Authoritarians don’t have to be good liars—in fact, being bad at lying may be an advantage, since making one’s followers pretend to believe an obvious falsehood serves as both a show of strength and an easy loyalty test. Maybe that’s why Jeff Sessions did such a terrible job of lying at his Senate testimony, or maybe it’s just a skill he’s never had to cultivate. But whatever Sessions’ reasons, as Conan O’Brien noticed on Tuesday night, the embattled attorney general has a nervous habit that reliably indicates when he’s stretching the truth.

It’s subtle, but it’s there, and once O’Brien points it out, it’s impossible to ignore. Study the video carefully, and you might even be able to tell yourself the next time you see Jeff Sessions stretching the truth. Just don’t try to use the information to beat him in a poker game; he’ll probably arrest you for gambling.