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Expert Evidence

Expert evidence is important and can help prove a claim or disprove allegations, especially where the case involves matters on which the court does not have the requisite technical or academic knowledge, or the case involves issues of foreign law. Unlike witnesses of fact, a qualified expert is permitted to give opinion evidence on any relevant matter.

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The information published on this website is: (a) for reference purposes only; (b) does not create a contractual relationship; (c) does not constitute legal advice and should not be relied upon as such; and (d) is not a complete or authoritative statement of the law. Specific legal advice about your circumstances should always be sought.

What evidence is required in litigation?

To succeed in litigation, the claimant will need to prove his case on a balance of probabilities. To do this, the claimant must adduce evidence to support all the essential ingredients of the claim. The defendant will also need to adduce evidence to support his defence to some or all of the essential ingredients of the claim.

The evidence is usually comprised of:

  • Contemporaneous documents (hard copy or electronic versions or both) intended to prove the issues in dispute.
  • The evidence of factual witnesses, to tell the story behind the dispute and to fill in any gaps that the documents leave.
  • Expert evidence (where appropriate and permitted by the court which has a duty to restrict expert evidence to that which is necessary to determine the dispute), to assist the court when the case involves complex technical, academic or foreign law issues.

What kind of evidence goes in a witness statement?

The parties usually exchange written statements containing the evidence of their factual witnesses. The time period for exchanging witness statements will be agreed by the parties or ordered by the court at the CCMC. The court may also give directions identifying or limiting the witnesses who may give evidence, the issues that may be addressed and the length and format of witness statements.

The witness statements normally stand as the evidence in chief and a witness may be called to trial to be cross-examined on their statement. A witness statement must:

  • Be in the witness’s own words, if practicable.
  • Indicate which of the statements in it are made from the witness’s own knowledge and which are matters of information or belief and state the source of those matters.
  • Include a statement of truth, namely a statement by the witness that they believe the facts in the witness statement are true.

There are penalties for signing a statement of truth without an honest belief in the truth of the facts being verified.

Expert Evidence

The rules governing expert evidence are found in CPR 35:

Experts – overriding duty to the court

(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.

CPR 35(3)

An expert witness may give evidence on, for example, technical or scientific matters, or specialist practice or procedure. They may give their opinion on specific matters in the dispute within their expertise. However, it is not the function of an expert witness to give their opinion on issues of law or fact which the judge or jury has to decide.

Do I need the court’s permission to call expert evidence?

Yes. The court’s permission to call expert evidence is always required as the court has a duty to restrict expert evidence to that which is necessary to resolve issues in the proceedings. When applying for expert evidence to be allowed, the parties must apply early in proceedings (otherwise the court may later refuse due to timetabling issues), identify the expert by name or by field of expertise, specify the issues that he will address and estimate the cost of the expert evidence.

If it grants permission, the court will limit the evidence to the named expert or field ordered, and may specify the issues that the expert should address. Oral expert evidence at trial may only be given with the court’s permission.

Court’s power to restrict expert evidence

(1) No party may call an expert or put in evidence an expert’s report without the court’s permission.

(2) When parties apply for permission they must provide an estimate of the costs of the proposed expert evidence and identify –

(a) the field in which expert evidence is required and the issues which the expert evidence will address; and

(b) where practicable, the name of the proposed expert.

(3) If permission is granted it shall be in relation only to the expert named or the field identified under paragraph (2). The order granting permission may specify the issues which the expert evidence should address.

CPR 35(4)

What is a single joint expert?

The court may order that expert evidence is to be given by a single joint expert, namely an expert who is instructed on behalf of both parties. However, this is not common in multi-track cases.

Parties may instruct another expert to assist them, but any evidence from that expert will not be admissible and the costs of instructing that expert will not be recoverable from the other side.

What is an expert report?

Expert evidence is usually given in the form of a written report, which must be the independent product of the expert. The expert’s overriding duty is to the court and not to the party that instructed him. Expert reports are often exchanged simultaneously. However, in some cases, expert reports may be exchanged sequentially.

Contents of report

(1) An expert’s report must comply with the requirements set out in Practice Direction 35.

(2) At the end of an expert’s report there must be a statement that the expert understands and has complied with their duty to the court.

(3) The expert’s report must state the substance of all material instructions, whether written or oral, on the basis of which the report was written.

CPR 35.10

What is the procedure following the simultaneous exchange of expert reports?

Following the exchange of expert reports, a party may put questions to the other party’s expert for the purpose of clarifying his report. Questions must normally be put within 28 days of service of the report.

The court will usually direct there be a discussion between the experts for the purpose of requiring the experts to:

  • Identify and discuss the expert issues in the proceedings.
  • Where possible, reach an agreed opinion on those issues.

The court may direct that, following a discussion between the experts, they must prepare a statement for the court setting out those issues on which they agree, disagree, or both; with a summary of their reasons for disagreeing.

Must expert evidence be relevant to the issues?


It is self evident that expert evidence must be relevant to the issues to be decided by the court. For an example of the application of this principle to the question of expert medical evidence in a professional negligence action by a deceased miner’s estate against solicitors for the loss of a chance of pursuing a services claim in the context of the Department for Trade and Industry’s tariff-based compensation scheme for vibration white finger, see Edwards v Hugh James Ford Simey (A Firm) [2019] UKSC 54.

Can covert recordings be taken of an expert’s examination of a party?

In the personal injury case of Mustard v Flower [2019] EWHC 2623 (QB), the court allowed a party who had covertly filmed her examination by the defendant’s experts to adduce the recordings in evidence on the basis that, although her actions lacked transparency, the recordings were not unlawful, as they were relevant to the issues in the case and were probative and the Overriding Objective favoured their admission into evidence 

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