When expert witnesses fail: The Marples Judgment and its costly consequences

Nichola Evans, Partner

Clients often assume that appointing an expert witness will strengthen their case and improve their chances of success. However, this is not always true. The recent judgment in Marples serves as a timely reminder of the strict obligations placed upon expert witnesses and highlights that their primary duty is to the court, not to those instructing them.

The Facts

The claimants, Mr Marples, his wife Sarah, his son Thomas, and his nephew Lee brought a claim against the defendant, the Secretary of State for Education.

In preparation for the trial, both parties instructed experts to provide forensic accountancy evidence. The claimants instructed Mr Cohen to prepare an expert report.

Mr Marples was a trained accountant, and it transpired that Mr Marples had been in regular and free flowing communication with Mr Cohen without the knowledge of the claimants’ solicitors. Mr Marples and Mr Cohen had prepared and drafted a joint statement together which had 150 amendments made by Mr Marples.

Accordingly, the defendant made an application to revoke permission for the claimants to rely on their expert evidence.

The Judgment

The Judge first pointed to the obligations which are owed by experts set out in the Rules – their duty is to help the court on matters within their expertise and this duty overrides any obligation to persons who pay or instruct them.

Upon reviewing the correspondence between Mr Marples and Mr Cohen, the Judge found that:

1. There was a deliberate, cynical, planned breach of the rules relating to the preparation of expert evidence;
2. Mr Cohen’s report and the joint report were not independent. They did not represent Mr Cohen’s objective and unbiased opinion;
3. The Judge had no confidence in Mr Cohen’s ability to act in accordance with his obligations as an expert witness. Key messages from the case:

• An expert witnesses’ duty is owed to the court, not clients. It is extremely important for clients to refrain from having too much input on expert witnesses. Failure to remember this may result in sanctions which disallow clients relying on their own expert’s reports.
• Client correspondence with experts (especially where the client is an expert in that field) should be at least monitored by solicitors. This will ensure that the expert’s duty to the court is maintained and client’s funds are not wasted on unusable experts.

This judgment follows the court’s strict approach to expert evidence. For example, the recent Kronospan case confirmed that the court will critically assess expert findings which change materially from their first findings. This is because the courts are focusing on whether experts have maintained their obligations to the court, rather than their clients.

The dispute resolution team at Kuits can assist you in navigating challenges with maintaining impartiality when instructing expert witnesses.

For more information on this or any other topic please do not hesitate to contact our team on 0161 832 3434 or via email info@kuits.com.

Marples v Secretary of State for Education [2025] EWHC 2794 (Ch)

Patricia Andrews & Ors v Kronospan Limited [2025] EWHC 2429 (TCC)

Contributors, Reuben Nesarajah, Trainee Solicitor