An expert witness is a person with specialist knowledge, skill or experience who gives a court an independent opinion on a question the judge cannot answer unaided. In civil claims in England and Wales the rules are in Part 35 of the Civil Procedure Rules. An expert is "a person who has been instructed to give or prepare expert evidence for the purpose of proceedings" (CPR 35.2), and their duty to help the court overrides any obligation to whoever instructs or pays them (CPR 35.3). In clinical negligence and personal injury claims most expert witnesses are doctors, nurses and other clinicians, and this guide is written with the medical expert in mind.

The practical bottom line

  • What they do. Give an opinion, in a written report and sometimes in the witness box, on matters within their expertise that the court needs help with.
  • Who they answer to. The court. The duty in CPR 35.3 overrides any obligation to the party paying the fee.
  • Who qualifies. Anyone with the knowledge and experience the issue needs, who is impartial and draws on a reliable body of knowledge. There is no licence or compulsory accreditation, apart from MedCo for first reports in whiplash claims.
  • How they are used. No party may call an expert or put in an expert's report without the court's permission (CPR 35.4).
  • How they are paid. By the instructing party, or jointly for a single joint expert, on terms agreed at the outset. Fees that depend on the outcome are strongly discouraged.

What is an expert witness?

Most witnesses can only tell the court what they saw, heard or did. The law lets an expert go further and give an opinion, because some questions cannot be answered without specialist knowledge: whether a fracture was missed on an X-ray, whether a delay in surgery changed the outcome, how long a claimant's symptoms are likely to last. The expert's job is to help the judge decide those questions. The decision itself stays with the judge, who can prefer one expert to another or reject expert evidence that does not hold together.

A treating doctor is usually a witness of fact. A GP who saw the claimant the day after an accident can describe what they found and what they recorded, and opinion evidence normally comes from an independent expert with no part in the patient's care. The GMC's guidance on providing witness statements or expert evidence sets out separate responsibilities for each role.

Criminal and family cases have their own rules, in Part 19 of the Criminal Procedure Rules and Part 25 of the Family Procedure Rules, and Scotland has its own procedure. The core duty of independence is the same in all of them.

What does an expert witness do in a civil claim?

In a clinical negligence or personal injury claim the work usually runs in this order:

  • Accept the instruction. Confirm the issue is within your expertise, check for conflicts of interest, and agree terms of appointment covering fees, the delivery date and court attendance.
  • Review the evidence. Read the medical records, imaging, witness statements and anything else the instructions supply, and examine the claimant where the issue calls for it.
  • Write the report. Practice Direction 35 sets out what it must contain, ending with a statement of truth and a statement that the expert understands and has complied with their duty to the court. Our guide to writing an expert witness report covers the structure.
  • Answer written questions. A party may put written questions about the report within 28 days of service, for the purpose of clarification, and the answers become part of the report (CPR 35.6).
  • Meet the other expert. The court can direct the experts to discuss the issues and prepare a statement of what they agree and disagree on, with reasons (CPR 35.12). Our joint statement checklist covers how to prepare.
  • Give evidence at trial. Only if the case gets that far and the court needs oral evidence. Most claims settle first, and on the small claims and fast tracks the court will not direct an expert to attend a hearing unless it is necessary in the interests of justice (CPR 35.5).

In clinical negligence the issues usually divide between experts: breach of duty, judged by the Bolam test; causation; and condition and prognosis, which feeds into the value of the claim. Each produces its own kind of medico-legal report.

What is an expert witness's duty to the court?

CPR 35.3 puts it in two sentences: experts must help the court on matters within their expertise, and that duty overrides any obligation to the person who instructs or pays them. Practice Direction 35 sets out what that means in practice:

  • the evidence should be the independent product of the expert, uninfluenced by the pressures of litigation (para 2.1);
  • opinions should be objective and unbiased, and the expert should not take on the role of an advocate (para 2.2);
  • the expert should consider all material facts, including those that might detract from their opinion (para 2.3);
  • the expert should say when a question falls outside their expertise, or when they cannot reach a definite opinion (para 2.4);
  • a change of view on a material matter should be communicated to all parties without delay (para 2.5).

These principles go back to Cresswell J's summary of the expert's duties in The Ikarian Reefer [1993] 2 Lloyd's Rep 68. The Civil Justice Council's guidance for the instruction of experts adds a practical test of independence: the expert would express the same opinion if given the same instructions by another party. For the duty in more depth, see our refresher on Part 35 and the expert's duty to the court, and for every rule in Part 35, our guide to CPR 35.

Who can be an expert witness?

No qualification, licence or register makes someone an expert witness. The court decides, case by case, whether evidence is admissible as expert evidence. In Kennedy v Cordia (Services) LLP [2016] UKSC 6, a Scottish appeal, the UK Supreme Court identified four considerations that govern whether skilled evidence is admissible:

  1. whether the evidence will assist the court in its task;
  2. whether the witness has the necessary knowledge and experience;
  3. whether the witness is impartial in presenting and assessing the evidence;
  4. whether there is a reliable body of knowledge or experience behind the evidence.

For a medical expert, the second question usually decides it. The expert should practise in the specialty the issue concerns, at the level in question: a GP's care is assessed by a GP, a consultant obstetrician's by a consultant obstetrician. Current or recent clinical practice matters too, and an expert who stopped practising long before the events in issue can expect the point to be raised in cross-examination.

