Various Claimants v Mercedes-Benz Group and Others [2026] EWHC 1753 (KB)

 

Summary

The trial dealt with liability issues relating to the alleged use of prohibited defeat devices. That is, devices which reduce the effectiveness of a vehicle’s emission control system for which there is no excuse or applicable exception. The judge criticised three of the expert witnesses for not complying with their duties under Part 35, and praised others.

Learning points

Learning points for instructing parties

• You will probably need to provide more support on the applicable rules and regulations, when you instruct an expert who does not usually act in the jurisdiction.

• Check expert reports for unintended content (such as notes or comments) before submitting them to the court.

Learning points for experts

• If you are acting in a jurisdiction where you do not usually act, make sure you fully understand, and comply with, applicable rules and regulations.

• If you have previously given evidence in similar cases, be aware that the opposing counsel may ask you to explain any inconsistencies with this previous evidence.

• Be careful not to provide opinions on matters outside your expertise. Always defer to experts in other fields if they have been instructed in the case.  

• Always accept and comply with the rulings of the court.

• Be wary of developing emotional attachments to the issues in the case, as they may influence your independence as an expert.

• Be careful not to rely inappropriately on your “team”.

• Ensure that you have removed any notes, comments, or tracked changes before submitting your report.

• If you are providing evidence in a language in which you are not entirely proficient, consider seeking the assistance of a translator. Even advanced language skills may fall short in the face of a lengthy, technical cross-examination.

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