Evidence which is relevant to the question whether the defendant has a propensity to be untruthful is admissible on that basis under section 101(1)(e) only if the nature or conduct of his defence is such as to undermine the co-defendant's defence.
Only evidence—
which is to be (or has been) adduced by the co-defendant, or
which a witness is to be invited to give (or has given) in cross-examination by the co-defendant,
is admissible under section 101(1)(e).