A man is praised according to his insight, but one with a twisted mind is despised.
Proverbs 12:8 TLV

With enough interaction, eventually most people can see a person for who he really is. Foolishness and wisdom, stupidity and intelligence, criminality and justice are all apparent in most people if you watch them long enough, which is why Solomon also said that even a fool is thought wise if he keeps silent. Even the best at hiding themselves can't hide from God.