Presumption of culpable mental state: accused may prove absence of mens rea, facts require beyond reasonable doubt. Presumption applies that a required culpable mental state existed in prosecutions under the Wealth Tax Act; the accused may defend by proving absence of that mental state. 'Culpable mental state' includes intention, motive, knowledge, or belief or reason to believe a fact. A fact is proved only when the court believes it to exist beyond reasonable doubt, not by a preponderance of probability.