Presumption of culpable mental state shifts proof burden to accused to establish absence of mens rea beyond reasonable doubt. The Act presumes that an accused possessed the requisite culpable mental state (including intention, motive, knowledge, and belief), but allows the accused a defence to prove absence of that mental state with respect to the charged act; facts are regarded as proved only when the court believes them to exist beyond reasonable doubt rather than by a preponderance of probability.