Your Case Needs Expert Evidence — How to Instruct
Expert evidence in civil proceedings requires the court's permission. The court favours joint single experts. CPR Part 35 governs the duties and use of expert witnesses.
Quick Answer
You cannot simply instruct an expert and put their report before the court without permission — CPR r.35.4 requires you to obtain the court's consent specifying the field of expertise. Where possible, the court will order a joint single expert instructed by both parties. If you can instruct separately, the expert's overriding duty is to the court, not to the party paying them.
Full Explanation
CPR Part 35 and its accompanying Practice Direction govern the use of expert evidence in civil proceedings in England and Wales. The starting point is that no party may call an expert or put in an expert's report without the court's permission (CPR r.35.4). Courts control expert evidence tightly to keep costs proportionate and to avoid 'battles of experts' that delay trials and inflate costs.
Where expert evidence is genuinely necessary — for example, in a clinical negligence claim, a property valuation dispute, or a building defects case — the first step is to identify the specific field of expertise required and to raise it at the case management conference or by making an N244 application for permission to rely on expert evidence. The court's order will specify the field of expertise, often the deadline for exchange of reports, and whether experts are to meet.
The court's strong preference is for a single joint expert (SJE) appointed jointly by both parties. This is particularly common in lower-value claims and straightforward valuation cases. Where an SJE is ordered, both parties send a joint letter of instruction, the expert's report is disclosed simultaneously to both, and questions under CPR r.35.6 may be put by either party. An SJE's report is not binding on the court but carries significant weight.
Where separate experts are permitted — typically in higher-value cases or where the issues are genuinely contested — the experts are required by CPR r.35.12 to hold an experts' meeting and to produce a joint statement identifying agreed matters and issues still in dispute. This is an important procedural step: an expert who concedes points at the meeting without authority risks damaging the instructing party's case, so close preparation is essential.
The overriding duty of an expert witness is to the court, not to the party instructing them (CPR r.35.3). An expert who departs from this duty risks having their evidence excluded or being the subject of adverse comment. The letter of instruction should make this duty clear. It is good practice to refer the expert to the CPR Part 35 Practice Direction and to Appendix B of the Commercial Court Guide (or equivalent).
Legal Basis
- §CPR Part 35 — Experts and Assessors
- §CPR Practice Direction 35 — Experts and Assessors
- §CPR r.35.3 — Expert's overriding duty to the court
- §CPR r.35.4 — Court's power to restrict expert evidence
- §CPR r.35.6 — Written questions to experts
- §CPR r.35.12 — Discussions between experts
What To Do
Identify the Expert Field Required
Define precisely what expertise is needed — for example, 'a consultant orthopaedic surgeon' or 'a RICS-qualified building surveyor'. Courts grant permission by reference to a specific field, not a named individual.
Seek the Court's Permission
At the case management conference (or by N244 application), apply for permission to rely on expert evidence in the identified field. Explain why expert evidence is necessary and proportionate, and indicate whether you propose a joint or separate expert.
Instruct a Joint Expert if Ordered
If the court orders a single joint expert, work with the other party to agree a suitable expert and send a joint letter of instruction. The letter should be balanced and agreed — avoid asking leading questions that could be seen as seeking to influence the expert.
Draft a Proper Letter of Instruction
The letter of instruction should set out the background facts, the agreed chronology, the specific questions for the expert to answer, and a clear statement that the expert's duty is to the court. Attach relevant documents. The letter will be disclosed to the other side.
Facilitate the Experts' Meeting
If separate experts are instructed, ensure they meet (or correspond) in accordance with the court's directions. Prepare your expert thoroughly for the meeting. Review the joint statement carefully — any concessions made may be difficult to withdraw.
Use CPR r.35.6 Questions Judiciously
Either party may put written questions to the other's expert (or to a joint expert) within 28 days of service of the report. Questions must be for the purpose of clarification only — not a further cross-examination. Unanswered questions may disentitle the other party from relying on the report.
Important Deadlines
Important Warnings
Commissioning an expert report before obtaining court permission risks the report being inadmissible and the costs being disallowed as wasted.
An expert who strays into advocacy — for example, by expressing opinions on legal questions or overstating the strength of the case — will be criticised by the court and may undermine your entire case.
Expert shopping (seeking opinions from multiple experts and only disclosing the favourable one) is improper and, if discovered, will likely result in serious costs consequences and adverse findings.