High Court Rejects Most Dieselgate Claims
High court rejects most of dieselgate – The High Court has rejected most of the dieselgate claims brought by 1.6 million UK car owners in a landmark legal battle. Motor manufacturers celebrated the decision, which largely dismissed accusations that their vehicles contained prohibited defeat devices. Lady Justice Cockerill ruled that “in the majority of instances, the court found that the relevant strategy did not constitute a prohibited defeat device” – software allowing engines to operate differently during official tests compared to real-world driving.
Understanding the Ruling
While the overall outcome favored car producers, the judge acknowledged that certain technologies in Mercedes-Benz and Peugeot-Citroën vehicles might indeed qualify as prohibited defeat mechanisms. Lawyers for the claimants are now considering whether to appeal, noting this decision creates a significant divergence between British law and that of many European countries.
Plaintiffs argued that automotive companies deliberately engineered vehicles with systems that lowered nitrogen oxide (NOx) emissions during laboratory testing relative to actual road conditions. Manufacturers countered that they never employed forbidden defeat devices. This case, the largest collective action trial in English legal history, ran through the High Court for fifteen weeks from October 2025 to March 2026.
“Not every calibration or emissions-control strategy amounts to a defeat device,” the judge observed during her proceedings.
Testing Difficulties and Scope
Lady Justice Cockerill stressed that proving deliberate intent to manipulate test results remained crucial for claimants. She clarified that “it was not enough for the claimants simply to establish that the challenged strategies reduced the effectiveness of emissions-control systems outside the relevant testing conditions.” Her assessment also noted that “testing, however, is difficult to interpret and none of the approaches to isolating the effect of a particular calibration on NOx was entirely satisfactory.”
The ruling further acknowledged that “if an alternative approach to the meaning of ‘defeat device’ were taken a larger number of defeat devices would be established, including devices in each of the lead manufacturers cars.” The proceedings focused on twenty vehicles from five producers – Mercedes, Ford, Renault, Nissan, and Peugeot/Citroën – dating from 2009, though the decision extends beyond these specific cases.
What Manufacturers Said
Mercedes-Benz described the outcome as ruling “very largely in favour” of their position while indicating they might still appeal regarding one vehicle classified as non-compliant. That particular functionality had already been removed from their fleet by 2015. Stellantis, which owns Peugeot-Citroën, similarly signaled potential appeal intentions concerning the allegations they failed to dismiss entirely.
Nissan maintained their consistent position that their vehicle technologies never represented prohibited devices, while Renault asserted their automobiles were “designed, engineered, and manufactured in accordance with all applicable regulatory requirements.” Ford received requests for additional commentary. All four responding companies publicly welcomed the judicial outcome.
“The high court has found that despite their denials, other manufacturers also used VW-style defeat devices,” explained Martyn Day, senior partner at Leigh Day.
Legal Teams and Future Outlook
This inaugural British legal determination emerged more than ten years after initial revelations that Volkswagen engines operated under distinct conditions during testing, thereby concealing genuine NOx pollution levels from the public. Over twenty legal practices initiated the proceedings, with Leigh Day and Pogust Goodhead serving as lead organizations.
Leigh Day characterized the verdict as “disappointing,” noting it permitted defeat devices that would likely face illegality across the European Union within Great Britain. Martyn Day added that the judge “surprisingly disagreed with the established EU case law on what a defeat device is,” allowing many additional mechanisms to remain lawful.
Anna Varga from Pogust Goodhead commented that the judgment “does not bring this litigation to an end,” highlighting both the complexity of the legal questions and the potential for further appeals as claimants weigh their options following this significant High Court decision on dieselgate claims.
