The general rule is that the Crown is not allowed to split its case. The Crown must enter all the clearly relevant evidence it has, or that it intends to rely upon, to establish its case with respect to the issues raised in the indictment and any particulars.
The rule is intended to ensure 1) that trials are not unduly prolonged and 2) that the accused knows the full case that must be met before s/he responds.
However, where the defence evidence raises a new matter, a new fact, or a defence which the Crown had no opportunity to deal with, or could not have reasonably anticipated, the Crown may be allowed to call evidence in rebuttal after completion of the defence case. Further, evidence which is marginally relevant, and thus strictly speaking admissible as part of the Crown case in chief, may nonetheless be admissible in reply where it takes on real significance only because of a position advanced during the defence case. Another way of saying the same thing, adopted in several Canadian cases, is that the matter to which the proposed reply evidence relates only became a “live issue” once the defence put in its case. The trial judge has discretion to admit such evidence in reply/rebuttal.
However, rebuttal will not be permitted regarding matters which merely confirm or reinforce earlier evidence adduced in the Crown’s case which could have been brought before the defence was made.
R v Sanderson, 2017 ONCA 470 at paras 32-45; see also R v Graziano, 2015 ONCA 491 at paras 34-40