(1)  The credibility rule does not apply to evidence given by a person concerning the credibility of another witness if –

(a) the person has specialised knowledge based on the person's training, study or experience; and

(b) the evidence is evidence of an opinion of the person that –

(i) is wholly or substantially based on that knowledge; and

(ii) could substantially affect the assessment of the credibility of the witness; and

(c) the court gives leave to adduce the evidence.

(2)  To avoid doubt, and without limiting subsection (1)  –

(a) a reference in that subsection to specialised knowledge includes a reference to specialised knowledge of child development and child behaviour (including specialised knowledge of the impact of sexual abuse on children and their behaviour during and following the abuse); and

(b) a reference in that subsection to an opinion of a person includes, if the person has specialised knowledge of that kind, a reference to an opinion relating to either or both of the following:

(i) the development and behaviour of children generally;

(ii) the development and behaviour of children who have been victims of sexual offences, or offences similar to sexual offences.