A criminal trial against ex-Volkswagen boss Martin Winterkorn over his alleged role in the company’s diesel emissions scandal has been scheduled to begin in September. The lengthy proceedings, which could last for more than a year, will combine multiple criminal complaints against the former Volkswagen chief executive. Winterkorn faces allegations of fraud, false statements and market manipulation in the scandal, which became public after regulators in the United States in 2015 discovered that software on Volkswagen diesel-powered vehicles intentionally manipulated their performance during emi…