The doctrine of issue estoppel arises out of the broader doctrine of res judicata
(literally “a matter decided”) and provides that a factual issue that is decided in one proceeding must be accepted and cannot be relitigated in another proceeding unless the earlier decision is set aside on appeal. The purpose of the doctrine is to ensure fairness to the accused, avoid inconsistent verdicts and maintain the principle of finality: R. v. Mahalingam
, 2008 SCC 63
,  3 S.C.R. 316, at paras. 2
, 38. In the criminal context, there are three requirements that must be met for the doctrine to apply.
 First, the issue must have been decided in favour of the accused in the prior proceeding, that is, the finding must be logically necessary to the verdict of acquittal: Mahalingam, at para. 53; R. v. Punko, 2012 SCC 39,  2 S.C.R. 396, at paras. 7-8. This is a factual issue which the defence bears the onus of establishing: Mahalingam, at paras. 26, 52. Whether the issue was resolved in the accused’s favour on the basis of a positive factual finding or a reasonable doubt does not matter for the purposes of the doctrine: Mahalingam, at paras. 22-23, 28; R. v. Grdic,  S.C.R. 810, at p. 825.
 Second, the determination of the issue must be final. Issues determined at trial are final, unless set aside on appeal: Mahalingam, at para. 55.
 Third, there must be mutuality, that is, the parties must be the same in both the earlier and the subsequent proceedings: Mahalingam, at para. 56.
 The doctrine of issue estoppel clearly applies in this case. The issue of whether the complainant consented to sexual activity with the applicant at the time the video was made was clearly decided in his favour at the first trial. The applicant’s identity was not in issue, nor was there any issue that there had been sexual contact between him and the complainant (which the video conclusively demonstrated). The only issue at the first trial was whether the complainant had consented. The first trial judge was not satisfied beyond a reasonable doubt that she had not.
 The other two requirements for the application of the doctrine are also met. As there was no appeal of the acquittal, the first trial judge’s findings are final, and the parties to both proceedings, J.C. and the Crown, are the same.
 In my view, there are several reasons why despite the positions of the parties, the Crown should not be permitted to lead evidence that the complainant did not consent to the sexual activity in the video.
(b) No Residual Discretion