LONDON: Some of the world’s biggest carmakers largely won the first stage of a major legal battle on Friday over claims that their diesel vehicles were fitted with unlawful “defeat devices” that led to higher emissions.

In a summary of her judgement, Judge Sara Cockerill said she had “rejected most of the principal allegations advanced against the manufacturers whose vehicles were examined at trial”.

She said that a defeat device under emissions regulations only covered “devices which operate with the intentional and/or impermissible purpose of causing the (emissions control system) to operate differently when it senses the test cycle”.

The case at London’s High Court centred on 20 sample vehicles made by Mercedes-Benz, Ford, Nissan , Renault and the Stellantis-owned brands Peugeot and Citroen.

Cockerill made some findings against the carmakers, including over a coolant temperature device used in some Mercedes cars that was removed in a Dec 2015 update and which she said did not reduce the effectiveness of the emissions control system.

The judge also made an adverse finding in relation to a combustion mode used in some Peugeot-Citroen vehicles.

A Mercedes-Benz spokesperson welcomed the ruling, saying the court had found “very largely in favour” of the company. The automaker said it disagreed with the finding against it and was considering its options, including a possible appeal.

Stellantis said only one allegation was upheld against it and it was considering the possibility of seeking leave to appeal.

“Stellantis maintains its firm position that all its vehicles comply with applicable emissions regulations,” the manufacturer said in a statement.

Lawyers representing the claimants said they were considering a possible appeal against Friday’s ruling, which they said “adopted a significantly narrower interpretation of the law than that applied elsewhere in Europe”.

Published in Dawn, July 11th, 2026