“I am of the view that the evidence should be admitted in the circumstances. In N.H v. J.H., [2017 ONSC 4414 (CanLII)] the Court, which entertained a motion to introduce new evidence while a trial decision was under reserve, the Court made the following comments on the propriety of the trial judge receiving new evidence, which I find apt in the present case:
19 Perhaps there is some confusion as to when a trial begins and finishes. That should be dispelled.
20 It is trite law, that a trial judge remains seized of the issues before her until a formal order or judgment is entered in the court record. There are several cases that stand for the proposition that a judge is not functus officio until the order is formalized. On the other hand, this does not mean that trials should be converted to rolling ongoing interminable hearings. Once the court has released a decision, it would be a rare case where it might be in the interests of justice to withdraw reasons of the court and to rehear the case on the merits. I make this point simply to emphasise that in certain circumstances a trial judge could re-open the hearing even if she had released her reasons. The trial is not technically concluded until the judgment is entered. In my view the trial is still in progress.
21 Trials are of course subject to formal procedures. Just because the decision is under reserve and the trial is still in progress, does not confer upon the parties or the trial judge a licence to continually entertain additional evidence. Generally speaking a party must marshal all of its evidence and present it during the trial. The party is not permitted to try to bring more evidence to bolster its case after that party’s case is closed. It is for that reason that rules and principles have evolved concerning this issue of re-opening the case. Justice Mackinnon referred to them when she gave leave to the applicant to re-open his case in April. She referred with approval to the factors outlined in Hughes v. Roy. Amongst those factors are whether the evidence is relevant, necessary and reliable, whether it could have been obtained before the trial by the exercise of reasonable diligence and whether it would cause a miscarriage of justice if the new evidence were not accepted.
….
23 It is certainly possible that the change in circumstances which has taken place since the parties closed their cases would meet the test for re-opening the trial. There can be no question that the trial judge has that authority at a time when she has not yet released her decision. Whether to entertain that evidence or to re-open the trial is a decision for her and her alone and it would not be appropriate for a motions judge to entertain that evidence on a motion while the decision remains under reserve.”
Anderson v. McIntosh-Anderson, 2018 ONSC 4688 (CanLII) at 113