Lucas123 writes: The method by which Volkswagen diesel cars were able to thwart emissions tests and spew up to 40X the nitrogen oxide levels set by the Environmental Protection Agency was relatively simple. It was more likely no more than a single line of code used to detect when an emissions test was being performed and place the emissions system in an alternate mode — something as simple as a software "on/off" switch. Volkswagen AG CEO Martin Winterkorn, who stepping down as the result of his company's scandal, has said he had no knowledge of the emissions cheat, but software dev/test audit trails are almost certain to pinpoint who embedded the code and who authorized it. You can actually see who asked the developer to write that code," said Nikhil Kaul, a product manager at test/dev software maker SmartBear Software. "Then if you go upstream you can see who that person's boss was...and see if testing happened...and, if testing didn't happen. So you can go from the bottom up to nail everyone."