Whenever performing Body Language Analysis, it's imperative that medical etiologies are not mistaken for Nonverbal causes.
In above video segment Senator John McCain is discussing Vladimir Putin and Russia's interference in the United States electoral process.
You may notice the left side of Senator McCain's face is moderately hypo-reactive relative to his right side (this image was captured during 0:58). This is most noticeable when comparing the right vs. left forehead as well as when contrasting the dynamics of the corners of McCain's mouth. This facial asymmetry is caused by a medical condition - a "Peripheral Facial Nerve Palsy" - which, in McCain's case is longstanding (one common sub-type of this condition is known as "Bell's Palsy").
Many nonverbal novices may (very falsely) interpret those with facial nerve palsies as projecting (and thus feeling) the emotion of contempt. That's not to say that individuals who are suffering from facial nerve palsies don't occasionally feel contempt - of course they do. But sussing out the distinctions between medical causes and nonverbal behavior is profoundly important. Knowing these details can make all the difference in the World.
Nonverbal Communication Analysis No. 3789: Felicity Jones, Jyn Erso and Tattoos
Nonverbal Communication Analysis No. 3787: Meghan Markle's Body Language - and some Ramifications for Prince Harry
Nonverbal Communication Analysis No. 3785: Hailee Steinfeld and Woody Harrelson "Edge of Seventeen" - Behavioral Contagions, Mirroring and Laughing
Nonverbal Communication Analysis No. 3769: Fidel Castro and Nikita Khrushchev
Nonverbal Communication Analysis No. 3664: Benjamin Netanyahu, Viktor Yanukovych and Vladimir Putin
Nonverbal Communication Analysis No. 3657: Abbey D'Agnostino, Nikki Hamblin and the Olympic Spirit
Nonverbal Communication Analysis No. 3563: Ariana Grande, Lip Stick, Microexpressions and Body Language
Nonverbal Communication Analysis No. 3642: Does Donald Trump Know Vladimir Putin?