intellectual independence (the expert must form their own genuine opinion and resist pressure to change it).
2. Impartiality: This relates to the expert’s state of mind. They must be unbiased, even-handed, and must not favour one side over the other. The appearance of impartiality is just as important as the reality.
3. Objectivity: This refers to the expert’s methodology. Their conclusions must be based on the facts of the case, supported by evidence, and derived from a process of sound reasoning within their field of expertise.

Avoidance of Public Comment: A Cardinal Rule

Expert Witness training at Bond Solon emphasised ‘never comment on any live case you are currently engaged in, in public.’ That’s not a quotation of Bond Solon but it was the emphasis and similar words were used. That was/is a critical firewall that protects these principles. Engaging in public discussion, especially on social media, damages an expert’s standing in relation to the court, for several reasons:

• Damages impartiality: It gives the unavoidable impression that the expert has become a partisan advocate, taking a public side in the proceedings.
• Invites contempt of Court: It creates a substantial risk of seriously prejudicing the course of justice, a criminal offence under the Contempt of Court Act 1981.
• Damages credibility: In court, any public comments would be used by opposing counsel during cross-examination to destroy the expert’s credibility. They would be portrayed as a biased commentator, not an impartial expert, and their evidence would be rendered worthless.
• Violates duty to the Court: By taking the matter into the court of public opinion, the expert is fundamentally disrespecting the authority and process of the actual court they are supposed to be assisting.

It does not matter what an individual expert or group of experts think i.e. Whether they breach any of the above by making some careful comment on social media. What matters is what the court would think. Those wishing to second guess what the Court might think are free to take their chances.

The Duty of Reasonable Skill and Care

Expert witnesses are expected to exercise reasonable skill and care in their work, adhering to the standards of their profession. This includes:

• Conducting thorough research and analysis. Experts must ensure their opinions are based on a sound understanding of the relevant facts and research.
• Applying their expertise with due diligence. This involves carefully considering all relevant factors and applying their knowledge and skills to reach well-founded conclusions.
• Ensuring the accuracy and reliability of their opinions. Experts should take steps to verify their findings and ensure their opinions are supported by the available evidence.
• Complying with relevant professional codes of ethics.

The Duty of Clear Communication

Expert witnesses should communicate their findings and opinions clearly and concisely, both in written reports and when giving evidence in court. This involves:

• Using plain language that is understandable to the court and lay people.
• Defining their area of expertise and making it clear when a question falls outside their scope.
• Identifying any limitations in their research or data.
• Explaining any changes in their opinions promptly.

Part 3: The Legal and Professional Framework

Sources of Your Duties (The Rulebook)

The duties and standards expected of expert witnesses in the UK originate from several sources:

Landmark Cases That Define Practice

• The Ikarian Reefer Case: This is a landmark judgment that has significantly shaped the understanding of expert witness duties in civil cases. It established that expert evidence should be the independent product of the expert, uninfluenced by litigation pressures; that the expert must provide objective, unbiased assistance to the court; that they must state the facts their opinion is based on; and must make it clear when an issue falls outside their expertise. Crucially, the case established that if an expert’s opinion is based on insufficient data, this must be stated, and the opinion should be presented as provisional.
• Jones v Kaney [2011] UKSC 13: The seriousness of expert witness duties is highlighted by this landmark case. The UK Supreme Court reversed a legal immunity afforded to expert witnesses that had stood for 400 years. The UKSC stripped that immunity so that henceforth expert witnesses were no longer immune from suit for negligence in civil claims. This means that experts can be held accountable for providing negligent or inaccurate opinions, just like any other professional.
• R v. Burridge: This case is relevant to professional conduct. Expert witnesses are expected to maintain high standards of professional conduct throughout their involvement in a case. This includes respecting other witnesses in the case and refraining from making personal attacks or unfounded accusations.
• Recent Developments: Recent case law has further clarified and refined these standards. In TUI UK Ltd v Griffiths [2021] UKSC 47, the Supreme Court held that a trial judge cannot generally dismiss expert evidence without cross-examination or contrary expert evidence, underscoring the weight given to expert evidence.

The General Medical Council (GMC): Your Professional Regulator

Most doctors fear the GMC even if they deny that. Key Principles from Providing witness statements or expert evidence as part of legal proceedings – GMC came into effect late in December 2024, making the professional obligations crystal clear. It is not advisory; it is the standard against which a doctor’s conduct will be judged.

The duties re-emphasised and clarified in this guidance include:

1. The Primacy of Duty to the Court.
2. Honesty, Accuracy, and Trustworthiness.
3. Objectivity and Impartiality.
4. Clarity on Limits of Expertise.
5. The Formal Declaration: The guidance underpins the importance of the Statement of Truth. In signing this, the doctor formally declares they have understood and complied with their duty to the court.

The GMC’s standards do not occupy itself with distinctions between professional and expert witnesses. Instead, it sets out standards for being part of legal proceedings. This means that the standards apply to psychiatrists who write reports to MHTs or give live oral evidence to MHTS. A breach of the standards is good grounds from being struck off or suspended from medical practice.

Part 4: Practical Application and Consequences

Compliance with Court Directions

Expert witnesses must comply with court directions and orders. This includes providing reports and attending court hearings as required, and actively assisting the court in managing the case efficiently and proportionately. Subject to specific directions of the court, experts may discuss and potentially resolve differences in their opinions in a process sometimes called “hot-tubbing.” Other than this formal framework, experts are not allowed to discuss cases in their consideration with anyone else.

When Things Go Wrong: Actions Against Expert Witnesses

When expert witnesses fail to adhere to their duties and standards, various actions can be taken against them, ranging from legal repercussions to professional disciplinary measures.

• Legal Actions: These include challenges to the admissibility or weight of evidence; claims for negligence following the removal of immunity in Jones v Kaney; and, in extreme cases of deliberately misleading the court, a finding of contempt of court, which can result in fines or imprisonment.
• Regulatory Actions: Regulatory bodies like the GMC can investigate complaints and take disciplinary action, such as issuing warnings, imposing fines, or even striking off members from their registers. An expert witness who fails to uphold their duties can also suffer significant reputational damage that can affect their credibility and future prospects.

Conclusion

This article has provided a comprehensive overview of the duties and standards expected of expert witnesses in the UK legal system. By adhering to these principles, derived from common law, the Civil Procedure Rules, the Criminal Procedure Rules, and professional codes of conduct, expert witnesses play a vital role in ensuring the fair administration of justice.

The role of the expert witness is a privileged one. Expert witnesses have certain privileges that ordinary witnesses of fact do not, such as being able to express opinions and hear other evidence. However, these privileges are managed by a range of case law, regulations and other expectations from case law precedent. As expert witnesses serve the courts, they are individually responsible to ensure the correct standards are applied. The GMC has unified standards applicable to medical-doctor expert witnesses and professional witnesses, making clear the seriousness of these duties.