Our trial system is based on the calling of witnesses and, as a general rule, the court is entitled to every person’s evidence, provided the person is competent to testify.1Competency means that the person is qualified or capable of giving evidence. Should the person not wish to testify, he can be forced or compelled to do so. The person is served with a subpoena. A subpoena ad testificandum requires that the person attend to give evidence. A subpoena duces tecum requires not only that the person attend to give evidence but that the person also bring anything in his possession or control that relates to the charge and, more particularly, those things specified in the subpoena. Should the person fail to attend, a warrant may be issued for his arrest and the person may be found guilty of contempt of court.2At common law, many potentially valuable witnesses were rendered incompetent to testify. The common law judges were concerned about the giving of inaccurate or perjured testimony. Therefore, at common law people were precluded from testifying on grounds of interest, infamy (should the witness have a criminal history), infancy, insanity, disbelief in a Supreme Being, and marriage. Fortunately, most of the common law rules barring certain persons from testifying have been
swept aside by statute. For example, all the provincial Evidence Acts have a provision comparable to section 3 of the Canada Evidence Act, which reads:
A person is not incompetent to give evidence by reason of interest or crime.
Today, for the most part, all potential witnesses are allowed to testify - warts and all; their frailties are left as a matter...