A High Court judge has ruled that most major car manufacturers did not install prohibited defeat devices (PDDs) in their diesel vehicles, a decision that dismisses the majority of claims brought by around 1.6 million motorists. The group had alleged that diesel cars produced from 2009 onwards contained devices designed to cheat emissions tests.
The ruling by Lady Justice Cockerill followed a ten-week trial involving 20 sample vehicles from five manufacturers: Mercedes-Benz, Renault, Nissan, Ford, and Peugeot and Citroen. The motorists claimed they were misled about the emissions levels of their vehicles.
In a 369-page judgment, the court found that while one strategy in Mercedes cars and some in Peugeot-Citroën vehicles were deemed prohibited, most of the emissions control strategies examined did not constitute PDDs. The judge stated that for a defeat device to be found, there must be an intention for the emissions control system to operate differently when it detects testing conditions, and that it was not sufficient to merely show that challenged strategies reduced the effectiveness of emissions control systems outside of testing scenarios.
"The Court rejected most of the principal allegations advanced against the manufacturers whose vehicles were examined at trial," the judgment read. "In the majority of instances, the Court found that the relevant strategy did not constitute a prohibited defeat device."
Mercedes-Benz welcomed the ruling but indicated it disagreed with the court's finding that one of its four sampled vehicles was non-compliant before a software update. The German automaker stated it is considering its options, including a potential appeal.
Solicitors representing the claimants noted that the judge acknowledged that a different interpretation of 'defeat device' could lead to a larger number of devices being established, including in the lead manufacturers' cars. One firm representing claimants stated, "We are pleased that the court has ruled that Mercedes installed illegal defeat devices, just like Volkswagen. 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."
A further trial is scheduled for October to determine the consequences of any actionable breaches and address issues related to damages or other remedies.
The case examined a limited number of vehicles. The wider legal action also involves manufacturers such as Opel, Vauxhall, Volkswagen, Porsche, Jaguar Land Rover, BMW, FCA, Suzuki, Volvo, Hyundai-Kia, Toyota, and Mazda. The initial dieselgate scandal, which first came to light in September 2015, involved Volkswagen admitting to using defeat devices to circumvent emissions tests, leading to global fines and compensation payments. This scandal resulted in approximately 11 million cars worldwide being fitted with the software, with Volkswagen paying out around £27.8 billion globally, including £193 million to 91,000 British motorists.
Reports cited in the trial suggested that excess nitrogen oxide emissions from diesel engines have been linked to significant health issues, including premature deaths and new cases of asthma in children in the UK and Europe between 2009 and 2024.