Explain "facecrime" and give an example

Facecrime is the unknowing act of revealing your thoughts or emotions to someone else. An example of this can be found when Winston worries that the dark-haired girl in the office has been watching him.

He did not know how long she had been looking at him, but perhaps for as much as five minutes, and it was possible that his features had not been perfectly under control. It was terribly dangerous to let your thoughts wander when you were in any public place or within range of a telescreen. The smallest thing could give you away. A nervous tic, an unconscious look of anxiety, a habit of muttering to yourself -- anything that carried with it the suggestion of abnormality, of having something to hide. In any case, to wear an improper expression on your face (to look incredulous when a victory was announced, for example) was itself a punishable offence. There was even a word for it in Newspeak: facecrime, it was called.

A facecrime is a facial expression that betrays an emotion that is considered incorrect or undesirable by the ruling authority. For example, on September 8, 2018, Tyler Linfesty, a 17 year old high school student who would become known as "plaid shirt guy" was removed from a Donald Trump's campaign rally and questioned for 10 minutes by secret service agents after displaying inappropriate facial expressions in response to Trump's comments.