9.—(1) Evidence which is relevant to the question whether the defendant has a propensity to be untruthful is admissible on that basis under Article 6(1)(e) only if the nature or conduct of his defence is such as to undermine the co-defendant’s defence.
(2) Only evidence—
(a)which is to be (or has been) adduced by the co-defendant, or
(b)which a witness is to be invited to give (or has given) in cross-examination by the co-defendant,
is admissible under Article 6(1)(e).