Oliver Schmidt, a former high-ranking employee at Volkswagen, pleaded guilty Friday to charges that he led the company in its attempts to willfully violate U.S. air emissions rules.

Schmidt admitted guilt to four of the 11 charges leveled against him during a federal district court hearing in Detroit. He could serve up to seven years in prison and pay a $400,000 fine, according to District Court Judge Sean Cox.

Schmidt will go back to the court Dec. 6. for sentencing, and he agreed to be deported after he completes his sentence. He pleaded guilty to three conspiracy charges and one charge of violating the Clean Air Act.

Schmidt was the central figure in what is commonly referred to as the "dieselgate" scandal, in which the German automaker tried to thwart federal air emission rules by installing a defeat device in more than 500,000 diesel cars sold in the United States.

The device, which is computer software, turned off emission controls during driving, and switched them on when a vehicle sensed it was undergoing emission tests.

"Schmidt participated in a fraudulent VW scam that prioritized corporate sales at the expense of the honesty of emissions tests and trust of the American purchasers," said Deputy Assistant Attorney General Jean Williams in court Friday. "Schmidt, along with each and every official involved in this emissions scandal, will be held fully accountable for their actions by the Department of Justice as this investigation continues."

The scandal has cost the company $25 billion for the U.S. violations alone.