Experts occasionally assume that once they have accepted an appointment, their evidence is entirely beyond challenge — protected by a form of professional immunity that shields them from any consequence arising from the opinions they give. That assumption is not entirely wrong, but it is considerably narrower than many experts believe, and understanding its actual boundaries matters both for experts giving evidence and for clients relying on them.
The rationale for immunity
The underlying policy reason for extending some form of immunity to expert witnesses is straightforward: if experts could be sued by the party who instructed them every time their evidence proved unfavourable, or was rejected by the tribunal, the pool of professionals willing to give independent expert evidence would shrink considerably, and the evidence that remained would be shaped by defensive self-interest rather than genuine professional judgment. Some protection against this risk is generally considered necessary to preserve the independence the entire system of expert evidence depends upon.
Historically, this protection extended quite broadly — covering not only evidence given in the tribunal itself but also the preparatory work underlying that evidence. In several major common-law jurisdictions, however, the scope of that immunity has narrowed significantly over the past decade or more, with courts increasingly willing to hold experts accountable for negligent preparatory work even where the resulting evidence itself retains some protection. Practitioners should treat immunity as a real but genuinely limited protection, not as a blanket shield against all professional consequence.
What immunity typically does cover
Where it applies, expert witness immunity generally protects an expert from liability in relation to:
- The content of evidence actually given to the tribunal, whether in a written report or orally
- Statements and opinions expressed in the course of, and closely connected to, the tribunal proceedings themselves
What immunity typically does not cover
Immunity is not, and has increasingly not been treated as, a shield against liability for:
- Negligent preparatory work underlying the eventual evidence — for example, a fundamentally flawed methodology, a failure to properly investigate matters within the expert's competence, or careless handling of the underlying facts, even where the resulting report was ultimately presented to the tribunal
- Breach of the expert's contractual duty to the instructing client, including obligations around competence, timeliness, and the basic standard of professional care owed under the terms of engagement
- Disciplinary consequences arising from a failure to comply with the professional or institutional standards governing the expert's conduct — immunity from civil liability does not extend to protection from professional regulatory bodies assessing whether the expert met the standards their qualification requires
- Deliberate dishonesty or bad faith, which sits entirely outside any rationale immunity is intended to serve
Why this distinction matters in practice
For an expert, the practical lesson is that immunity — to the extent it applies at all in the relevant jurisdiction and forum — is not a reason to relax the rigour applied to preparatory work. The methodology, the document review, the site inspection, and the analytical process underlying the eventual opinion remain exposed to scrutiny and, potentially, liability, in a way the final evidence given to the tribunal may not be. An expert who treats "I gave my honest opinion" as sufficient defence for careless underlying work misunderstands where the actual protection, where it exists, is likely to lie.
For lawyers instructing experts, and for clients relying on that evidence, the practical lesson is not to assume that a poor-quality expert report carries no consequence for the expert simply because expert witnesses are broadly understood to enjoy some protection. Where an expert's preparatory failures have genuinely damaged a client's case — through negligent investigation, a fundamentally unsound methodology, or a failure to meet basic professional standards — that failure may well remain actionable, and is very likely to be a matter the expert's own professional or regulatory body would want to know about.
The jurisdictional dimension
Because the scope of immunity varies by jurisdiction and by the specific forum in which the evidence is given, experts and lawyers working across DIAC arbitration, the DIFC Courts, arbitrateAD, and other regional institutions should treat this as a question requiring specific legal advice on the applicable framework, rather than assuming a uniform position across the region. This is a point on which qualified legal advice, tailored to the specific forum and governing law, should be sought rather than relying on general professional understanding.
A grounding principle, not a loophole
The purpose of expert witness immunity, properly understood, is to protect the independence of genuine, competently prepared expert evidence — not to insulate careless or negligent work from any consequence. Experts who approach every stage of an engagement with the rigour set out across this series have little practical need to lean on immunity as a fallback, because the underlying work is unlikely to expose them to the liability from which immunity does not, in any event, fully protect.
Part 17 looks at how the major professional standards governing expert evidence — the CIArb Protocol, the RICS Practice Statement, and the IBA Rules on the Taking of Evidence — relate to one another, and what practitioners should do where they appear to diverge.