Presumption of culpable mental state shifts burden, requiring an accused to prove absence of intent beyond reasonable doubt. The court shall presume the existence of a culpable mental state in prosecutions requiring such an element, but the accused may defend by proving absence of that mental state; 'culpable mental state' includes intention, motive, knowledge, and belief or reason to believe, and a fact is proved only when believed to exist beyond reasonable doubt rather than by a preponderance of probability.