So far, six men have been formally charged, accused of defrauding the United States and Volkswagen customers there, of violating the Clean Air Act and of committing wire fraud. A seventh has pleaded guilty to conspiring to defraud regulators and car owners.
And more charges could be in the offing. The Obama administration is not only hitting at charges that it has been soft on white-collar crime, but also hopes the latest allegations could lead to more action against higher-level executives.
“Volkswagen deeply regrets the behavior that gave rise to the diesel crisis. Since all of this came to light, we have worked tirelessly to make things right for our affected customers,” Matthias Müller, chief executive of Volkswagen, has said. “The agreements that we have reached with the U.S. government reflect our determination to address misconduct that went against all of the values Volkswagen holds so dear. They are an important step forward for our company and all our employees.”
None of the executives charged have responded to requests for comment.
Here are the people who have been charged so far:
Heinz-Jakob Neusser, 56, executive showman
By far the most prominent person indicted so far, Mr. Neusser was one of the select few executives who presented new models at car shows. Before his resignation in 2015, he oversaw 10,000 people at Volkswagen’s vast development complex in Wolfsburg, Germany, which has its own test track. Mr. Neusser was known inside Volkswagen for his loyalty to Martin Winterkorn, Volkswagen’s chief executive until he resigned when the scandal broke.
Mr. Neusser took over responsibility for developing new engines for Volkswagen brand cars in 2011, after the illegal software had already been deployed in millions of cars around the world. But, according to prosecutors, he played a major role in refining the software and concealing its existence from regulators.
After engineers complained that the software was causing engine malfunctions, Mr. Neusser ordered changes that reduced pollution controls even further and told employees to destroy evidence, according to the indictment against him.
Jens Hadler, 50, engines expert
When Volkswagen decided to build a new diesel engine as part of an all-out drive to recapture past glory in the United States, the company tapped Mr. Hadler, who has a doctorate in engineering, to oversee the project known as “U.S. ’07.”
The pressure was intense. The United States was central to a grand plan by Volkswagen to become the largest carmaker in the world. But sometime in 2007, Mr. Hadler and others realized that the company lacked the technology needed to meet tougher American emissions standards, according to the indictment. That is when Volkswagen resorted to the use of a “defeat device,” making engines seem cleaner than they actually were.
Unlike several other suspects, Mr. Hadler is not accused of participating in a cover-up. He left Volkswagen in 2011 and was replaced by Mr. Neusser.
Richard Dorenkamp, 68, emissions specialist
Mr. Dorenkamp, who specialized in emissions systems, was crucial to the development of the new diesel engine for the American market. Like several other suspects, he was well-known in industry circles, speaking at universities and conferences, and writing articles in technical journals. Mr. Dorenkamp’s name is on numerous patents related to engine technology.
When it became clear that the new diesel engine couldn’t meet emissions standards legally, Mr. Dorenkamp played a key role in the conspiracy to develop illegal software, according to prosecutors. He retired in 2013.
Bernd Gottweis, 69, troubleshooter
Mr. Gottweis was a quality-control executive known as “the fireman” for his troubleshooting skills. When a defect turned up in Volkswagen vehicles somewhere in the world — a common occurrence in the industry — he was often one of the first on the scene.
A memo he wrote in May 2014 has become a key piece of evidence in the case, suggesting that top levels of management learned of illegal software much sooner than Volkswagen has admitted.
The memo, a one-page document that was included in federal court filings, warned that a study by a handful of researchers at West Virginia University had revealed strange behavior by Volkswagen diesel cars in the United States. Regulators might investigate whether Volkswagen was using a defeat device, and there was nothing Volkswagen could do to make the cars legal, the memo said.
The warning was put in a stack of weekend reading for Mr. Winterkorn. Volkswagen has said it is not certain that the chief executive read it, but it would have been unusual for Mr. Winterkorn to ignore a memo from someone of Mr. Gottweis’s stature.
Oliver Schmidt, 48, regulatory go-between
Mr. Schmidt was Volkswagen’s point person in dealing with American clean-air regulators, overseeing Volkswagen’s emissions compliance office in Michigan from 2012 until 2015. United States investigators accuse Mr. Schmidt of being in the middle of a campaign to deflect suspicion about Volkswagen cars by supplying reams of false or misleading data to clean-air enforcement agencies.
Even after returning to Volkswagen headquarters in early 2015 — where he worked for Mr. Neusser — Mr. Schmidt continued to try to keep United States regulators from discovering the defeat device, according to court documents.
Exposure of the defeat device in September 2015 did not initially appear to hurt Mr. Schmidt’s career, but he appears to have underestimated how much trouble he was in. Although he had already been questioned by United States investigators in Europe — an indication he was a target — Mr. Schmidt left the safety of Germany and traveled to Florida. F.B.I. agents took him into custody at Miami International Airport on Jan. 7 shortly before he was scheduled to board a plane back home. Judged a flight risk, he was being held without bail.
Jürgen Peter, 59, quality control
Mr. Peter, a longtime employee of a unit responsible for vehicle quality and safety, was less prominent than the other suspects. But, according to the indictment, he worked behind the scenes in Wolfsburg to concoct excuses for why Volkswagen vehicles polluted so much more on the road than in lab tests.
He is perhaps most famous as the source of a widely quoted expression of panic within Volkswagen as it became increasingly difficult to figure out ways to placate regulators. As California officials were intensifying tests of Volkswagen vehicles in mid-2015 and it appeared increasingly likely that the company would be exposed, Mr. Peter, it was said, wrote in an email to colleagues, “Come up with the story please.”
James Robert Liang, 62, software engineer
Mr. Liang is the only person so far to plead guilty in connection with the Volkswagen scandal, and has agreed to cooperate with prosecutors. He appears to have had a front-row seat to all that was happening inside the company as the scandal unfolded, making him a particularly valuable informant.
Having worked at Volkswagen since 1983, Mr. Liang was involved in designing the new diesel engine starting in 2006 and has admitted to being among the group of people who developed and refined the defeat device.
As Volkswagen began shipping cars with the new engine to the United States in 2008, according to Mr. Liang’s plea agreement, he moved to the country, where his duties included working with clean-air officials to get approval for the cars to go on sale. That meant lying about how Volkswagen was cheating on emissions tests.
Mr. Liang’s lawyer has described him as “very remorseful for what took place.” He is awaiting sentencing.