The details just dont add up at all!
He/she gets super defensive!
He/she makes the lie seem like no big deal.
He/she tries to blame you for the actions shown!
He/she not making eye contact and hes turning away from you.
His/her body language is 'off'.
He is contradicting himself.
They keep avoiding the question.
They insist they 'do not lie'.
They repeat the questions you asked them.