The controversy came to public attention last week after Volkswagen acknowledged it had deliberately deceived officials about how much its diesel cars polluted.
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.
Industry experts said the scandal could hit VW hard, just as it was emerging from a damaging leadership battle.
Late on Monday, Volkswagen's U.S. chief Michael Horn said the company had "totally screwed up" and promised to make amends.