It is often the case that commercial disputes call for expert advisors; one category ‘clean’, who are independent, jointly or separately appointed, and with an overriding duty to the court or tribunal; and those sometimes described as ‘dirty’, with no overriding duty to the court and who are called in to advise one side specifically, often in the background. Both can play key and distinct roles, but the importance of defining those roles and the strategy behind them can be crucial, particularly as experts can and do change during the course of a long litigation.

Construction lawyers in the firm’s Dispute Resolution group were instructed by a new build insurer in connection with a substantial multi-party recovery action arising from remedial work at a large residential flat development. The claim dated back many years and involved detailed technical allegations.

With expert evidence expected to be crucial, an issue arose at case management stage over whether one side, having instructed one expert and then another on the same issue, both of whom had been (outwardly, and at different times) involved in without prejudice discussion and exchanges of reports as formal ‘experts’, should have permission to rely on their latterly appointed expert only on condition that disclosure of the earlier expert’s views be given.

That order was made, which is not unusual. However, where both ‘experts’ remained instructed but with the former now standing only in an advisory capacity, the Court had to consider the extent of the disclosure obligation it imposed. In circumstances where it could not readily be shown when in time the former expert’s role had transitioned from ‘clean’ to ‘dirty’, acting as advisor in the background, the disclosure order given caught almost all of the first experts’ expressed opinions as well as written reports generated from the outset. The implication of that condition was strategically significant for obvious reasons.

The present case was successfully resolved with the parties reaching agreement at mediation, but whether in litigation or arbitration, the issue of expert-related disclosure serves to highlight the importance of an early strategic approach to expert instruction, particularly when appointing and utilising advisors.

If you have any questions or wish to discuss an issue, please contact the Dispute Resolution Group on 01753 889995 or email

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