Former Volkswagen CEO, Martin Winterkorn, and Bosch CEO, Volkmar Denner, are among witnesses refusing to testify in a trial against Porsche SE, the main shareholder of Volkswagen Group.
The presiding judge of the regional court in Stuttgart, Fabian Richter Reuschle, said of the decision: “we have to accept that we cannot force them to incriminate themselves," according to reporting from Automotive News.
The lawsuit relates to allegations Porsche SE took too long to inform investors of the scale of liabilities faced over its use of illegal software to cheat emissions tests in the USA.
While Porsche SE have admitted to cheating the emissions tests, it denies claims that it failed to inform its investors in a timely manner.
The plaintiffs claim had they known about the illegal activities, they would have either sold or not bought shares in Porsche SE, which lost 37 per cent of its value in the days after the allegations were made public.
Both the board of Porsche SE, as well as Volkswagen's management board claim that they had no knowledge of the violation until the US Environmental Protection Agency made the matter public in September of 2015.
Porsche SE is also being sued by investors in its home state of Lower Saxony.
Between the two cases, Porsche SE is potentially liable for up to $1.4 billion in damages.