What do people mean when they say ';I can tell your lying when your lips move';?

I have heard this saying before. Is it some kind of tell? Or are they being sarcastic and saying that every time you open your mouth you lie?What do people mean when they say ';I can tell your lying when your lips move';?
usually its said sarcastically, meaning that you do nothing but lie when you talk.What do people mean when they say ';I can tell your lying when your lips move';?
sarcasm. every time you open your mouth, you are lying.
they are saying that every time you open your mouth you lie.
every time you open your mouth you lie
yes they are saying that everytime you speak you're telling a lie.
A person who says ';I can tell your lying when your lips move'; is saying ';I am unfamiliar with English grammar.';





The correct phrase is ';I can tell you're lying when your lips move';
When my ex used to lie his top lip would curl up, almost in a small smile.
It's the latter. Every time you open your mouth it's a lie.
It means they think he is a Democrat of course.