The Crown should use an opening to introduce the parties, explain the process, and provide a general overview of the evidence the Crown anticipates calling in support of its case. The Crown should not refer to evidence the admissibility of which is in dispute. For example, since a statement or confession an accused person made to a person in authority does not become evidence until ruled admissible, Crown counsel should not refer to it in an opening: R v Clause, 2016 ONCA 859 at paras 32-33
In closing addresses, counsel, both prosecuting and defending, are entitled to make submissions about the effect of absence of evidence of a forensic connection between an accused and the scene of a crime. What they can say is bounded by the evidence given at trial and subject to the prohibition against counsel, especially Crown counsel, putting before the jury, as facts for their consideration, matters of which there is no evidence: R v Hassanzada, 2016 ONCA 284 at para 72
A trial judge has the authority, in some cases the duty, to define the extent to which counsel may discuss a subject in their final addresses and to balance what is said there with an instruction to the jury on the same subject-matter: Hassanzada at para 73
For more on the law on the bounds of a crown closing in jury trials, see: R v Taylor, 2015 ONCA 448
The Crown is afforded considerable latitude when making a closing address. But forceful advocacy has clear limits and in making closing submissions, the Crown “should not … engage in inflammatory rhetoric, demeaning commentary or sarcasm, or legally impermissible submissions that effectively undermine a requisite degree of fairness”: R v John, 2017 ONCA 615 at para 77, [citations omitted]
When improper comments by Crown counsel are sufficiently prejudicial, a trial judge has a duty to intervene; a failure to do so will constitute an error of law.
Where, for example, the Crown refers in its opening to anticipated evidence that subsequently is not led or is ruled inadmissible, it is the duty of the trial judge to tell the jury explicitly that the statements complained of are not in evidence and they must try to free their minds from them:
Where a trial judge fails to redress properly the harm caused by a clearly unfair or significantly inaccurate jury address, a new trial may result. The question is whether, in the context of the entire trial, the remarks and the trial judge’s response or failure to respond caused a substantial wrong or miscarriage of justice: R v Clause, 2016 ONCA 859 at paras 38-39