Expert Evidence CASES

In English law, expert evidence is opinion evidence given by a qualified expert to help the court decide issues that require specialist knowledge. The expert’s role is not to argue a party’s case, but to give independent assistance on technical, scientific, medical or other specialised matters. Courts control the use of expert evidence closely to ensure it is necessary, reliable and proportionate.

What makes evidence “expert”

Expert evidence is allowed where the court cannot properly decide an issue using ordinary knowledge alone. The expert must have relevant qualifications or experience, and must stay within their area of expertise. Crucially, the expert owes a duty to the court, not to the party who instructs or pays them. Opinions must be reasoned and explained; bare conclusions or advocacy are not acceptable.

Procedure and control

In civil cases, parties usually need the court’s permission to rely on expert evidence. The court may limit the issues experts can address, the number of experts, or require a single joint expert. Experts are often required to meet, identify points of agreement and disagreement, and explain the reasons for any differences. The court may also ask written questions or hear experts together at trial.

Common areas

Expert evidence is common in medical negligence and personal injury cases, construction and engineering disputes, valuation and accountancy claims, intellectual property cases, and family proceedings involving welfare, capacity or risk. What matters is not the label of the discipline, but whether the evidence genuinely helps the court resolve a live issue.

Problems and limits

Courts are cautious about expert evidence. It may be excluded or given little weight if the expert strays outside their expertise, fails to explain their reasoning, relies on weak data, or shows partisanship. Evidence that adds cost and complexity without real assistance will not be allowed. Proportionality is key.

Practical importance

For parties, the focus should be on identifying exactly what expert help is needed and why. Instructions should be clear, neutral and focused on the issues. Experts should be given all relevant material, including anything that undermines the case. For opponents, careful scrutiny of the expert’s independence, reasoning and scope often provides effective grounds for challenge.