Principles are ways of successfully dealing with reality to get what you want out of life.
Ray Dalio, one of the world’s most successful investors and entrepreneurs, cites principles as his key to success.
Investigate and explain to people that you are going to investigate so there are no surprises. Security controls should not be taken personally by the people being checked, just like a teller shouldn't view the bank counting the money in the drawer (rather than just accepting the teller's count) as an indication that the bank thinks the teller is dishonest. Explain that concept to employees so that they understand it.
But even the best controls will never be foolproof. For that reason (among many others), trustworthiness is a quality that should be appreciated.