In other words, a person can tell the "truth" as the person perceives it, but the statement can actually be a false statement. For example, a witness of 9/11 may say that he saw meteors crash into the towers. A lie detector may show that witness is NOT being deceptive. However, that statement about meteors is false according to reliable evidence showing that it was not meteors that crashed into the towers.

A person's memory or perception is an unreliable indicator of what the truth actually is. The most convincing liar is the liar who is able to convince himself that he is telling the truth. I know two compulsive liars. They lie about almost everything, even if they don't have to lie. They lie so much that I believe they don't know when they are lying. Their skill is quite fascinating, at a distance that is.