The competence of a witness determines whether he would be heard by a court to give evidence and compellability depends on the question whether a witness has a legal obligation to give evidence if called upon to do so and which the court can enforce upon. When a court lawfully receives his evidence, the witness is said to be competent and when the court may require him to give evidence over his objection the witness is said to be compellable. The general rule of English law states that all witnesses are both competent and compellable. This rule was convenient in view of the assumption that the court must give access to as much relevant and admissible evidence as possible. At common law, however, there were various exceptions to this general rule. The Courts have been deprived of many relevant and cogent evidences owing to the scope of such exceptions. Presently, these exceptions are no longer applied. Thus, for the purpose of civil cases, the common law rule of general competence is adequate. However, problems relating to competency of witnesses arise mostly in criminal cases. The Youth Justice and Criminal Evidence Act, 1999 establishes a general statutory rule of competence in criminal cases. The significance of the principle that evidence in general should be given under oath or affirmation but requires unsworn evidence to be given in the cases of certain child witnesses and witnesses who are deemed to be incapable of taking the oath is upheld by the 1999 Act.
