When and to what extent should an appellate court, on an appeal against conviction, inquire into an allegation that a juror was biased? Should an appellate court hear the evidence of the juror and allow cross-examination?
These issues of principle were decided in Rolleston v R  NZSC 113 (reasons judgment delivered on 19 October 2020).
If the power to order an inquiry is not specifically provided for by statute, the court has inherent power to address irregularities in its process by such means as may be necessary in the interests of justice (at ).
Because of statutory limitation, evidence may not be given about the deliberations of a jury (intrinsic evidence), except in exceptional circumstances giving compelling reason to allow such evidence: Evidence Act 2006, s 76(1). This is the “secrecy rule”, discussed at -.
However, extrinsic evidence (that is, evidence not involving the actual deliberations of the jury) will be admissible if it is evidence of disqualifying juror conduct or knowledge (at ).
An inquiry into whether one juror’s attitude to the defendant may have affected other jurors would be an inquiry into intrinsic jury deliberations and would need to clear the high threshold in s 76(3): see .
Whether an inquiry should be conducted depends on the interests of justice, which depend on the circumstances of the trial and the various fair trial safeguards to ensure a fair trial (at , the safeguards are summarised at -).
Allegations that, if true, would be inconsequential, trivial, or irrelevant, or that relate to evidence that would be inadmissible, are insufficient to require an inquiry (at ). Further, a conservative approach to ordering an inquiry may be appropriate to protect jurors from fishing expeditions unsupported by credible evidential narrative (at ).
But an inquiry will generally be in the interests of justice where allegations relate to extrinsic evidence and are sufficiently credible to suggest an inquiry could reasonably establish that there has been a miscarriage of justice (at ).
On the facts here an inquiry was appropriate (). The authorities are unclear on whether, if bias was established, it would necessarily have infected the whole jury (at , but Glazebrook J held that it would have: ). In any event, the inquiry here, conducted by senior counsel who interviewed and obtained a signed statement from the juror, did not disclose any bias.
Cross-examination of a juror may be justified, but leave to cross-examine will be rarely given (at ). The interests of justice will again be the criterion, and cross-examination may be necessary where an inquiry is for some reason insufficient. For example, the credibility of the juror’s account may be directly in issue (at ), but that was not the case here.
Counsel’s report did not contain anything to suggest the juror’s statement may have been unreliable, and there was no real conflict on the essential questions (here: the juror was staring at the defendant's brother who was in the public gallery for most of the trial; the juror had been bullied at school three years earlier by the defendant’s brother). The juror’ statement and the brother’s affidavit were in agreement, but the juror said that during the trial he did not remember the bullying (at ). He did not associate the bully with the defendant. An independent observer, knowing all this, would not perceive a realistic possibility that the juror was not impartial (at ). There was no good reason to require that the juror be cross-examined (at ).