[35] Although what was said in Niven was directed to s 371(i) of the Criminal Code (Tas), the principles which it states apply equally to this case. Indeed, there is no reason to think that they do not apply generally to the trial of indictable crime in Australia, unless and until this aspect of the practice and procedure in such trials is explicitly modified by statute.
17 I do not believe that there is anything in the line of authority to which I have referred or the principle that the Crown must not split its case, that would prevent the Crown from adducing evidence of a psychiatrist, as to the mental state of the accused at the time of the killing, to rebut evidence in support of the defence under s 23A and where that evidence is not otherwise relevant to prove the offence. In so far as Dawson J stated anything in Chin to the contrary, I believe it is inconsistent with other statements made in the cases to which I have referred and, in particular, with what was said in the joint judgment of Gibbs CJ and Wilson J in Chin in the passage quoted above. There is nothing in Soma that suggests that the principle is not as stated in the joint judgment. In Soma the evidence called in reply contained evidence of admissions in proof of the offence charged.
18 Having regard to what was said by McHugh J in Melbourne and simple logic, I cannot see any rational policy that would require the Crown to call evidence, which is admissible and relevant only to rebut a defence under s 23A, in its case. I can appreciate why the Crown cannot choose to split its case in reply so that, if it calls evidence in its case-in-chief for the purpose of rebutting the defence, it may not be permitted to call further evidence in reply. The principle enunciated in the High Court decisions, to which I have referred, is concerned with the proper application of the onus of proof on the Crown and fairness to the accused. I fail to see how generally speaking it could be unfair to the accused to permit the Crown to call evidence of a psychiatric nature in reply to evidence in proof of a defence of substantial impairment where the onus to prove that defence is on the accused.
19 But whatever may have been the situation at common law, it seems clear to me that the principle has been affected by s 151(3). I can see no reason why that section should be construed other than in accordance with its terms and unaffected by any common law rule that it may have displaced.
20 On its face s 151(3) provides the Crown generally with a discretion as to whether to call evidence to rebut the defence under section 23A either in its case-in-chief or in reply. However, in an appropriate case the trial judge may be required to intervene and give a direction as to when that evidence should be called. This will usually be necessary because it would be unfair to the accused if the evidence were to be adduced in reply. The need for that direction might arise, for example, because the evidence relied on by the Crown is part of the facts and circumstances surrounding the killing and, therefore, would more appropriately be adduced in the Crown case. Another example may be where the evidence has a prejudicial effect that might operate unfairly against the accused if it were the last evidence to be heard by the jury. Yet another example may be where, although the evidence is tendered to rebut the defence, it is also relevant to either establish or disprove an element in the Crown case, such as an intention to kill.
21 But where the evidence is expert opinion given by a professional such as a psychiatrist or medical practitioner, and is relevant only because the defence intends to rely upon s 23A, I find it difficult to see how the intervention of the Court to interfere with the discretion vested in the Crown by s 151(3) could usually be justified let alone warranted.
22 There is no novelty, in this State, in the fact that a provision has displaced the common law principle against the Crown splitting its case. In relation to alibi evidence it has long been the case that, contrary to the common law rule, the prosecution has had a discretion whether to call the evidence rebutting alibi in its case or in reply. Section 405A(4) of the Crimes Act, before the repeal of that section, stated: