Expert Witness

CPR Part 35 gives the expert's overriding duty statutory force: rule 35.3 states that it is the duty of experts to help the court on matters within their expertise, and that this duty overrides any obligation to the person from whom experts have received instructions or by whom they are paid. Experts are not free agents in litigation, however — no party may call an expert or put in evidence an expert's report without the court's permission, and expert evidence generally must be restricted to that which is reasonably required to resolve the proceedings. Where two or more parties want expert evidence on the same issue, the court can direct that a single joint expert be instructed and shared between them rather than each side calling its own.

The formal content of an expert's report is also prescribed: it must comply with Practice Direction 35, and at the end of the report there must be a statement that the expert understands and has complied with their duty to the court. The report must also state the substance of all material instructions, written or oral, on which it was based — a safeguard against selective or misleading instruction of the expert, since the underlying instructions are not privileged from disclosure if the court has reasonable grounds to think the stated instructions are inaccurate or incomplete. Failure to observe these duties can affect whether the report is admitted, and the court may also limit or disallow recovery of an expert's fees from the other party.