s 53 Competence of witnesses to give evidence.
(1) At every stage in criminal proceedings all persons are (whatever their age) competent to give evidence. (2) Subsection (1) has effect subject to subsections (3) and (4). (3) A person is not competent to give evidence in criminal proceedings if it appears to the court that he is not a person who is able to— (a) understand questions put to him as a witness, and (b) give answers to them which can be understood. (4) A person charged in criminal proceedings is not competent to give evidence in the proceedings for the prosecution (whether he is the only person, or is one of two or more persons, charged in the proceedings). (5) In subsection (4) the reference to a person charged in criminal proceedings does not include a person who is not, or is no longer, liable to be convicted of any offence in the proceedings (whether as a result of pleading guilty or for any other reason).