Lawyers aim to appeal Dieselgate ruling

Lawyers representing 1.6 million motorists implicated in the Dieselgate scandal are preparing to seek permission to appeal a trial judgment made earlier this year. The High Court will hear their application on 7-8 October 2026, as they contest a ruling from a 13-week trial that concluded on 10 July. The court found that only three out of twenty representative vehicles examined had breached emissions regulations. Specifically, one Mercedes and two Peugeot/Citroen models were determined to have contained so-called Prohibited Defeat Devices (PDDs), which are engineered to reduce emissions output during testing conditions rather than under real-world driving scenarios.

In stark contrast, the remaining 17 vehicles, produced by manufacturers including Ford, Renault, and Nissan, were cleared of any wrongdoing. The judgment has raised concerns about the legal stance in England and Wales, diverging sharply from much of Europe following the Brexit decision not to align with several critical CJEU rulings. As a result, defeat devices deemed unlawful in the EU may still be permissible in England and Wales, according to legal experts.

The claimants’ legal team intends to challenge the judgment on several grounds. First, they argue that the judge adopted an overly narrow definition of a PDD, focusing solely on specific test-recognition devices, akin to those found in Volkswagen vehicles implicated in past emissions test scandals. They also contend that the ruling is inconsistent with established CJEU authorities, thus placing England and Wales in a distinctly unfavourable position with respect to defeat device regulation.

Martyn Day, senior partner at Leigh Day, commented on the appeal, stating, “Our appeal will argue that the judge applied too narrow a definition of what constitutes a Prohibited Defeat Device and that some of the technical evidence around this issue should be looked at again.” Day further emphasised the importance of the appeal, remarking that despite manufacturers denying wrongdoing, the judge acknowledged unlawful defeat devices in Mercedes and Peugeot/Citroen models. He concluded by stressing the critical nature of addressing the divergent legal landscape that risks leaving England and Wales as the only jurisdictions permitting such devices.