A High Court judge has ruled that vehicles from Renault, Nissan, Ford and most Mercedes and Peugeot-Citroën models did not contain illegal emissions-cheating devices, in a landmark judgment affecting a lawsuit brought by 1.6 million UK motorists, though claimants say the ruling still identifies unlawful software in specific Mercedes and Peugeot-Citroën vehicles.
A High Court judge has largely cleared five major car manufacturers of installing illegal emissions-cheating technology, in a ruling that forms part of one of the largest group legal actions in UK history. Lady Justice Cockerill handed down her 369-page judgment following a ten-week trial examining 20 sample diesel vehicles from Mercedes-Benz, Renault, Nissan, Ford, and Peugeot and Citroën, concluding that most of the strategies used in these vehicles did not amount to “prohibited defeat devices.” The exceptions were one software function found in certain Mercedes vehicles, which was removed in 2015, and another identified in some Peugeot-Citroën models.
What the Court Found
Around 1.6 million motorists, most based in England and Wales, are pursuing claims against more than a dozen manufacturers over allegations that diesel vehicles produced from 2009 onwards contained devices designed to detect emissions testing and reduce harmful output accordingly, before reverting to higher-polluting settings during normal driving. Barristers for the claimants argued this amounted to systematic deception about the vehicles’ true environmental performance.
The court rejected the majority of these claims. “The Court rejected most of the principal allegations advanced against the manufacturers whose vehicles were examined at trial,” the ruling stated, adding: “In the majority of instances, the Court found that the relevant strategy did not constitute a prohibited defeat device.” Lady Justice Cockerill set out a clear legal threshold for what constitutes such a device, ruling that “for a defeat device to be found, there needs to be an intention to cause the emissions control system to operate differently when it senses it is being tested,” and 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.”
However, claimants’ solicitors highlighted a significant caveat in the judgment: Cockerill noted that “if an alternative approach to the meaning of ‘defeat device’ were taken, a larger number of devices would be established, including devices in each of the lead manufacturers cars.”
Reaction From Manufacturers and Claimants
Mercedes broadly welcomed the ruling but pushed back against the finding relating to one of its four sample vehicles, which the court found had not been compliant prior to a software update. The German manufacturer said: “In our view, the emission control software functionalities are justifiable on both technical and legal grounds. We are actively considering all of our available options, including a potential appeal.” Peugeot-Citroën had not issued a response at the time of the ruling.
James Oldnall, managing partner at Milberg, which represents some of the claimants, struck a defiant note despite the largely favourable outcome for manufacturers. “We are pleased that the court has ruled that Mercedes installed illegal defeat devices, just like Volkswagen,” he said. “The fight is not over on this case, but the first domino has fallen. We are on the right path and will continue pushing to hold these carmakers to account.”
What Happens Next
The ruling covers only the 20 sample vehicles examined from the five manufacturers involved in this stage of the litigation. The wider legal action also encompasses vehicles made by Opel and Vauxhall, Volkswagen and Porsche, Jaguar Land Rover, BMW, FCA and Suzuki, Volvo, Hyundai-Kia, Toyota and Mazda. A further High Court trial is scheduled for October this year, which will address the consequences of any confirmed breaches, along with questions of damages and other potential remedies for successful claimants.
The Wider Dieselgate Legacy
The case forms part of the fallout from the “Dieselgate” scandal, which first emerged in September 2015 when the US Environmental Protection Agency accused Volkswagen of fitting software to diesel vehicles that could detect official emissions testing and temporarily reduce nitrogen oxide output, before switching off these controls during ordinary driving to improve performance. Volkswagen later admitted the devices had been deliberately installed to circumvent US emissions testing, and had been fitted to approximately 11 million vehicles worldwide. The company has since paid out around £27.8 billion globally in fines and compensation, the majority in the United States, including £193 million paid to 91,000 British motorists.
During the London trial, barristers representing the car owners cited research from the Centre for Research on Energy and Clean Air, which found that excess nitrogen oxide emissions from diesel engines had contributed to 124,000 premature deaths and 98,000 new cases of childhood asthma across the UK and Europe between 2009 and 2024.
