Former Volkswagen CEO Martin Winterkorn went on trial Tuesday for his role in the "dieselgate" scandal, nine years after the saga first plunged the German auto titan into crisis.

VW admitted in 2015 that it had installed software to rig emissions levels in millions of vehicles worldwide, setting off one of Germany's biggest post-war industrial scandals.

Winterkorn faces charges including fraud over the use of the so-called defeat devices, which made cars appear less polluting in lab tests than they were on the road, and could be jailed for up to 10 years if convicted. 

He resigned as head of the VW group -- whose brands range from Porsche and Audi to Skoda and Seat -- shortly after the crisis began but attempts to bring him to trial had so far failed. 

Now 77, he was supposed to stand trial in 2021 alongside four other VW executives but proceedings against him were split off and postponed due to his poor health. 

Upon arrival at the regional court in the city of Braunschweig, close to VW's historic Wolfsburg headquarters, Winterkorn told reporters he was doing "quite well".

Asked how he looked back on his life's work, Winterkorn replied: "When I see the beautiful cars, very fondly."

He briefly addressed the court at the start of the hearing to confirm his personal details, speaking slowly and leaning on a chair for support.

Questions about Winterkorn's health hang over the proceedings, with reports saying he had to undergo an operation in mid-June. 

Some 89 hearings have been scheduled through September 2025.

Buyers 'deceived'

Winterkorn faces several charges. 

He has been accused of conspiracy to commit fraud, with the allegation based on the claim that buyers of some of the group's vehicles were "deceived about their characteristics" due to the use of defeat devices, according to the court. 

The alleged fraud relates to about nine million vehicles sold in Europe and United States, with the buyers facing financial losses running into hundreds of millions of euros, it said.

However, Winterkorn has not been accused of involvement in the offence for its entire period, which was from 2006 to 2015. He was VW chief executive from 2007 until 2015.

He has also been accused of giving false testimony to a German parliamentary committee in 2017 when it was investigating the scandal.

He said that he knew of the existence of the defeat devices only in September 2015 but prosecutors claim it was earlier.

Winterkorn further faces a charge of market manipulation.

He is alleged to have "deliberately failed to inform the capital market in good time" after finding out about the emissions-rigging software, in violation of German stock market regulations.

Winterkorn had already agreed a settlement with Volkswagen in 2021, under which he would pay the company 11 million euros ($12 million) in relation to the controversy.

Ahead of the trial, Volkswagen noted it was not party to the proceedings although it said that it would be monitoring them.

The highest-ranking former executive to have been convicted so far in the scandal is ex-Audi CEO Rupert Stadler.

In June last year, he received a suspended sentence and a fine as part of a deal in exchange for admitting to fraud by negligence.

The fraud has already cost VW more than 30 billion euros in fines, legal costs and compensation to car owners, mainly in the United States.