Expert witnesses occupy a peculiar position in English litigation: engaged and paid by one side, but owing their overriding duty to the court under CPR Part 35 and Practice Direction 35. For most of the twentieth century that dual role came with a substantial protection — witness immunity. The Supreme Court's decision in Jones v Kaney [2011] UKSC 13 removed that protection for party-appointed experts, and the PI landscape changed with it.
Before Jones v Kaney, the principal authority was Stanton v Callaghan [2000] QB 75, which extended witness-of-fact immunity to expert witnesses for evidence given in court and work sufficiently connected to it, including the joint statement following experts' discussions. A dissatisfied client had no cause of action against the expert. The justification was the public interest in candid expert evidence, unfettered by fear of subsequent litigation.
In Jones v Kaney [2011] UKSC 13 the Supreme Court, by five to two, held that the immunity of party-appointed experts from suit by their instructing party could no longer be justified. Dr Kaney, a clinical psychologist instructed for Mr Jones in a personal injury claim, signed a joint statement said to be materially inconsistent with her earlier reports; Mr Jones's claim was settled at a lower figure and he sued her. The Supreme Court held the claim could proceed. Party-appointed experts are now exposed to negligence claims by the party who instructed them, in the same way as any other professional adviser.
The abolition in Jones v Kaney was directed at party-appointed experts. Experts appointed by the court itself — including certain single joint experts under CPR 35.7, and experts assisting the court in family proceedings — may retain a narrower residual immunity, on the footing that they perform a quasi-judicial function. The point has not been finally resolved and is fact-sensitive. Practitioners acting predominantly in court-appointed capacities should not assume the immunity holds.
Notified claims since 2011 fall into recurring patterns. The first is inadequate methodology — measurements not taken, comparables not considered, calculations not shown, standard tests not performed. The second is missed considerations — a material factor overlooked, or a change of position at joint statement stage without a documented reason. The third is biased or partisan opinion — an expert crossing the line from independent opinion into advocacy, contrary to CPR 35.3.
Traditional professional indemnity cover for a surveyor, accountant, engineer or medical practitioner will generally respond to expert-witness work, provided that activity falls within the description of the insured's professional business on the schedule. Wordings vary, and some insurers apply endorsements or sub-limits to expert-witness work — particularly where it forms a substantial portion of the practice, or where the practitioner acts in high-value commercial litigation. A practitioner who has taken on expert-witness instructions since renewal should check whether disclosure is required under the policy's fair-presentation provisions.
The requirements of CPR Part 35 and Practice Direction 35 — the statement of truth, the declaration of the expert's duty to the court, the record of instructions, and the disclosure of literature relied on — are not merely procedural. They are, in practice, the expert's first line of defence when a claim is intimated. A report that complies fully with PD 35 paragraph 3 and documents the basis of every opinion is materially harder to characterise as negligent than one that does not.
Worked example (illustrative only). A chartered surveyor is engaged in 2024 as a party-appointed expert in a boundary and diminution-of-value dispute. The report supports the instructing client's case on quantum. At trial the judge prefers the opposing expert's methodology and the claim fails. The client — the surveyor's own instructing party — later intimates a claim in negligence, alleging that the methodology ignored a material comparable and departed from RICS guidance. Pre-2011 the claim would not have got off the ground: expert-witness immunity would have barred it. Post-Jones v Kaney the claim proceeds. The surveyor notifies the PI insurer, which appoints panel solicitors to defend, and — if liability is established — the policy responds to indemnify the settlement or judgment, subject to excess and limit.
A practitioner taking expert-witness instructions should confirm in writing with their broker that cover extends to expert-witness work, and check whether any sub-limit or endorsement applies. Sole practitioners in disciplines that see high volumes of litigation — forensic accountancy, construction, medical, valuation — should consider whether the limit of indemnity is proportionate to the values in dispute. Retired professionals who continue to accept expert instructions should confirm that run-off cover is in place.
For sector-specific PI considerations see Apex's pillars for surveyors' PI insurance, accountants' PI insurance, engineers' PI insurance, and architects' PI insurance.
Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority. Firm reference number 724952. This entry is general information, not advice on any particular policy.