They'll depart or cease responding. They'll disappear to avoid having to lie. They avoid conflict since they can't settle down once angry.
They repeat. Their story remains unchanged. Because they rehearsed it before talking to you, they use the same words every time.
Overcompensating, they stare at you and blink less. to appear unhidden. They overstate their truthfulness.
No eye contact. They fumble with jewelry or sleeves. Due to nervousness, they will stutter.
They'll say you're insane for fretting about whatever. They will mock everything. They'll humiliate you for doubting them.
They'll ignore you. When confronted about their lies, they change the subject. They'll try to avoid you until you stop asking questions.
They'll dispute. You'll anger them by saying they're lying. They'll use your past actions to excuse theirs this week.