Lambert v Peachman 2017 ONSC 4270 outlined the law relating to what is necessary in the form of new evidence to re-open a trial.
26 The principles and authority to re-open evidence of a trial are well established and noted by the Supreme Court of Canada in Sagaz Industries Canada Inc., Sagaz Industries Inc. and Joseph Kavana v. 671122 Ont Limited, formerly Design Dynamics Limited  2 R.C.S. to fall within the trial judge’s discretion but to be used “sparingly and with the greatest care”.
27 The Court is concerned with never ending litigation. The competing tensions are between finality to the hearing process and the need to prevent unduly protracted legal proceedings against the need to ensure that important and relevant evidence is not ignored, since doing so might lead to a substantial injustice (See Justice P. Lauwers at par. 16 in Jackson v. Corp. of the City of Vaughan, 2009 CanLII 717 (ONSC).
Test to Admit New Evidence
28 The test to re-open evidence of a trial to admit new evidence, is a two-prong test, both parts of which must be satisfied by the moving party:
- First, could the evidence have been obtained before trial by the exercise of reasonable diligence?
- Second, would the evidence, if presented at trial, probably have changed the result?
Availability of Evidence at Trial and Reasonable Diligence
29 The reasonable diligence requirement may be “relaxed in exceptional circumstances where necessary to avoid a miscarriage of justice” (See Degroote v. Canadian Imperial Bank of Commerce,  O.J. No. 2313 (C.A.) at p. 2.). To avoid a miscarriage of justice a “trial judge has the discretion to permit a matter to be reopened and new evidence to be admitted even if the evidence could have been placed before the Court in the first instance” (See 130734 Ontario Inc. v. 1243058 Ontario Inc.,  O.J. No. 257).
30 Nordheimer J. noted at p. 3 – 4 in 1307347 Ontario Inc.:
It is also my view that a miscarriage of justice involves more than just a finding that a different result might have occurred. It involves a finding that, absent the reopening of the matter and the reversal of the original determination, a fraud would be perpetrated or the giving of perjured evidence or the deliberate misleading of the court would be countenanced.
31 In Qit Fer et Titane Inc. v. Upper Lakes Shipping Ltd. (1991), 3 O.R. (3D) 165, at p. 168, Gravely J. suggested that fraud was the usual requirement, but it may not be the only basis to find a miscarriage of justice:
Where justice demands it and particularly where fraud is involved or the court may have been deliberately misled, a judge is justified in departing from the diligence requirement in order to prevent a miscarriage of justice.