Former Audi boss Rupert Stadler has become the first top executive to stand trial over Germany’s dieselgate scandal, which rocked the auto industry in 2015.
Mr Stadler appeared in a Munich court on Wednesday on fraud charges, which he denies.
Audi owner Volkswagen has admitted to installing software that cheated emissions tests in 11 million diesel vehicles around the world five years ago.
Not a single top leader has been convicted of the scandal in Germany.
However, two VW employees were sentenced to prison terms in the United States.
Mr Stadler is accused of knowingly selling cars that manipulated engine software and did not meet environmental standards.
When US regulators discovered the scam in 2015, VW first claimed that it was the work of a handful of engineers and that no senior executives were involved.
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But employee testimony led prosecutors to take Mr. Stadler into custody for four months in 2018.
Former Audi and Porsche director Wolfgang Hatz and two former engineers, who also deny the fraud charges, are also in attendance.
The defendants face charges relating to more than 434,000 VW, Audi and Porsche vehicles sold in Europe and the United States. If found guilty, they face up to 10 years in prison, although a decision is not expected until December 2022.
Mr Stadler is not the only one facing high-level judgment. Former VW group boss Martin Winterkorn will also be on trial for fraud and stock market manipulation.
Current VW boss Herbert Diess and board chairman Hans Dieter Poetsch faced similar allegations, but those proceedings were dropped after VW agreed to a € 9million settlement.
The “dieselgate” scandal has already cost VW more than 30 billion euros in fines, legal costs and compensation for car owners, mainly in the United States.
Rivals Daimler and Fiat Chrysler have also since faced emissions rigging charges.
In April, VW settled the biggest lawsuit in Germany – agreeing to pay around € 750 million to 235,000 customers with affected cars.
He is now trying to come to an agreement with 60,000 other plaintiffs who want the automaker to buy back its diesel vehicles.