R. v. Berbeck, 2013 ONCA 241 reminds us of the heavy burden the Crown faces on appealing an acquittal:
 In R. v. Graveline, 2006 SCC 16,  1 S.C.R. 609, the majority of the Supreme Court of Canada set out the Crown's burden when it appeals the acquittal of an accused. At para. 14 of his reasons, Fish J. for the majority stated:
It has been long established, however, that an appeal by the Attorney General cannot succeed on an abstract or purely hypothetical possibility that the accused would have been convicted but for the error of law. Something more must be shown. It is the duty of the Crown in order to obtain a new trial to satisfy the appellate court that the error (or errors) of the trial judge might reasonably be thought, in the concrete reality of the case at hand, to have had a material bearing on the acquittal. The Attorney General is not required, however, to persuade us that the verdict would necessarily have been different.
This burden on the Crown, unchanged for more than half a century (seeCullen v. The King,  S.C.R. 658), was explained this way by Sopinka J., for the majority, in R. v. Morin,  2 S.C.R. 345:
I am prepared to accept that the onus is a heavy one and that the Crown must satisfy the court with a reasonable degree of certainty. An accused who has been acquitted once should not be sent back to be tried again unless it appears that the error at the first trial was such that there is a reasonable degree of certainty that the outcome may well have been affected by it. Any more stringent test would require an appellate court to predict with certainty what happened in the jury room. That it cannot do. [Internal citation omitted.]
Speaking more recently for a unanimous court in R. v. Setton,  2 S.C.R. 595, 2000 SCC 50, the Chief Justice stated:
The parties agree that acquittals are not lightly overturned. The test as set out in Vézeau v. The Queen,  2 S.C.R. 277, requires the Crown to satisfy the court that the verdict would not necessarily have been the same had the errors not occurred. In R. v. Morin,  2 S.C.R. 345, this Court emphasized that "the onus is a heavy one and that the Crown must satisfy the court with a reasonable degree of certainty". [Internal citation omitted.]
 It is clear from the authorities that the Crown's burden in these circumstances is a heavy one.