Should あなた believe a chronic liar if he says he is a chronic liar?

That's too much of a contradiction there... もっと見る like, a chronic liar won't tell the truth, no matter what. So, therefore, he would never say he was a chronic liar in the first place, unless he really wasn't a liar.

I don't know.

Therefore, the following statement is true.
The 前 statement is false.