Expert witnesses in UK courts - when you need one and how it works

If you are involved in a court case that hinges on technical or specialist knowledge - whether medical, engineering, financial, or scientific - an expert witness may be essential. Expert witnesses give evidence based on their qualifications and experience, not on what they personally saw or heard. They occupy a unique position: they work for the party that instructs them (usually your solicitor), but they owe their primary duty to the court, not to the side that pays them.

This guide explains what expert witnesses do in UK civil and criminal cases, what rules govern them under CPR Part 35, who pays, and how to find and instruct one.

The short version

An expert witness is a qualified professional (doctor, surveyor, accountant, engineer, etc.) who gives opinion evidence to help the court understand complex or technical matters. In civil cases, they are regulated by CPR Part 35. You typically need one when the case depends on specialist knowledge that neither party possesses. The court may order a single joint expert (appointed by agreement or by the judge), which is cheaper and faster than each side instructing its own. Expert fees can range from 2,000 to 10,000+ per case depending on discipline and complexity. Their duty to the court overrides loyalty to the party that hired them.

At a glance

What an expert witness is and is not

An expert witness is someone with professional qualifications, training, or substantial experience in a specific field who is instructed to give opinion evidence on matters within their expertise.

They are:

• Qualified by education, professional registration, or years of practice
• Instructed formally by a party's solicitor (or jointly by agreement)
• Bound by a duty to the court that supersedes loyalty to the instructing party
• Expected to remain impartial and declare any bias or interest
• Permitted to express opinions on matters outside the lay knowledge of the judge

They are not:

• Fact witnesses (who describe what they saw or heard)
• Advocates for the party that hired them
• Able to give evidence on matters of law or the ultimate issue (in some contexts)
• Able to withhold unfavourable evidence because they were instructed by one side
• Required to agree with the other side's expert

CPR Part 35 in plain English

CPR Part 35 sets out the rules for expert evidence in civil cases. It has 28 rules covering everything from instruction to the content of reports.

Key principles:

1. Expert evidence is exceptional. You need court permission to instruct an expert (unless the other side agrees). The judge will consider whether expert evidence is necessary, proportionate to the case value, and will genuinely help the court.

2. There is a single expert unless the court orders otherwise. CPR 35.7 requires the court to order a single joint expert (SJE) unless there is good reason. A single expert is cheaper and faster; both parties may put questions to them.

3. The expert has a duty to the court first. Rule 35.3(2) states that if there is any conflict between the expert's duty to the party that instructed them and their duty to the court, the duty to the court prevails. This is absolute.

4. Reports must be in a prescribed form. Rule 35.10 requires the expert to state that they understand the duty to the court and that they have complied with it. The report must set out the expert's qualifications, declare any conflicts of interest, and explain the substance of their instructions. Any material instruction to the expert (written) must be disclosed in the report.

5. Experts are expected to confer. If both parties instruct their own experts, rule 35.12 requires them to meet (usually in a conference) to identify areas of agreement, narrow issues, and explain disagreements. This is called an expert meeting or "hot-tub" (when conducted live in court).

6. The court can direct questions. Rule 35.6 allows the judge to put written questions to the expert at any stage. Both parties have the right to put supplemental questions.

7. Privilege does not apply. Unlike communications with your solicitor, correspondence between you and your expert witness (your instructions to them, their draft reports) can be disclosed to the other side. Only the work the expert did at the solicitor's direction, not the expert themselves, attracts legal advice privilege in some circumstances.

Single joint expert vs party-appointed expert

In civil cases, the court's presumption is towards a single joint expert (SJE).

Single joint expert (SJE):

• Instructed by both parties jointly (or appointed by the court)
• Costs are usually split equally
• Both parties can put questions to the expert
• Faster and more cost-effective
• More difficult to challenge (because the expert is neutral, not "yours")
• Used in most low-value and medium-value civil cases

Party-appointed expert:

• Instructed separately by one side
• Each side may instruct its own (though this requires court permission)
• The instructing party pays the expert's fees
• Both experts write reports; each is cross-examined
• More expensive and time-consuming
• Used when the single expert approach would be unjust or impractical (e.g. complex, high-value disputes; cases where expert opinion is highly contested)

The court will order a single joint expert unless you can show good reason - for example, that the issues are too complex, or that one party's expert would be compromised by a conflict of interest.

