The Role and Duties of Expert Witnesses in the UK Legal System

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 content.

A Landmark Case: Jones v Kaney

The seriousness of expert witness duties is highlighted by the landmark case of Jones v Kaney [2011] UKSC 13. 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. This ruling emphasised the importance of expert witnesses adhering to the highest standards of professionalism and impartiality. To learn more click here for a case summary of Jones v Kaney.

Professional Witness v Expert Witness

In general

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.“

Blurred boundaries

While both types of witnesses have a duty to be truthful and objective, the role of the expert witness carries a greater emphasis on impartiality and independence, as they are expected to provide opinions that are unbiased and uninfluenced by the parties involved. It depends on to whom professional witness statements are given. If to an insurance company or some other private organisation, there would be obvious duties to be robust and honest. What if a professional witness is reporting to a Tribunal in writing – and then giving oral evidence? That situation is covered in more detail below. It is quite probable that evidence to a Tribunal will be expected to step over any notional boundary from professional into expert witness role and standards.

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. For example, a treating doctor who initially provides factual evidence about a patient’s injuries may be asked to give an expert opinion on the likely cause of those injuries or the long-term prognosis. In such cases, they would be expected to adhere to the same duties of impartiality and independence as any other expert witness. Beware of GMC standards.

Expert Evidence to Tribunals

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.

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.

The author had direct experience of sitting in Criminal Injuries Compensation Appeals Tribunals (CICAT). In that scenario the author as a judicial officer member, was often engaged in drafting instructions to expert witnesses e.g. psychiatrists, psychologists, neuro-occupational therapists etc. The expectations of diligence, impartiality and independence were ever present.

Sources of Duties and Standards for Expert Witnesses

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

Source	Key Provisions	Relevant Rule/Case Law
Common Law	Establishes fundamental principles of expert witness conduct, particularly in civil cases.	Ikarian Reefer 1
Civil Procedure Rules (CPR)	Outlines responsibilities of experts in civil proceedings, including the overriding duty to the court.	Part 35 of the CPR
Criminal Procedure Rules (CrimPR)	Provides guidance on expert evidence in criminal cases, emphasising objectivity and expertise.	Part 19 of the CrimPR
Professional Codes of Conduct	Offer further guidance for expert witnesses in specific fields, often emphasising professional integrity and ethical conduct.	Expert Witness Institute (EWI), Law Society of Scotland, the General Medical Council .

Overriding Duty to the Court

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 enshrined in both the CPR(Part 35) and CrimPR. Part 19.2 of the CrimPR explicitly states that an expert has an overriding duty to give objective and unbiased opinion evidence. This duty extends to defining their area of expertise when presenting evidence.

Experts my may meet with persons who are subject to court matters. This is usually contracted by a lawyer. It is not be unusual to hear an appellant say, “I know you’re here to get me off..” or “I hope you can convince the court to give me a lighter sentence...” or “Please prove me insane.” Experts would be well advised to manage such situations tactfully and not give or imply agreement to such statements.

Key Duties and Standards

Mentioned previous were the CPR and the CrimPR. See a comparison below

You’re right, creating a table to summarise the similarities and differences would be helpful! Here’s a table outlining the key aspects of expert witness duties under the CPR and CrimPR:

Feature	Civil Procedure Rules (CPR)	Criminal Procedure Rules (CrimPR)
Overriding Duty to the Court	Yes, CPR 35.3	Yes, CrimPR 19.2
Independence	Yes	Yes
Impartiality	Yes	Yes
Confining Opinions to Expertise	Yes	Yes
Transparency	Yes	Yes
Compliance with Court Directions	Yes	Yes
Disclosure of Information	Focus on completeness of report for court’s understanding	Emphasis on early and comprehensive disclosure, including potentially unfavorable information
Single Joint Expert	Actively encouraged	Less common, often depends on the case and parties’ agreement
Discussions between Experts	Structured framework for discussions to identify and resolve disagreements	Less structured, may occur on an ad hoc basis
Immunity from Suit	No immunity since Jones v Kaney [2011] UKSC 13	No immunity

This table provides a concise overview of the key similarities and differences between the CPR and CrimPR in relation to expert witness duties. It highlights the core principles that apply across both sets of rules, as well as the specific nuances that experts need to be aware of in each context.

