Evidence Obtained by Cruel, Inhuman or Degrading Treatment: Why the Convention Against Torture’s Exclusionary Rule Should be Inclusive

Convention against Torture (CAT) prohibits admissibility of evidence obtained by torture but fails to extend similar prohibition to evidence obtained by cruel, inhuman or degrading treatment (CIDT evidence). Manfred Nowak argues that CAT\u27s failure to prohibit CIDT evidence can be resolved if in interpreting torture we take the purposive element, instead of severity, as the main element that distinguishes torture from CIDT. He argues that both torture and CIDT require infliction of severe pain and thus it must be the purpose for which severe pain was inflicted that distinguishes torture from CIDT. If the purposive element is key in distinguishing torture from CIDT, then there is no need to have separate prohibition of CIDT evidence because whenever CIDT is applied for a specific purpose, it becomes torture and consequently subject to CAT\u27s prohibition on torture evidence. This paper will first assess Nowak\u27s approach and argue that it is neither supported by CAT\u27s negotiation history, nor by subsequent case law and scholarship. Then it will propose that general principles of law provide better guidance. To demonstrate this, it first defines general principles of law to constitute fundamental legal norms that are common to different legal systems. With regard to how to derive a general principle of law, it examines three primary approaches: comparativist, systems and categorist. The paper favors systems approach, which requires analyzing only representative sample of world\u27s legal systems to determine the existence of relevant general principle of law. After that, to establish the existence of a general principle of law that prohibits CIDT evidence, the paper analyzes national laws of twelve different countries: Canada, United States, Argentina, Mexico, Germany, United Kingdom, France, Japan, China, Russia, South African and Uganda. The paper focuses on how the national laws of these countries regulate admissibility of evidence obtained by CIDT. It pays specific attention to the question of whether they differentiate between torture and CIDT for the purposes of exclusionary rule. Such an examination will reveal that national laws under consideration prohibit admissibility of both torture and CIDT evidence. Consequently, the paper concludes that there is already a rule in international law that prohibits (through a general principle of law) admissibility of CIDT evidence