(1) In criminal proceedings, the hearsay rule and the tendency rule do not prevent the admission or use of evidence of an opinion about a defendant adduced by another defendant where—
(a) the person whose opinion it is has specialised knowledge based on the person's training, study or experience; and
(b) the opinion is wholly or substantially based on that knowledge.
(2) Where evidence of an opinion as mentioned in subsection (1) has been admitted, the hearsay rule, the opinion rule and the tendency rule do not prevent the admission or use of evidence that tends to prove that that evidence should not be accepted.