Independence and Impartiality

Expert witnesses must provide independent and unbiased opinions based on their expertise. They should not act as advocates for any party involved in the case. This requires them to:

• Remain objective and avoid being influenced by the pressures of litigation. For example, an expert witness should not let the desire to please their instructing party influence their opinion or the way they present their evidence.
• Consider all material facts, including those that may detract from their opinions. If an expert discovers information that weakens their initial opinion, they must disclose it to the court and revise their opinion accordingly.
• Clearly state the facts or assumptions upon which their opinions are based. This allows the court to understand the reasoning behind the expert’s conclusions and assess the weight to be given to their evidence.
• Disclose any potential conflicts of interest. For instance, if an expert has a personal or financial relationship with one of the parties, they must disclose this to the court.

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. They should consult authoritative sources and use appropriate methodologies.
• 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. ¹¹ Many professions have codes of conduct that provide specific guidance for expert witnesses, such as maintaining confidentiality and avoiding conflicts of interest.

Clarity and 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. For example, instead of using technical jargon, an expert witness might explain a complex medical condition in simple terms that a jury can easily understand.
• Defining their area of expertise and making it clear when a question falls outside their scope. If a lawyer asks an expert witness a question about a topic outside their expertise, they should state that they are not qualified to answer.
• Identifying any limitations in their research or data. If an expert’s opinion is based on limited data or research, they should acknowledge this and explain how it might affect the reliability of their conclusions.
• Explaining any changes in their opinions promptly. If an expert receives new information or changes their opinion after reviewing further evidence, they must inform the court and the parties involved as soon as possible.

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, R v. Burridge.

The General Medical Council’s standards Providing witness statements or expert evidence as part of legal proceedings content, does 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.

The Ikarian Reefer Case

The Ikarian Reefer case is a landmark judgment that has significantly shaped the understanding of expert witness duties in civil cases. The case highlighted the importance of independence, objectivity, and transparency in expert evidence. It emphasised that experts should not act as advocates and must consider all material facts, even those that may weaken their conclusions. 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.

The standards expected by the court, as established in the Ikarian Reefer case, are still applicable today and include:

1. Independence: Expert evidence should be the independent product of the expert, uninfluenced by the pressures of litigation
2. Impartiality: An expert witness should provide independent assistance to the court by way of objective, unbiased opinion in relation to matters within their expertise.
3. Duty to the Court: An expert witness in the High Court should never assume the role of an advocate
4. Transparency: An expert witness that could detract from their concluded opinion.
5. Scope of Expertise: An expert witness should make it clear when a particular question or issue falls outside their expertise.
6. Provisional Opinions: If an expert’s opinion is not properly researched because they consider that insufficient data is available, then this must be stated with an indication that the opinion is no more than a provisional one ³.

Standards from Recent Case Law

While the Ikarian Reefer case remains a cornerstone of expert witness duties, recent case law has further clarified and refined these standards. Here are some notable examples from the last 10 years:

• R (Suez Recycling and Recovery UK Ltd) v Environment Agency [2023] EWHC 3012 (Admin): This case clarified that claimants can submit witness statements from other organisations without those organisations needing to formally intervene in the case [39]. This can be particularly relevant when seeking to present evidence on wider systemic issues.
• 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. This underscores the weight given to expert testimony and the importance of proper scrutiny.
• R (Elliott Associates LP) v The London Metal Exchange [2022] EWHC 282 (Comm): This case highlighted the importance of supporting witness evidence with contemporaneous documents. If such documents are lacking, the court may give less weight to the evidence, especially if it involves recalling past events.
• Worboys Case [2018] EWHC 935 (Admin): This high-profile case involving a convicted sex offender demonstrated the critical role of expert witnesses in parole board decisions. It also highlighted the potential for public and legal scrutiny of expert opinions, particularly in sensitive cases.

These cases demonstrate the ongoing evolution of expert witness standards and the importance of staying abreast of recent developments in case law.

Actions Against Expert Witnesses

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

Legal Actions

• Challenges to evidence: Opposing parties can challenge the admissibility or weight of expert evidence if the expert has not complied with their duties. For example, in TUI UK Ltd v Griffiths [2021] UKSC 47, the Supreme Court emphasised the importance of challenging expert evidence through cross-examination or contrary evidence, highlighting that simply dismissing expert evidence without proper scrutiny can be unfair.
• Claims for negligence: In some cases, parties may be able to bring claims for negligence against expert witnesses who have provided negligent or inaccurate opinions. This could arise if the expert has failed to exercise reasonable skill and care in their work, leading to a loss for the instructing party.
• Contempt of court: In extreme cases, expert witnesses who deliberately mislead the court or wilfully disregard court orders could be found in contempt of court. This can result in fines or even imprisonment.

Regulatory Actions

• Professional disciplinary proceedings: Many professions have regulatory bodies that oversee the conduct of their members, including those who act as expert witnesses. For example, the General Medical Council (GMC) regulates doctors, and the Law Society regulates solicitors. These bodies can investigate complaints against expert witnesses and take disciplinary action, such as issuing warnings, imposing fines, or even striking off members from their registers.
• Reputational damage: Even if no formal legal or regulatory action is taken, an expert witness who fails to uphold their duties can suffer significant reputational damage. This can affect their credibility and future prospects as an expert witness.

Examples of Actions Taken

• In the Worboys Case [2018] EWHC 935 (Admin), the parole board’s decision to release a convicted sex offender based on expert evidence was challenged and overturned by the High Court. This case highlighted the potential for scrutiny of expert opinions and the consequences of failing to meet the required standards.
• The Crown Prosecution Service (CPS) guidance for expert witnesses states that failure to disclose relevant information can lead to prosecution delays, overturned convictions, and undermine the expert’s credibility. It can also result in action by the expert’s professional body or the accused against them.

It is important for expert witnesses to understand the potential consequences of failing to comply with their duties and to maintain the highest standards of professional conduct throughout their involvement in a case.

Compliance with Court Directions

Expert witnesses must comply with court directions and orders.

• Provide reports and attend court hearings as required. Experts must submit their reports within the deadlines set by the court and attend hearings to give oral evidence when requested.
• Actively assisting the court in managing the case efficiently and proportionately. This includes complying with court directions, informing the court of any delays or difficulties, and generally working to ensure the case progresses smoothly.
• Hot-tubbing: Subject to specific directions of the court, experts may discuss and potentially resolve differences in their opinions. This can help narrow the issues in dispute and potentially lead to a settlement. Other than the latter framework, experts are not allowed to discuss cases in their consideration with anyone else. One would not expect a judge to discuss a case with some friend over a pint in a pub. [This does not mean that expert witnesses are judges].

Professional Codes of Conduct

Professional organisations, such as the EWI and the Law Society of Scotland, provide codes of conduct that offer further guidance for expert witnesses. These codes often emphasise the importance of:

• Maintaining professional integrity and upholding the reputation of the profession. This includes acting honestly and ethically in all dealings with the court, instructing parties, and other experts.
• Avoiding conflicts of interest. Experts should decline instructions if they have any personal or financial interests that could compromise their impartiality.
• Communicating effectively with instructing parties and the court. This involves providing clear and concise reports, responding promptly to requests for information, and being prepared to explain their opinions in court.
• Keeping up-to-date with developments in their field of expertise. Experts have a duty to maintain their competence and keep abreast of new research and developments in their field.

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. Their commitment to independence, impartiality, and clear communication is vital for maintaining the integrity of the legal process and assisting the court in reaching informed and just decisions.

