At common law the "principle against self-incrimination" supported only two self-incrimination rules. The first was the "privilege against self-incrimination" which enabled witnesses to refuse to answer questions in a formal proceeding if their answers would tend to incriminate them. The second rule prevented the Crown from calling the accused as a witness during his own trial. Until a little over 100 years ago, this second rule did not exist. This is because the accused was not allowed to testify at all, even if he wanted to, due to concerns that his obvious interest would cause him to testify falsely. When the accused was finally made competent, he was made competent only for the defence, thereby giving rise to the non-compellability protection.
At the same time that this non-compellability rule was adopted, the common law "privilege against self-incrimination" was removed by statute. It was replaced by rules giving witnesses a protection (as opposed to a privilege) against self-incrimination, under which they would be made to answer self-incriminating questions on the understanding that their answers could not be used to incriminate them in a subsequent proceeding. In effect, the witnesses were given what is often referred to as "use immunity."
These self-incrimination rules have been modified by the Charter. "The jurisprudence of our [Supreme] Court on self-incrimination developed such that three procedural safeguards emerged, use immunity, derivative use immunity, and constitutional exemption."23In essence, the Charter now provides witnesses with an aggressive form of the "use immunity" described above, as well as a new "derivative use immunity" which can cause not only the testimony of a witness to be protected, but even other evidence derived from, or found as a result of, that testimony. The third procedural...