Let's assume there's no documentation or non-conspiring witnesses who can pin someone, but there are five co-conspirators. They will quickly turn on each other and spill the beans. Literally the prisoner's dilemma. All the government needs to do is threaten 20 years in prison. People will do anything including betraying friends and lovers to get that down to 5 or 10 or zero.
I would suggest that a CEO should know where any magic beans are coming from beyond a reasonable doubt. Not knowing where those magic beans are coming from is its own kind of special trouble, from a legal liability perspective.