Expert witness
A specialist appointed to give the court an independent opinion on a technical matter outside the judge's own knowledge.
Definition
An expert witness is a person with specialist knowledge, skill, or experience in a field relevant to the issues in a case who is appointed to assist the court by providing an opinion on technical matters. Unlike a factual witness who gives evidence of what they observed, an expert gives opinion evidence — for example, a medical expert on the extent of injuries, a surveyor on the value of a property, or an accountant on the calculation of losses. In civil proceedings in England and Wales, expert evidence is governed by CPR Part 35. Experts owe their overriding duty to the court, not to the party who instructs them. Courts frequently limit the number of experts and may appoint a single joint expert (SJE) to avoid duelling expert reports.
In practice
In small claims, expert evidence is rarely permitted without the court's specific permission — the costs are usually disproportionate. In fast-track and multi-track cases, the parties often start with without-prejudice discussions between their respective experts to narrow the issues before the hearing. An expert who overstates their case or advocates for their instructing party rather than the court loses credibility quickly. Instruct experts early — a late expert report can be excluded.