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Changing expert witness only allowed on disclosure of previous expert’s views

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22 September 2021

The English court does not like expert shopping. If a party seeks permission to change its expert, the court is likely to order disclosure of documents evidencing the previous expert’s views as the ‘price’ of the change, even where that would require a party to waive privilege. The jurisdiction to make such an order can stretch back to an expert instruction given before the pre-action protocol: Matthew Rogerson (t/a Cottesmore Hotel, Golf and Country Club) v Eco Top Heat & Power Ltd [2021] EWHC 1807 (TCC)

The dispute arose because of a fire at Cottesmore Hotel, Golf and Country Club in June 2018. The fire broke out while the defendant was installing windows at the hotel and the claimant alleged that it was caused by the defendant’s negligence. Specifically, the claimant said that one of Eco Top’s employees had probably started the blaze by discarding a cigarette. Eco Top denied the allegations.

Shortly after the fire, both parties retained experts to examine the site and establish the cause of the fire. The defendant’s expert was a Dr Nagalingam. The experts conducted joint site visits and interviewed witnesses, following which they continued to discuss a number of queries arising from their investigation. Dr Nagalingam did not prepare an expert report, but did provide his expert views on causation to the defendant’s solicitors in October 2018, which were recorded in a privileged attendance note.

The claimant issued proceedings in August 2020. At the directions stage, the defendant sought permission to rely on expert evidence as to the cause of the fire. However, rather than continuing with Dr Nagalingam, the defendant sought to appoint another expert: a Ms Wilson. The claimant did not oppose the defendant’s choice of Ms Wilson. Instead, it applied for disclosure of various categories of documents concerning Dr Nagalingam’s work as the condition (or ‘price’) of the defendant’s change of experts.

Mr Alexander Nissen QC, sitting as a High Court Judge, granted the application, ordering disclosure of the privileged attendance note setting out Dr Nagalingam’s views on causation. He identified two key principles in exercising the court’s discretion.

A true change of expert?

The defendant opposed the application, stating that Dr Nagalingam had been instructed in the immediate aftermath of the fire for the purposes of taking private advice on the matter, before engaging in the pre-action protocol. As such, the defendant’s instruction of Ms Wilson was not really a change of expert. The court was unconvinced by these submissions.

Disclosure of expert reports prepared before the commencement of proceedings, where the expert is not instructed to prepare a report for the court, will not usually be ordered unless there are unusual factors at play. However, although Dr Nagalingam had been instructed prior to the pre-action protocol, the extent of his engagement and of his collaboration with the claimant’s experts went further than that of an expert simply employed to provide a private assessment of the matter.

In the absence of any convincing evidence from the defendant to the contrary, the court inferred that Dr Nagalingam had been instructed by the defendant to advise on the litigation, such that the defendant’s decision to instruct Ms Wilson did constitute a change of expert.

The court’s discretion to order disclosure

The court held that, when determining whether to attach conditions to a party’s change of expert witness, such as disclosure of the previous expert’s report, there was “a sliding scale with flagrant expert shopping at one end and an unexpected need to replace the expert for objectively justifiable reasons at the other”. The closer the circumstances to the former, the more likely the court would be to impose significant conditions on its approval of the change, such as the waiver of privilege over a document.

The court further held that its determination of whether expert shopping had taken place would “almost always have to be one reached by inference”: given the court’s express aversion to the practice, it is “hardly likely to be patent or admitted”. In Rogerson, the court found that such an inference could be drawn on the facts of the case, namely:

  • The defendant did not disclose its retainer with Dr Nagalingam, which could have provided clarity on the nature of his instruction. In fact, the defendant had initially sought to imply that Dr Nagalingam was actually instructed by a third party (an implication the court found to be incorrect).
  • The defendant initially denied that Dr Nagalingam had expressed any expert view on causation, either to the defendant’s solicitors or to the claimant’s experts. The defendant subsequently conceded that an expert view had been given to its solicitors, and did not deploy any evidence to suggest that such a view had not been given to the claimant’s experts.
  • Dr Nagalingam was an appropriate expert to act in the matter and was as well qualified as Ms Wilson.

The court therefore concluded that this was a case of expert shopping, justifying disclosure of the privileged attendance note containing Dr Nagalingam’s views on causation as the ‘price’ for the change of expert.


Although instructing an expert at the early stages of a potential dispute can be vital in assessing the merits of the case, the court’s judgment in Rogerson is an important reminder of the possible pitfalls.

The importance of selecting an appropriate expert at the first attempt cannot be understated, as the court takes a consistently dim view of expert shopping. If a party instructs an expert and then wishes to change that expert, the court will likely require disclosure of the original expert’s work as the ‘price’ for approving that change. This can be the case even where the original expert is instructed before the pre-action protocol and can involve waiving privilege.

It is therefore vital to be clear about the scope of the instructions of any expert retained in the nascent stages of a dispute, and to canvass potential experts thoroughly and effectively before any instructions are given.

Further information

This case summary is part of the Allen & Overy Litigation and Dispute Resolution Review, a monthly publication. If you wish to receive this publication, please contact Amy Edwards.

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