Presumption of culpable mental state shifts the burden yet permits accused to prove absence of the mental element beyond reasonable doubt. The Act presumes the existence of any required culpable mental state in prosecutions, while allowing it as a defence for the accused to prove absence of that mental state regarding the charged act. 'Culpable mental state' is defined to include intention, motive, knowledge, and belief or reason to believe. The provision further prescribes that a fact is proved only when the court believes it to exist beyond reasonable doubt and not by mere preponderance of probability.