For the purposes of section 101(1)(g) a defendant makes an attack on another person's character if—
he adduces evidence attacking the other person's character,
he (or any legal representative appointed under section 38(4) of the Youth Justice and Criminal Evidence Act 1999 (c. 23) to cross-examine a witness in his interests) asks questions in cross-examination that are intended to elicit such evidence, or are likely to do so, or
evidence is given of an imputation about the other person made by the defendant—
on being questioned under caution, before charge, about the offence with which he is charged, or
on being charged with the offence or officially informed that he might be prosecuted for it.
In subsection (1) "evidence attacking the other person's character" means evidence to the effect that the other person—
has committed an offence (whether a different offence from the one with which the defendant is charged or the same one), or
has behaved, or is disposed to behave, in a reprehensible way;
and "imputation about the other person" means an assertion to that effect.
Only prosecution evidence is admissible under section 101(1)(g).