Common types of expert witness

The field of expert evidence is broad. Common types in civil cases include:

• Medical: orthopaedic surgeons, GPs, psychiatrists, nurses in clinical negligence cases
• Engineering: structural engineers, mechanical engineers, civil engineers in construction disputes
• Surveying: chartered surveyors in property damage, valuation, and defects claims
• Accountancy: chartered accountants in financial disputes, shareholder claims, business valuations
• Handwriting and signature: document examiners in forgery and authentication cases
• IT and computing: software engineers and data specialists in IP disputes and cybersecurity claims
• Valuation: jewellers, art experts, vintage specialists in insurance and estate disputes
• Pathology: forensic pathologists and toxicologists (mainly criminal cases)
• Psychology: clinical psychologists in family law and personal injury claims

Experts must be registered with a recognised professional body (such as the British Computer Society, the Royal Institution of Chartered Surveyors, or the General Medical Council) or demonstrate equivalent standing in their field.

How to find an expert witness in the UK

Via your solicitor: The most common route. Your solicitor will have networks of trusted experts and will instruct them on your behalf. They will brief the expert on the case, set deadlines, and manage the relationship.

Professional bodies and registers:

• The Expert Witness Institute (EWI) maintains a directory of vetted experts across many disciplines.
• The Law Society's Civil Practice Directory includes expert recommendations.
• Specialist bodies (RICS for surveyors, ICAEW for accountants, GMC for doctors) provide registers and can recommend appropriately qualified members.

Online directories: Websites such as Expert Witness Online, Expert Register, and the EWI's directory allow you to search by discipline, location, and experience.

Direct approach: If you know a professional in the relevant field (a friend's doctor, a colleague's accountant), you may ask whether they would be willing to act as an expert. However, they must be independent and have no conflict of interest.

Questions to ask:

• Are they registered with a recognised professional body?
• Have they given expert evidence before?
• Do they have any conflict of interest or connection to you, your opponent, or the case?
• Can they meet the court's deadlines?
• What is their fee structure (hourly rate, fixed fee, or daily rate)?

How much expert witnesses cost

Expert fees vary widely depending on discipline, experience, and case complexity.

Typical ranges:

• Medical experts: 150-400 per hour; full case fees from 2,500 to 10,000+
• Engineers and surveyors: 120-350 per hour; case fees from 2,000 to 8,000+
• Accountants: 150-400 per hour; case fees from 2,000 to 10,000+
• Handwriting and forensic experts: 100-250 per hour; case fees from 1,500 to 5,000
• IT and specialist fields: 150-500+ per hour; can exceed 15,000 on complex cases

What is usually charged:

• Initial consultation and case review
• Reading case papers and evidence
• Visiting the site or conducting examination (if applicable)
• Drafting the expert report
• Reviewing the other side's expert report
• Expert meeting or conference
• Court attendance and cross-examination
• Updating the report (if instructed)

Cost control: The court can cap expert fees or order costs to be shared if fees are considered excessive. Legal Aid may fund expert evidence in criminal cases and some civil cases (if you qualify). In civil cases, you can negotiate a fixed fee with the expert to control costs.

Duty to the court: the overriding principle

This is the golden rule of expert evidence. The expert's duty to the court overrides their obligation to the party that instructed them. This is not optional or flexible; it is a binding legal duty.

What this means in practice:

• The expert must give opinion evidence that is honest, fair, and based on the facts, even if it damages the case of the party that hired them.
• The expert must not mislead the court through omission or selective presentation of evidence.
• If the expert changes their mind or discovers new information, they must disclose it (via an updated report or supplemental statement).
• The expert must declare any bias, interest, or communication with the instructing party that might affect their impartiality.
• The expert must state the substance of their instructions in their report (so the court can see whether they have been asked to favour one side).
• An expert who breaches this duty may face disciplinary action, removal from professional registers, and potential liability for contempt of court.

Courts take this duty very seriously. If an expert is found to have been biased or to have withheld evidence, the entire report may be disregarded, and the expert may be reported to their professional body.

Day to day: what an expert's instruction looks like

Once you and your solicitor have decided to instruct an expert, here is the typical workflow:

1. Instruction letter: Your solicitor sends a formal letter to the expert setting out:

   • The nature of the dispute
   • The facts as your side sees them
   • What the expert is being asked to advise on
   • Any documents or evidence the expert will need to review
   • The deadline for the report
   • The expert's fee and how they will be paid

2. Scope of work: The expert confirms they understand the instructions, declare any conflicts of interest, and agree to the deadline and fee.

3. Review and examination: The expert reviews all documents, conducts any necessary examination (medical, structural, forensic, etc.), and gathers information.

4. Draft report: The expert prepares a full report setting out:

   • Their qualifications and experience
   • A statement confirming their duty to the court
   • The substance of their instructions
   • The facts and assumptions they are working from
   • Their findings
   • Their conclusions and reasons

5. Review by your solicitor: Your solicitor reviews the draft, may pose questions or ask for clarification, but should not ask the expert to change their opinion (if it is unfavourable, this is a matter for the expert to decide).

