I think the way people act influences the way their appearance is perceived in very subtle ways. A sketchy liar could have exactly the same bone structure as an honest man, but the sketchy liar will be perceived as less honest due to almost imperceptible differences in body language, the way they hold their facial muscles, etc. The result of these subtle differences can be detected with a vague sensation of "this guy is sketchy, he's probably about to lie to me."

Also I think there is an element of truth to the old wive's tail of "your face is going to get stuck like that". People who frequently have malicious facial expressions in private will find themselves having malicious facial expressions when they don't mean to, when interacting with the people they intend to deceive. Maybe out of pure habit, or maybe because those muscles are just getting more exercise. Somebody who often has a lopsided smirk will develop muscles on one side of their face more than the other, and eventually they can't help but to smirk by default.