Daniel Carder said he's surprised to see such a hullabaloo now, because his team's findings were made public nearly a year and a half ago.
Volkswagen AG will probably have to show there was some legitimate reason to install software that led to false vehicle emissions tests.
In the day following Russian tennis star Maria Sharapova's admission that she failed a drug test, sponsors Nike, Porsche and Swiss watchmaker Tag Heuer dropped her like a hot potato.
The cars, some 482,000 Passats, Golfs and Jettas sold in model years 2009 to 2015 in the United States, are peppy and fun to drive, owners say.
Volkswagen AG said a scandal over falsified US. vehicle emission tests could affect 11 million of its cars around the globe.
Late on Monday, Volkswagen's U.S. chief Michael Horn said the company had "totally screwed up" and promised to make amends.