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Fiduciary duties of expert witnesses?

14th Jul 2020 | Construction & Engineering
Fiduciary duties of expert witnesses?

A v X (2020) EWHC 809 TCC; BLM;  O’Farrell J


The claimant was developing a petrochemical plant in Abu Dhabi. It contracted for the design with Company C and for the construction with Company B.  The claimant hired the defendants as its expert witness to defend when Company B brought an arbitration claim for delay costs.

Separately, Company C also sued the claimant in arbitration for design fees. When the claimant learned that C was planning to hire the defendants as its expert also, it applied for an injunction against the defendants to stop this.

The defendants argued that they would not be using any confidential information of the claimant when advising C, and therefore did not have a conflict. The claimant argued that the defendants ordered a duty of loyalty (or a “fiduciary duty”) in any event.


The nature of the defendants’ relationship with the claimants - necessarily providing advice and support throughout major arbitration proceedings - was sufficient to create a clear relationship of trust and confidence.

Therefore, the defendants owed a fiduciary duty to the claimant, and could act not for the claimants in one aspect of this complex dispute, and against them in another.

Where an expert’s contract has been terminated, or where the relationship is not one that creates a fiduciary or loyalty duty, then the expert can act for another party in the case, as long as the duty to preserve confidential information is observed.


The developer was no doubt dismayed when its professional advisers, on their large and worrying dispute, announced that they were going to be acting against it in support of the designers’ claim.

Although the court supported their injunction claim, it would be wise to write an express commitment not to act both for and against the client into any future professional appointment.

For more specialist legal advice please get in touch with Lucilla Waugh on 0191 211 7984 or email [email protected]

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