Permission is tied to the expert. When the court gives permission it covers only the expert named or the field identified in the application (CPR 35.4(3)), and on the small claims and fast tracks it is normally given for one expert per issue (CPR 35.4(3A)).

How is an expert witness instructed?

  • Party-appointed expert. Each side instructs its own expert. Permission is not needed to instruct an expert, but it is needed to rely on the report or call the expert at trial, and the party applying must give an estimate of the costs and identify the field and the issues the evidence will address (CPR 35.4(2)).
  • Single joint expert. The court can direct that one expert reports on an issue for all the parties (CPR 35.7). Any party may give instructions, copied at the same time to the others, and unless the court orders otherwise the parties are jointly and severally liable for the expert's fees (CPR 35.8).
  • Expert advisor. An expert instructed only to advise, before proceedings or to comment on a single joint expert's report, is acting as an advisor. The CJC guidance applies once they are instructed to prepare or give evidence.
  • MedCo reports. In low value road traffic whiplash and soft tissue claims, the first fixed cost medical report must come from an accredited medical expert selected through the MedCo Portal (Practice Direction 35, para 2.6).

What solicitors look for when they choose an expert is covered in what instructing solicitors actually want from an expert report.

How do you become an expert witness in the UK?

There is no formal route, but most medical experts follow a similar path:

  • Clinical standing. Solicitors instruct experts for their experience, so the starting point is substantial experience in the specialty and an active clinical practice.
  • Training in the rules. Courses on Part 35, report writing and giving evidence are run by organisations including Bond Solon, the Expert Witness Institute and the Academy of Experts, and some lead to certificates. None is compulsory.
  • Professional guidance. Doctors should read the GMC's guidance Providing witness statements or expert evidence as part of legal proceedings, in effect since 30 January 2024, which builds on Good medical practice.
  • Indemnity. Since Jones v Kaney an expert witness can be sued by the party who instructed them, so check that your indemnity covers medico-legal work.
  • Instructions. Expert directories and registers, medical reporting organisations and referrals from solicitors are the usual sources of work. For whiplash reports, MedCo accreditation means registering, completing the online accreditation training and keeping up annual CPD.
  • Systems. Plan for secure handling of confidential records, deadlines running across many cases at once, and time recording that supports the fee note.

How are expert witnesses paid, and who pays?

The instructing party pays the expert, on terms of appointment that the CJC guidance says should be agreed at the outset: the basis of charges (an hourly or daily rate with an estimate of time, or a fixed fee), fees for attending court, cancellation charges and when payment is due. A single joint expert is paid by the instructing parties together.

Rates vary with the specialty, the expert's seniority and the complexity of the case, and there is no national scale for privately funded civil work. Some work has fixed or capped fees: first medical reports in whiplash and soft tissue claims carry fixed recoverable costs, and legal aid work is paid at rates set by regulation.

Three further points affect the fee. The court can limit the expert's fees that one party recovers from another (CPR 35.4(4)), so the estimate given when permission is sought matters. If an expert fails to answer a proper written question, the court can order that the instructing party may not recover the expert's fees from the other side (CPR 35.6(4)). And the CJC guidance (para 88) strongly discourages fees that depend on the nature of the evidence or the outcome of the case, quoting the court in Factortame (No 8) [2003] QB 381 that it would be "a rare case indeed" for a court to consent to an expert instructed on a contingency fee.

Can an expert witness be sued?

Yes. Until 2011 expert witnesses shared the immunity from suit that protects every witness. In Jones v Kaney [2011] UKSC 13 a claimant sued the clinical psychologist instructed on his behalf, alleging that a negligently prepared joint statement had forced him to settle his personal injury claim for much less than it was worth. The Supreme Court, by a majority, abolished the immunity from suit for breach of duty, in contract or in negligence, that expert witnesses had enjoyed in relation to their part in legal proceedings. The decision left the immunity from defamation claims in place, along with the immunity of other witnesses.

Regulators can act too. In General Medical Council v Meadow [2006] EWCA Civ 1390 the Court of Appeal held that witness immunity does not protect a doctor from fitness to practise proceedings over evidence given as an expert.

What makes a good expert witness?

The qualities courts look for follow from the duty. A good expert witness:

  • stays inside their expertise, and says so when a question falls outside it;
  • works from the complete record, and says what is missing (see what to do when the disclosure has gaps);
  • summarises the range of opinion and explains why they prefer their own, as paragraph 3.2(6) of Practice Direction 35 requires;
  • shows the reasoning, so a reader can follow how each conclusion was reached;
  • concedes the points that should be conceded, in the joint statement and in the witness box;
  • meets the deadlines in the court's directions.
Write the opinion you would give if the other side had sent you the same instructions. That is the test of independence the Civil Justice Council recommends, and it is a fair test of every paragraph in the report.

How ALLDOQ fits

An expert witness's opinion is only as strong as the record it rests on. ALLDOQ gives medico-legal experts one secure workspace for each instruction: the records and instructions in one place, imaging in the browser, a chronology with every entry linked to its source page, a report builder and time recording for the fee note. Book a walkthrough to see it on a real instruction.

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