6. Other side's expert (if instructed separately): Both experts may exchange reports and hold a meeting (expert conference) to discuss their findings and narrow issues.

7. Questions: Both your solicitor and the opposing counsel may put written questions to the expert, which they must answer.

8. Court attendance: If the case goes to trial, the expert will give evidence, be examined by your counsel, and cross-examined by the opposing counsel.

9. Final statements: If the case settles before trial, the expert may not need to attend court, but may be paid for the work done up to that point.

Common misconceptions

"Expert witnesses are just advocates with a fancy title." Wrong. An expert's duty to the court is absolute. If their honest opinion favours the other side, they must say so. Judges are well attuned to biased experts and will disregard them.

"I can tell the expert witness what conclusion I want them to reach." Wrong. You can instruct an expert on the issues and the facts, but you cannot dictate their opinion. If you try, they must refuse or disclose the pressure in their report.

"Expert witnesses are only needed for complex technical cases." False. They are common in medical negligence, construction disputes, and professional indemnity claims of moderate complexity. The court will order expert evidence where it is proportionate and necessary.

"The single joint expert will always favour the other side." Not necessarily. A single joint expert is neutral. They are typically chosen for their impartiality, not their loyalty. Both parties can put questions to them.

"Once the expert report is filed, the expert's job is done." Not quite. The expert may be asked supplemental questions, must prepare for cross-examination if the case goes to trial, and may update their report if new evidence emerges.

"Expert witness evidence is always accepted by the judge." No. Judges assess expert evidence critically, weigh it against other evidence, and may reject or partially accept an expert's opinion if they find it unconvincing, biased, or based on flawed reasoning.

Related concepts

Privilege and disclosure: Unlike legal advice from your solicitor (which is privileged), communications with your expert witness are generally not privileged. Your instructions to the expert and draft reports may need to be disclosed to the other side. However, work the expert did purely at the direction of your solicitor (without being an expert in their own right) may attract legal advice privilege in some cases.

Expert meetings (the "hot-tub"): In civil cases, when both parties instruct their own experts, the rules encourage them to meet and confer (ideally before trial, but sometimes in court as part of the trial itself). This is sometimes called a "hot-tub" because both experts sit together. The aim is to narrow disagreements and help the judge.

Ultimate issue rule: In civil cases, experts may generally give opinion evidence on any matter within their expertise, including the ultimate issue (the core dispute). In criminal cases, the rules are more restrictive, and an expert may not give evidence on whether the defendant is guilty or on matters of law.

Cross-examination: Expert witnesses are cross-examined by the opposing counsel to test their evidence, explore bias, and challenge their reasoning. Unlike fact witnesses, experts are expected to hold their ground if they believe their opinion is sound.

Admissibility and reliability: The court will consider whether expert evidence meets the criteria for admissibility under the Civil Procedure Rules and common law. The evidence must be reliable, based on methodology accepted in the expert's field, and free from bias.

Costs and sanctions: If an expert acts unreasonably or in breach of the CPR, the court may sanction them by disallowing part of their fees, ordering them to pay costs, or referring them to their professional body.

Sources and further reading

• Civil Procedure Rules Part 35 - The statutory framework governing expert evidence in civil cases. www.justice.gov.uk/courts/procedure-rules/civil/rules/part35

• Expert Witness Institute (EWI) - Professional body for expert witnesses in the UK, providing guidance, training, and a directory of vetted experts. www.ewi.org.uk

• Law Society Civil Practice Directory - Guidance on instructing experts and a directory of specialist practitioners. www.lawsociety.org.uk

• Criminal Procedure Rules Part 19 - Rules governing expert evidence in criminal cases. www.justice.gov.uk/courts/procedure-rules/criminal/rules/part-19

• Guidance for Expert Witnesses (Civil and Criminal) - Published by the Expert Witness Institute and endorsed by the judiciary. Sets out best practice and ethical obligations.

Disclaimer

This page provides general information about expert witnesses in UK courts. It is not legal advice. The rules governing expert evidence are complex and vary depending on the type of case, the jurisdiction, and the circumstances. If you are involved in a court case and are considering instructing an expert witness, you should consult a qualified solicitor or barrister. The information on this page is current as of 28 May 2026 and is based on publicly available sources including the Civil Procedure Rules and official Court Service guidance. Laws and court procedures may change; always verify current rules with the Courts Service or your legal adviser.

Written by Peter Kolomiets, founder of CaseCalm. UK content reviewed 28 May 2026.