What is the test for admitting further evidence after the conclusion of the trial?

In exercising my discretion to admit further evidence after the conclusion of the trial, I consider the bearing of the further evidence upon the case in light of the evidence already heard at trial. I recognize that, in keeping with the authorities reviewed in Brasseur v. York, a more relaxed standard of admission is appropriate given that a decision has not yet been rendered. However, at the same time, the authorities are clear that it remains the exceptional case where a motion to adduce further evidence following the conclusion of the hearing of the trial should be allowed.