This article examines the incidence of a threshold burden of proof in admissibility challenges based on s 35(5) of the South African Constitution. The following question is asked: Should the accused bear the onus of showing that his or her fundamental right has been infringed during the evidence gathering process, or should the prosecution bear the burden of proving that the disputed evidence has been obtained in a constitutional manner? South African case law and the opinions of scholarly writers are incompatible on this issue. This article explores the conflicting lines of reasoning followed by the Supreme Court of Appeal in Director of Public Prosecutions, Transvaal v Viljoen, and the full bench decision of the Transvaal Provincial Division (now Northern Gauteng) in S v Mgcina. The author concludes that, having regard to a contextual interpretation of s 35(5) and the textual differences between s 24(2) of the Canadian Charter and s 35(5), the accused should not be saddled with a threshold burden. The prosecution should therefore bear the onus of showing that the evidence has been obtained in a constitutional manner, once the accused alleges that it has been obtained in violation of his or her rights.