How a person can lie to someone who knows the truth already?

We should not tell a lie in any case. I will try to speak the truth in every situation. But I have seen a person in my life who is very steadfast in telling lie, he used to say that I lie with my feet tied. I lie and then stick to it, no matter how much evidence or proof someone has, they can't force me. For example, as he is working in WAPDA, he said that if my boss asks for the pressure of machine, I"ll tell him a figure without checking. If he investigates the pressure and it is different, still I"ll stick to my statement, and argue at that moment it was, what I told. He is behaving on the Persian proverb زمین جنبد نہ جنبد گل محمد, The earth can shake, but Gul Muhammad cannot leave his place.

It is not good if you have committed any mistake, admit it, and never commit it again. It will bring comfort, peace, and dignity in your life.