Former Volkswagen Group chief executive Martin Winterkorn apparently knew of the company’s diesel cheating for at least 15 months before the scandal broke, his indictment says.

Automotive News reports that Winterkorn actively tried to cover up the company’s use of diesel cheat devices. The 70-year-old has been charged by a federal grand jury in Detroit with one count of conspiring to defraud the U.S. and three counts of wire fraud. Winterkorn quit as VW chief executive just days after the scandal emerged in September 2015.

Attorneys in the U.S. petitioned to unseal Winterkorn’s March 2018 indictment on Thursday. It asserts that he was specifically told about the cheating in May 2014. Additionally, he presided over a meeting in July 2015 where Oliver Schmidt was told to lie to regulators. This comes despite claims from the automaker that Winterkorn had no prior knowledge of the cheating.

The indictment also alleges that VW’s head of engine development after-treatment department, Richard Dorenkamp, oversaw the development of the defeat devices and that VW head of engine development Jens Hadler approved the use of the devices.

Despite being charged in the United States, Winterkorn may never face trial in the country as he cannot be extradited from his home country of Germany. If he is ever caught outside of Germany, he could be arrested and extradited.