Guide
Expert evidence: permission, cost estimates and what a report must say
Updated
The rules that govern expert evidence are also, in practice, cost control rules. Reading them before instructing tends to save more than negotiating the rate afterwards.
Expert evidence is permitted, not assumed
CPR rule 35.1 restricts expert evidence to that which is reasonably required to resolve the proceedings, and rule 35.4(1) provides that no party may call an expert or put in evidence an expert's report without the court's permission. Rule 35.4(2) requires a party applying for permission to provide an estimate of the costs of the proposed expert evidence and to identify the field in which it is required, the issues it will address and, where practicable, the name of the proposed expert. Permission, if granted, is only in relation to that expert or that field (justice.gov.uk).
What that means when you take a quote
- The estimate has a job to do. It is not simply a commercial indication: it goes before the court and informs whether permission is granted at all.
- Scope is defined at the permission stage. The issues the expert evidence will address are identified then, which is another reason to frame the questions carefully before instructing.
- Proportionality is live. Rule 35.1 exists to stop expert evidence that the dispute does not justify, so an estimate that is large relative to the sum at stake is a problem before it is an expense.
- On the small claims and fast tracks, rule 35.4(3A) provides that permission for expert evidence will normally be given for only one expert on a particular issue.
What the report itself must contain
Rule 35.10(1) requires an expert's report to comply with the requirements set out in Practice Direction 35 (justice.gov.uk). Rule 35.10(2) requires a statement at the end of the report that the expert understands and has complied with their duty to the court. Rule 35.10(3) requires the report to state the substance of all material instructions, written or oral, on the basis of which it was written, and rule 35.10(4) provides that those instructions are not privileged against disclosure. A report that does not meet these requirements may have to be revised, which is a cost with no benefit.
The stages after the report
- Written questions, rule 35.6
- A party may put written questions to an expert about their report, for the purpose of clarification unless the court gives permission or the other party agrees otherwise.
- Discussions between experts, rule 35.12
- The court may direct a discussion between experts to identify and discuss the expert issues and, where possible, reach an agreed opinion, and may direct that they prepare a statement setting out what is agreed and what is not with reasons.
- Use of a disclosed report, rule 35.11
- Where a party has disclosed an expert's report, any party may use it as evidence at trial. That is worth understanding before commissioning a report you may not like.
- The expert's own route to the court, rule 35.14
- Experts may file written requests for directions to assist them in carrying out their functions, subject to the notice periods in that rule.
Part 35 governs civil proceedings. Expert evidence in family proceedings is governed by Part 25 of the Family Procedure Rules, which similarly requires the court's permission and controls the cost of expert evidence. This page is general information about the rules, not legal advice on your case.