The role of the expert witness is a privileged one. 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 applicabel to medical-doctor expert and professional witnesses.

Reading list

1. British Veterinary Association, Giving Evidence in Court: A Guide for Veterinary Surgeons (2023) https://www.bva.co.uk/resources-support/ethical-guidance/giving-evidence-in-court-guide/.
2. Acting as an expert or professional witness – Guidance for healthcare professionals AOMRC (2019)
3. The Medical Defence Union, Your Questions Answered (2022) https://www.themdu.com/guidance-and-advice/guides/your-questions-answered.
4. Four famous expert witness cases: https://www.expertcourtreports.co.uk/blog/four-famous-expert-witness-cases/
5. HM Courts & Tribunals Service, Tribunals (2024) https://data.justice.gov.uk/courts/tribunals.
6. General Medical Council, Providing Witness Statements or Expert Evidence as Part of Legal Proceedings (2023) https://www.gmc-uk.org/professional-standards/the-professional-standards/providing-witness-statements-or-expert-evidence-as-part-of-legal-proceedings/providing-witness-statements-or-expert-evidence-as-part-of-legal-proceedings.
7. Doctors’ Defence Service, Doctors Who Act as Expert Witnesses May Be Subject to GMC/MPTS Misconduct Proceedings https://doctorsdefenceservice.com/doctors-who-act-as-expert-witnesses-may-be-subject-to-gmc-mpts-misconduct-proceedings/.
8. Expert Witness Institute, Code of Practice https://www.ewi.org.uk/About/Code-of-Practice.
9. Law Society of Scotland, Expert Witness Code of Practice https://www.lawscot.org.uk/members/business-support/expert-witness/expert-witness-code-of-practice/.
10. Criminal Procedure Rules 2020 (CrimPR).
11. Health and Safety Executive, The Expert Witness’s Role https://www.hse.gov.uk/enforce/enforcementguide/investigation/expert-role.htm.
12. College of Optometrists, Guidance Booklet for Expert Witnesses (2015) https://www.college-optometrists.org/coo/media/media/documents/expert%20witness/guidance-booklet-for-expert-witnesses-june-15-pdf.pdf.
13. Judiciary, Guidance for the Instruction of Experts in Civil Claims (2014) https://www.judiciary.uk/wp-content/uploads/2014/08/experts-guidance-cjc-aug-2014-amended-dec-8.pdf.
14. Expert Evidence International, The 13 Duties of Expert Witnesses in Common Law Courts https://expertevidence.ie/the-13-duties-of-expert-witnesses-in-common-law-courts/.
15. Crown Office Chambers, Jones v Kaney (2017) https://www.crownofficechambers.com/wp-content/uploads/2017/01/jones_v_kaney_article.pdf.
16. Crown Prosecution Service, Expert Witness Guide https://www.copfs.gov.uk/for-professionals/expert-witness-guide/.
17. The Ikarian Reefer https://www.ewi.org.uk/Knowledge-Hub/Rules-and-Regulations/Ikarian-Reefer
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19. Stewarts Law, What Qualities Does an Expert Witness Require and What are Their Duties? https://www.stewartslaw.com/news/what-qualities-does-an-expert-witness-require-and-what-are-their-duties/.
20. Civil Procedure Rules 1998 (CPR), Practice Direction 35 – Experts and Assessors.
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22. Pinsent Masons, UK Supreme Court: Fair Treatment of Expert Evidence at Trial https://www.pinsentmasons.com/out-law/news/uk-supreme-court-fair-treatment-expert-evidence-trial.
23. Expert Court Reports, Four Famous Expert Witness Cases https://www.expertcourtreports.co.uk/blog/four-famous-expert-witness-cases/.
24. Crown Prosecution Service, Expert Evidence https://www.cps.gov.uk/legal-guidance/expert-evidence.
25. Office for Nuclear Regulation, Enforcement Guidance 010: Expert Witness (2023) https://www.onr.org.uk/media/z3njhe0i/onr-enf-gd-010.docx.