The lawsuit against the fallen Volkswagen CEO Martin Winterkorn started on Thursday in the court of Braunschweig (Germany).
The court will investigate the role of the now 73-year-old Winterkorn in the diesel scandal to determine whether he can be found guilty.
The court, which earlier this month decided to prosecute, will, among other things, investigate whether Volkswagen should have notified shareholders earlier of possible fines.
The diesel scandal, in which cheating software was used to make engines appear cleaner than in reality, has cost the company more than 30 billion euros so far.
Volkswagen itself claims that the amount of the fines could not be foreseen.
When the diesel scandal came to light in 2015, Winterkorn was soon killed, despite his defense that he was unaware of the illegal practices. The former CEO's lawyer states that his client cannot be blamed for anything.