Missed Opportunity With Truth - Possible Plot Hole/Goof
It is established that he cannot tell a lie regardless of if he has actual knowledge in regards, case, and point, the "I have to pee" scene in court. The judge asks, "can it wait?" and he replies "yes, it can", but follows up with "But holding it in can make it difficult to pee or even get an erection". The judge asks "Is that true?" to which he responds, ""It has to be".
That means he can only speak universal truths, not just things that are true as far as he is concerned.
That means he can find out all the world's mysteries.
E.g. He could attempt to say "Aliens have been visiting earth for..." and if he can say it then it must be true.