STUTTGART (Reuters) - Former Volkswagen (VW) Chief Executive Martin Winterkorn and Bosch [ROBG.UL] CEO Volkmar Denner are no longer expected to testify in a trial brought against VW's <VOWG_p.DE> main shareholder Porsche SE by investors, according to a judge.
Most of the two dozen witnesses called in the case have invoked their right to refuse to give evidence, Judge Fabian Richter Reuschle said in the opening of the trial in a regional court in Stuttgart.
"We have to accept that we cannot force them to incriminate themselves," Richter Reuschle said, adding the trial dates set aside for witness testimony through mid-November had been cancelled.
Shareholders represented by law firm TILP are seeking compensation from Porsche SE <PSHG_p.DE>, alleging the company did not inform markets quickly enough about the scale of potential liabilities VW faced over its use of illegal software to cheat U.S. emissions tests, disclosed in September 2015.
The start of proceedings in Stuttgart comes two days after a separate investor suit launched in the northern German city of Braunschweig, in which the plaintiffs are seeking billions of euros in damages from VW itself as well as from Porsche SE.
VW has admitted to cheating diesel emissions tests, but denies it failed to inform investors in a timely fashion. Bosch supplied key parts for VW's diesel engines, but says the integration of them was the responsibility of the manufacturer.
Had investors known about VW’s unlawful activities in rigging emissions tests, they may have sold shares earlier or not made purchases, thereby avoiding losses on their holdings, the plaintiffs argue.
VW shares lost up to 37 percent of their value in the days after authorities exposed illegal levels of pollution emitted from VW diesel cars.
A higher court in Stuttgart is due to rule on whether the suit against Porsche SE should be suspended to await the outcome of the Braunschweig trial, since the two cases are similar.
Porsche SE, the holding company of the Porsche and Piech families, owns about 52 percent of voting rights in VW. It is being sued by investors for a total of 865 million euros ($1 billion) in the two courts.
Porsche SE sees all of the suits as unfounded and in some cases without legal basis.
Like VW's management board, the board of Porsche SE had no knowledge of any cheating on diesel emissions tests before the matter became public in a "notice of violation" by the U.S. Environmental Protection Agency (EPA) on Sept. 18, 2015, the company says.
Winterkorn was the CEO of both Volkswagen and Porsche SE at the time.
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(Reporting by Ilona Wissenbach; Writing by Maria Sheahan, Editing by Tassilo Hummel and Mark Potter)