One nonverbal sign which is rarely discussed is the "Jaw Confessional". Although not as short-lived as a microexpression, it's a quite brief sideways (lateral) movement of the jaw (and may often have a lip component as well) which is indicative of some level of embarrassment as well as a "Hesitancy to Disclose".
There is very often a verbal confession or apology occurring just after a jaw confessional. Yet when nothing is said aloud - or when there is not an apology or confession - you can be very sure these thought-emotions are present (and thus a hesitancy to disclose and possibly a motive of deception). Whenever there's a disparity between what the spoken language and the body language are saying - it's the body language which always tells the truth. The jaw confessional is a profoundly valuable nonverbal tell in the courtroom, during a negotiation, an interrogation or in the sales process.
Be careful to differentiate this from a similar but slower and longer duration lateral jaw movement - for while it simply looks like a slow-mo variety of a jaw confession - it represents a completely different thought-emotion (Do you know what this other, slower and longer version means?).
In his recent appearance on Jimmy Kimmel Live, Samuel L. Jackson has a hesitancy to tell the audience just how big Magic Johnson's Yacht really is. He's embarrassed that many people will feel his friend's 180 meter long yacht (590 feet) is ostentatious and pretentious (and they'd very be correct). His jaw confessional is clearly seen during 1:06 (image captured below).
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