Expert evidence: an overview

by Practical Law Dispute Resolution

Expert evidence is crucial for assisting the court on matters on which it does not have the requisite technical or specialist knowledge. This Practice note provides an overview of the rules, guidance, and key issues to consider when instructing an expert witness in civil litigation. It explores how to find and appoint a suitable expert, the types of cases where such evidence is commonly required and the different ways experts may be used, explaining the difference between an expert witness and an expert advisor. It also details experts' duties to the court under CPR 35, as supported by the Civil Justice Council (CJC) Guidance. The note covers the requirements for the form, content, and timing of experts' reports, their evaluation and expert evidence at trial. It also reviews recent developments, including the impact of AI on expert evidence and, separately, the introduction of the Public Domain Documents Pilot, which will run from 1 January 2026 until 31 December 2027, under PD 51ZH. Experts' reports, their annexes and exhibits are included within the ambit of the pilot, which applies to documents entering the public domain through a public hearing and will apply in the Commercial Court, London Circuit Commercial Court and Financial List.