The Latin maxim 'actus non facit reum nisi mens sit rea' is a fundamental principle in criminal law. It means that a prohibited act alone does not constitute a crime - there must also be a guilty mind (mens rea). Option D correctly captures this by stating that both the prohibited act AND the guilty intention must be present for an offence to be constituted. Option A incorrectly focuses only on the act, while Option B focuses only on intention. Option C is wrong because either element alone is insufficient.