Juries (Civil) - Secrecy. R v Kum
In the criminal matter of R v Kum (Ont CA, 2015) the Court of Appeal commented as follows on the rule of secrecy of jury proceedings:
The secrecy of the jury’s deliberations
 In R. v. Pan; R. v. Sawyer, 2001 SCC 42 (CanLII),  2 S.C.R. 344, Arbour J. discussed in detail the rules regarding jury secrecy. Under the common law rule of jury secrecy, also known as Lord Mansfield’s rule, evidence of what occurred in the jury room among the jurors is not admissible in subsequent proceedings: Pan, at para. 54. The issue often arises when the jury’s verdict is sought to be impeached, as in the Pan and Sawyer cases.
 In Pan, Arbour J. also discussed the policy reasons behind the jury secrecy rules, which, she pointed out, have evolved over time. The common law jury secrecy rule, together with the prohibition on disclosing information relating to the jury’s proceedings under s. 649 of the Criminal Code, promotes candour and “free and frank debate among jurors, protecting jurors from harassment, and preserving public confidence in the administration of justice”: Pan, at para. 89. As she stated at para. 50: “While searching for unanimity, jurors should be free to explore out loud all avenues of reasoning without fear of exposure to public ridicule, contempt or hatred.”
 However, there is an exception to Lord Mansfield’s rule. Evidence that the jury was exposed to some extrinsic information or influence from outside the proceeding is admissible: Pan, at para. 55. But even if jurors are allowed to testify about whether they were exposed to any extrinsic information, the court should not admit evidence from the jurors as to what influence that information had on their deliberations: Pan, at para. 59.
 Justice Arbour concluded her discussion by restating a modern version of Lord Mansfield’s common law jury secrecy rule as follows at paras. 77 and 78:
 In light of the above, in my view a proper interpretation of the modern version of Lord Mansfield’s rule is as follows: statements made, opinions expressed, arguments advanced and votes cast by members of a jury in the course of their deliberations are inadmissible in any legal proceedings. In particular, jurors may not testify about the effect of anything on their or other jurors’ minds, emotions or ultimate decision. On the other hand, the common law rule does not render inadmissible evidence of facts, statements or events extrinsic to the deliberation process, whether originating from a juror or from a third party, that may have tainted the verdict.
 This modern formulation of the rule, which reflects the approach of the majority of the Court of Appeal, best ensures that the sanctity of the jury’s deliberations is preserved by promoting in equal measure the secrecy and confidentiality indispensable to the deliberation process and the exposure of serious matters casting doubt on the integrity of the verdict.