(Portuguese) Justice sucks!

why accused people don't have to say the truth (only whitnesses have to swear)?why accused people may listen to injured ones, but not the opposite?why judges and advocates do not think?can´t they tell by someone's eyes when he's lying? can i see something they can´t? Is the whole world so stupid as it seems?SO if I kill someone but nobody sees and there are no evidences, even if everything points at me, i get away with it. nice! Worst than justice, only cops.