The principle against self-incrimination refers to the idea that an individual cannot be compelled to assist in her own prosecution. In the pre-Charter era, the view prevailed that no overarching principle against self-incrimination existed in Canadian law. While certain discrete legal rules were recognized as protecting suspects against compulsory self-incrimination, these rules were not thought to reflect or constitute any independent, functional legal principle. Since the advent of the Charter, however, an overarching principle against self-incrimination has been recognized as one of the principles of fundamental justice. This constitutional principle has come to be understood as undergirding a number of pre-existing legal rules, and has also become a source of new legal protections. This paper discusses the development and justifications of the principle against self-incrimination and traces the expression of that principle through various legal doctrines. Particular attention is paid to the distinction between free choice and compulsion that separates permissible and impermissible self-incrimination. The author argues that serious inconsistencies persist in the law’s treatment of self-incrimination, and that the “patchwork” quality of the principle against self-incrimination is due, in part, to the courts’ inconsistent approach to the problem of compulsion in the self-incrimination context. The author uses undercover operations as an example of a context where the current law provides inadequate protection against self-incrimination and discusses how a more coherent approach to the problem of compulsion might vindicate the overarching principle against self-incrimination as a constitutional norm.