CPR 35 is Part 35 of the Civil Procedure Rules, the part that governs expert evidence in civil claims in England and Wales. It is short: fifteen rules, supported by Practice Direction 35 and the Civil Justice Council's Guidance for the Instruction of Experts in Civil Claims (2014). Between them they decide whether an expert can be called at all, who the expert owes a duty to, what the report must say, and how the other side can test it. This guide goes through each rule in plain English, then sets out what a CPR 35 compliant report needs and how Part 35 questions work.

The practical bottom line

  • Permission comes first. No party may call an expert or put in an expert's report without the court's permission (CPR 35.4).
  • The duty runs to the court. An expert's duty to help the court overrides any obligation to the party who instructs or pays them (CPR 35.3).
  • The report has a fixed shape. Practice Direction 35 lists what it must contain, and it must end with a statement of understanding and a statement of truth in the prescribed wording.
  • Questions are limited. Written questions are put once, within 28 days of the report being served, and only to clarify it unless the court or the other side agrees otherwise (CPR 35.6).

What is CPR 35?

Part 35, titled "Experts and Assessors", applies to any expert instructed to give or prepare evidence for the purpose of civil proceedings. The definition in CPR 35.2 turns on the purpose of the instruction. A clinician asked only for private advice on the merits of a claim, with no view to their evidence going before the court, sits outside Part 35. Once they are instructed to prepare evidence for the proceedings, every rule applies.

One aim runs through all fifteen rules: expert evidence should help the court decide the issues, at a proportionate cost, from someone independent of the parties. Most of what follows is machinery for enforcing those three things.

What does each rule in Part 35 say?

  • 35.1, duty to restrict expert evidence. Expert evidence is restricted to what is reasonably required to resolve the proceedings.
  • 35.2, interpretation. Defines an expert and a single joint expert.
  • 35.3, the overriding duty. Experts must help the court on matters within their expertise, and that duty overrides any obligation to the person instructing or paying them.
  • 35.4, permission. The court's permission is needed to call an expert or use a report. The party applying must give an estimate of the costs and identify the field of expertise and, where practicable, the expert. The court can limit the fees recoverable from the other side.
  • 35.5, written reports. Expert evidence is given in a written report unless the court directs otherwise. On the small claims and fast tracks, the court will not direct an expert to attend a hearing unless that is necessary in the interests of justice.
  • 35.6, written questions. Covered in detail below.
  • 35.7, single joint experts. Where two or more parties want expert evidence on the same issue, the court can direct that one expert gives it.
  • 35.8, instructions to a single joint expert. Each instructing party may give instructions, copied to the other parties. Unless the court directs otherwise, the instructing parties are jointly and severally liable for the expert's fees and expenses.
  • 35.9, information. The court can order a party to provide information that is available to them and not reasonably available to the other side.
  • 35.10, contents of the report. The report must comply with the practice direction, confirm the expert understands and has complied with their duty, and state the substance of all material instructions, written or oral. Those instructions are not privileged, but the court will only order their disclosure, or allow cross-examination on them, if there are reasonable grounds to think the statement of instructions is inaccurate or incomplete.
  • 35.11, use of a disclosed report. Once a party has disclosed a report, any party can use it as evidence at trial.
  • 35.12, discussions between experts. The court can direct the experts to discuss the issues and produce a statement of what they agree, what they disagree on, and why. The content of the discussion cannot be referred to at trial unless the parties agree, and an agreement between experts does not bind the parties unless they expressly agree to be bound.
  • 35.13, failure to disclose. A party who does not disclose a report cannot use it at trial or call the expert without the court's permission.
  • 35.14, the expert's right to ask for directions. An expert can file a written request to the court for directions. Unless the court orders otherwise, they must send the proposed request to the instructing party at least 7 days before filing it, and to all other parties at least 4 days before.
  • 35.15, assessors. The court can appoint an assessor to help it on a matter in which the assessor has skill and experience.

What does Practice Direction 35 add?

The practice direction turns the rules into working standards. Paragraph 2 sets the expert's conduct. Evidence should be the independent product of the expert, uninfluenced by the pressures of litigation. The expert should give an objective, unbiased opinion, keep out of the role of advocate, and consider all material facts, including those that detract from their opinion. They should say when a question falls outside their expertise and when an opinion is provisional because the research or the data is incomplete, and tell all parties promptly if their view changes.

Paragraph 3 sets the contents of the report, covered in the checklist below. Paragraph 6 deals with questions: they are sent to the expert with copies to the other parties, and the party who instructed the expert pays for the answers, whatever the court later decides about who ultimately bears the cost. Paragraph 7 covers single joint experts, paragraph 9 the discussions between experts and the joint statement, and paragraph 11 concurrent evidence, where experts give their evidence together in one session.

