Presumption of culpable mental state creates a rebuttable presumption requiring accused to prove absence of mens rea. Section 135 creates a rebuttable statutory presumption that a required culpable mental state exists in prosecutions under the Act, while permitting the accused to establish as a defence that they lacked that mental state. The provision defines culpable mental state to include intention, motive, knowledge, and belief (or reason to believe) and confirms that facts are proved only when the court is satisfied of their existence beyond reasonable doubt rather than by a preponderance of probability.