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Costly consequences of a party getting too close to their expert

The costly consequences of a party getting too close to their expert have been spelt out in a recent case. The High Court revoked permission for the Claimants to rely on their expert in the Chirk Nuisance Group Litigation leaving them late in the litigation having to seek a new expert and begin again in terms of expert evidence.


A claim has been brought by a number of North Wales’ residents in Chirk who allege that the Defendant, Kronospan Ltd, is liable to them in public or private nuisance by reason of dust, noise or odour emissions from its wood processing and wood product manufacturing plant. If successful, the Claimants seek an injunction or declaration preventing the nuisance together with damages.

The facts

The expert, Dr Nigel Gibson, was instructed by the Claimants as a dust modelling expert.

The experts for both sides were due to meet between May and November 2021. Following a chain of correspondence between the parties’ representatives, it became apparent that during that period there had been ongoing communications between Dr Gibson and the Claimants’ representatives. The content of those communications included draft versions of the joint statement being provided to the Claimants’ representatives and advice and suggestions by the representatives as to what should be contained in the joint statement.

Following disclosure of those communications, the Defendant applied to the Court to revoke the Claimants’ permission to rely on Dr Gibson as an expert witness. Whilst the Claimants agreed that there had been a breach of the Rules (with the Claimants’ representatives admitting to at least 16 comments relating to “advice and suggestions as to content”), the main point of contention between the parties was the sanction to be applied, with the Claimant arguing that the revocation of permission would be “potentially disastrous” due to significant additional costs and delay.

The decision

Due to the “serious transgressions” of the Claimants’ representatives and the expert, the Court held that it had no confidence in Dr Gibson’s ability to act in accordance with his obligations as an expert witness. Permission for the Claimants to rely on Dr Gibson as an expert witness had been granted on the basis that he acted in accordance with his duties under CPR 35.3 and CPR PD 35 paragraphs 2.1 and 2.2 and the Court found that those duties had been undermined.

In these circumstances, despite Dr Gibson’s longstanding involvement in the claim and the significant costs spent on his advice (totalling £255,000), the Court found that it was “appropriate, and not disproportionate” to revoke the Claimants’ permission to rely on his evidence.

For these reasons, the Defendant was successful in its application and the Claimants’ permission to rely on Dr Gibson as a dust modelling expert was therefore revoked, leaving the Claimants needing to obtain alternative expert evidence.

Our comments

The decision serves as a useful reminder regarding the obligations of an expert witness – and for a party not to get too close to the expert so that the expert’s impartiality can be challenged. The expert’s overriding duty is to help the court on matters within their expertise; not to act as an advocate for the instructing party.

Expert witnesses and legal representatives must ensure that all communications comply with CPR Part 35 and communication between expert witnesses and representatives during the joint statement process should only occur in exceptional circumstances. Any such communications should be transparent.

The decision demonstrates that where the Rules are not complied with, the Court will apply the appropriate sanctions and whilst the Claimants in this case were granted permission to rely on a newly appointed expert, the cost ramifications will be significant. In addition the need to obtain fresh expert evidence means that the case will be delayed by a significant period of time.

For further information, please get in touch with Melissa Munday.

Please note that this briefing is designed to be informative, not advisory and represents our understanding of English law and practice as at the date indicated. We would always recommend that you should seek specific guidance on any particular legal issue.

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