What makes a report CPR 35 compliant?

A CPR 35 compliant report, often called a Part 35 compliant report, is one that meets CPR 35.10 and paragraph 3 of the practice direction. Check the report against this list before it is signed:

  • It is addressed to the court.
  • It gives details of the expert's qualifications.
  • It lists the literature and other material relied on.
  • It states the substance of all facts and instructions that are material to the opinions or on which they are based.
  • It makes clear which facts are within the expert's own knowledge.
  • It says who carried out any examination, measurement or test the expert relied on, their qualifications, and whether it was done under the expert's supervision.
  • Where there is a range of opinion, it summarises the range and gives reasons for the expert's own view.
  • It contains a summary of the conclusions.
  • It states any qualification to an opinion the expert cannot give without one.
  • It contains a statement that the expert understands their duty to the court, has complied with it, and is aware of the requirements of Part 35, the practice direction and the 2014 Guidance.
  • It ends with a statement of truth in the prescribed form.

The statement of truth for an expert report reads: "I confirm that I have made clear which facts and matters referred to in this report are within my own knowledge and which are not. Those that are within my own knowledge I confirm to be true. The opinions I have expressed represent my true and complete professional opinions on the matters to which they refer. I understand that proceedings for contempt of court may be brought against anyone who makes, or causes to be made, a false statement in a document verified by a statement of truth without an honest belief in its truth." The final sentence was added in April 2020, and older templates often leave it out. Copy the wording from the practice direction itself.

For the order of sections and how to write each one, see our structure-first guide to writing an expert witness report.

Almost every compliance failure under Part 35 comes back to one question the report leaves unanswered: how would a reader check this?

How do Part 35 questions to experts work?

CPR 35.6 lets a party put written questions about a report to an expert instructed by another party, or to a single joint expert. The limits are tight:

  • Questions may be put once.
  • They must be put within 28 days of service of the report.
  • They must be only for the purpose of clarifying the report, unless the court gives permission or the other party agrees.
  • They go to the expert directly, with copies to the other parties.

The expert's answers are treated as part of the report. If the expert does not answer, the court can order that the party who instructed them may not rely on that expert's evidence, or may not recover the expert's fees from any other party.

Experts answering questions should keep three habits. Answer every question under its own number. Stay inside your expertise, and say so plainly when a question moves outside it. And if a question goes beyond clarifying the report, raise it with your instructing party before answering, because they may want to object or agree to it. An answer that shifts your opinion is a change of view under paragraph 2 of the practice direction, and every party needs to know.

When does the court order a single joint expert?

Under CPR 35.7 the court can direct that evidence on an issue comes from one expert instructed jointly by the parties. It is common where an issue is narrow or largely technical, such as some care and quantum questions, and in lower value claims where two experts would be disproportionate. If the parties cannot agree who to instruct, the court can choose from a list they prepare or direct another way of selecting the expert.

A single joint expert owes the same duty to the court as any other expert. The 2014 Guidance adds a practical rule: a single joint expert should not attend a meeting or conference with only one party unless all parties have agreed in writing or the court has directed it.

What happens when an expert breaches Part 35?

A report that does not comply can be given little weight or excluded, and the court can make costs orders that reflect the waste. In Phillips v Symes [2004] EWHC 2330 (Ch) the court held that it has power to order costs against an expert whose evidence shows a flagrant disregard of their duties to the court. In Jones v Kaney [2011] UKSC 13 the Supreme Court ended expert witnesses' immunity from negligence claims by their own clients. And an expert who verifies a report they know to be false can be committed for contempt of court, as the Court of Appeal confirmed in Liverpool Victoria Insurance Co Ltd v Zafar [2019] EWCA Civ 392. Professional regulators such as the GMC can act on the same conduct.

Where to go next

Part 35 runs through every stage of an instruction. Our practical refresher on the expert's duty to the court covers CPR 35.3 in depth, the joint statement checklist covers discussions under CPR 35.12, and can an expert witness use AI? covers what the rules mean for AI-assisted reports. If you are new to the work, what is a medico-legal report? explains the main types of report and how each is used in a claim.

How ALLDOQ fits

Most Part 35 requirements come down to traceability: what you were sent, what you relied on, which facts are your own and where each one came from. ALLDOQ keeps the records, the chronology and the report in one workspace, with every entry tied to its source page, so the list of material relied on and the statement of instructions build up as you work. To see it on a live instruction, book a walkthrough.

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