The liar would probably avoid eye contact.

The liar would get anxious and play with her dress or hair or even sweat.

The liar would repeat the question to think of a response.

The liar would become happy after lying as if succesced.

The liar would probably leak their true emotions.

A liar would alter their voice tone.

A liar would try to escape the conversation.

A liar would add a lot of details about something.

A liar would struggle when trying to tell the same story again.