The Civil Procedure Rules (CPR) defines an expert in general terms as a “person who has been instructed to give or prepare expert evidence for the purpose of proceedings”. A “single joint expert” is an expert instructed to prepare a report for the court on behalf of two or more of the parties (including the claimant) to the proceedings. When making decisions in negligence claims, the courts rely heavily on the advice and opinions of the experts, and in clinical negligence claims this is provided by clinicians. Experts should be used appropriately, and their duty is always to the court rather than as an advocate of either party. But as medicine is not an exact science, often there will be a difference of opinion even with the views of experts.