This chapter focuses on the right to be presumed innocent, one of the most ancient and important principles of criminal justice, and a prerequisite for any system based on the rule of law. The right is absolute and non-derogable and, at its core, prohibits convictions that are predetermined or based on flimsy grounds. International human rights bodies have therefore found that where a conviction is based on non-existent, insufficient, or unreliable evidence, the presumption has been violated and a miscarriage of justice has occurred. More frequently, international human rights bodies have applied the presumption to require specific procedural protections during a trial. These include guarantees that the prosecution bears the burden of proving a defendant’s guilt beyond reasonable doubt, and that the defendant should not be presented or described as a criminal before he has been proved to be one. The chapter concludes that the presumption is protected in similar terms in international human rights treaties, but also highlights divergences in international jurisprudence relating to the standard for finding that a court’s assessment of evidence violates the presumption, the permissibility of reversing the burden of proof, and the extent to which the presumption applies after a trial has been completed.