(1) Subject to section 18 and section 19, and to subsection (2) of this section, communications data submitted as evidence in any proceedings under this Act shall be admissible in evidence in accordance with the law relating to the admissibility of evidence.
(2) In admitting into evidence any communications data referred to in subsection (1)—
(a) no question shall be asked of any witness that discloses or might result in the disclosure of any of the details pertaining to the method by which the data was obtained of the identity of any party who supplied the data;
(b) a statement by the witness that the data was obtained by virtue of a disclosure order under section 21 shall be sufficient disclosure as to the source or origin of the data; and
(c) in proving the truth of a statement referred to in paragraph (b), the witness shall not be asked to disclose any of the matters referred to in paragraph (a).
(3) Subsection (2) shall not apply to any proceeding in respect of an offence under this Act but if the court is satisfied that—
(a) the disclosure is would be likely to jeopardise the course of any investigations or be prejudicial to the interests of national security; and
(b) the parties to the proceedings would not be unduly prejudiced thereby, the court shall not require or permit disclosure of the matters referred to in subsection (2)( a).