Mien is a noun that means a person's appearance or manner.
Mien originated in Middle French, where it meant “appearance” or “facial expression.” As the word shifted to modern English, its spelling changed a little, but its definition is roughly the same. A person’s mien is basically a reference to their manner — physically and otherwise.
I could somehow tell that Andrew wasn’t guilty of the crimes he was accused of. There was something in his mien that suggested a man to innocent to have committed fraud.