Criminal - Appeals - Re-openings. R. v. Hepfner
In R. v. Hepfner (Ont CA, 2023) the Court of Appeal considered the test for re-opening, here a summary conviction criminal appeal:
 The circumstances in which a court may permit the re-opening of an appeal are closely circumscribed: R. v. Smithen-Davis, 2022 ONCA 832, 421 C.C.C. (3d) 56, at para. 31. The moving party has not established a clear and compelling case that a miscarriage of justice will likely occur absent a re-opening. Finality is an important principle and prevails in this case.. R. v. R.G.
In R. v. R.G. (Ont CA, 2023) the Court of Appeal considers the law of 're-opening' a trial, here in a criminal trial context (but the law is largely applicable to both civil and criminal) and involving fresh evidence issues:
 A trial judge sitting without a jury has the jurisdiction to vacate an adjudication of guilt and reopen a trial prior to the imposition of sentence. For good reason, this is rarely done. In determining whether to invoke this jurisdiction, the trial judge will consider numerous factors, including whether the defence has exercised due diligence during the trial proper. In exceptional cases, the cogency of new evidence will be so strong that, despite a failure of due diligence, the interests of justice will demand that the finding of guilt be vacated and the trial reopened. This is one of those rare, exceptional cases.
The Law on Reopening
 Trial judges sitting without a jury are not functus officio until after sentence is imposed or the case is otherwise disposed of. To be sure, a trial judge sitting without a jury can vacate an adjudication of guilt prior to sentence or other final disposition: R. v. Lessard (1976), 1976 CanLII 1417 (ON CA), 30 C.C.C. (2d) 70 (Ont. C.A.), at p. 73. But to be equally sure, this jurisdiction should be exercised only in “exceptional circumstances” where “its exercise is clearly called for”: Lessard, at p. 73. This is a rare power and no one should expect a do-over: R. v. Griffith, 2013 ONCA 510, 116 O.R. (3d) 561, at para. 23.
 Since the trial judge is operating within an area of discretion when deciding whether to reopen a case, the decision is entitled to significant deference on appeal unless of course the decision is infected by legal error, a material misapprehension of evidence or is unreasonable: R. v. M.G.T., 2017 ONCA 736, 357 C.C.C. (3d) 109, at para. 55; R. v. Kippax, 2011 ONCA 766, 24 M.V.R. (6th) 1, at para. 64, leave to appeal refused,  S.C.C.A. No. 92; and Palmer v. The Queen, 1979 CanLII 8 (SCC),  1 S.C.R. 759, at p. 777. Here, the appellant maintains that the decision is infected by legal error. I will explain those errors shortly below.
 The Palmer test for the admission of fresh evidence on appeal guides the analytical approach on applications to reopen. The four-part Palmer test, at p. 775 of that decision, is well-established:
(1) The evidence should generally not be admitted if, by due diligence, it could have been adduced at trial provided that this general principle will not be applied as strictly in a criminal case as in civil cases. Over time, this test has been distilled into three helpful broad considerations: (1) is the evidence admissible under the operative rules of evidence (the admissibility component); (2) is the evidence sufficiently cogent in that it could reasonably be expected to have affected the verdict (the cogency component); and (3) does the party seeking its admission offer a satisfactory explanation for the failure to adduce it at trial (the due diligence component): R. v. Truscott, 2007 ONCA 575, 225 C.C.C. (3d) 321, at para. 92.
(2) The evidence must be relevant in the sense that it bears upon a decisive or potentially decisive issue in the trial.
(3) The evidence must be credible in the sense that it is reasonably capable of belief.
(4) The evidence must be such that if believed it could reasonably, when taken with the other evidence adduced at trial, be expected to have affected the result.
The Application of Due Diligence
 Due diligence retains an essential purpose at reopening applications. Certainty and finality demand that everyone put their best foot forward at trial. Without a robust application of the due diligence criterion, trials would become trial runs, institutional concerns would abound, and victims would be endlessly revictimized. The integrity of the administration of justice simply cannot invite the relaxation of expectations that all, including defence counsel, advance their cases – their whole cases – the first time around.
 Therefore, as in Palmer, evidence should generally not be admitted on a reopening application where, through due diligence, it could have been adduced during the trial proper. At the same time, as this court and the Supreme Court have repeatedly noted, from time-to-time in criminal cases, failures to exercise due diligence will bend to cogency, especially where miscarriages of justice loom: R. v. Kowall (1996), 1996 CanLII 411 (ON CA), 108 C.C.C. (3d) 481 (Ont. C.A.), at pp. 493-94, leave to appeal refused,  1 S.C.R. viii; R. v. Warsing, 1998 CanLII 775 (SCC),  3 S.C.R. 579, at p. 592; R. v. J.A.A., 2011 SCC 17,  1 S.C.R. 628, at para. 8; R. v. Hay, 2013 SCC 61,  3 S.C.R. 694, at paras. 64-67; and R. v. Reeve, 2008 ONCA 340, 233 C.C.C. (3d) 104, at paras. 83-89. In other words, due diligence is not a precondition to admissibility: Truscott, at para. 93. As noted by Rothstein J. at para. 67 of Hay, where the appellant sought the admission of evidence on appeal that his trial counsel had not inquired into:
In general, mere lack of knowledge on the part of trial counsel without any indication that he inquired into the possibility of obtaining and presenting the evidence is a factor against admitting the evidence for the first time on appeal: McMartin, at pp. 490-91. However, [since] this is a criminal case, involving charges of the most serious nature, I would not allow the evidence to be excluded solely [based on] a lack of diligence.