The Supreme Court of New Zealand has decided the jury vetting case (see blogs for 14 April 2008 and 29 July 2008): Gordon-Smith v R  NZSC 20 (23 March 2009).
The majority (McGrath J dissenting) upheld the Court of Appeal majority decision:
"22. ... the Crown should disclose any previous convictions of a potential juror known to it, if the previous conviction gives rise to a real risk that the juror might be prejudiced against the accused or in favour of the Crown. Disclosure should not otherwise be made. By this means the interests of accused persons are reconciled with the legitimate privacy and security concerns of jurors. The non-disclosure of a previous conviction which does not give rise to a real risk of prejudice cannot be said to jeopardise the accused's right to a fair trial."
McGrath J's dissent, echoing the position taken by Robertson J in the Court of Appeal, led him to conclude:
"87. ... the Crown has to make disclosure within a reasonable time prior to trial of all information concerning convictions of those on the panel whenever that information is in the Crown's possession and a juror with a prior conviction is not to be challenged by the Crown. The ... Crown must similarly disclose other information it receives from the police which may indicate a juror is possibly biased."
The dissent reasoned that, since the accused's right to a fair trial is absolute (84, citing R v Condon  1 NZLR 300 (SC), at para 77), and as there is no need to supplement the extensive legislative provisions recently introduced to protect jurors' privacy interests, and as opinions may vary on the significance of previous convictions in relation to potential juror bias (82), and as a well-informed observer would have reasonable grounds for apprehending that a jury may not be impartial when selected in the context of an imbalance of information as between Crown and defence, all information available to the prosecutor should be shared with the defence (86, 87). McGrath J would also have required Crown challenges to be exercised in a principled way in accordance with instructions that would need to be promulgated.
The majority downplayed the risk of unfairness, calling it "entirely speculative" (17). The recent legislation bolstering jurors' privacy interests was taken to be a lead the Court should follow (19), and
"20. With these points in mind we do not consider it is necessary or desirable to go as far as Robertson J and require all information to be made available. That would unreasonably impact on jurors' legitimate concerns for their privacy and security, and for no sufficient reason. ... ."
The majority would not require disclosure of any information other than convictions.
In other words, the Crown can decide when a previous conviction gives rise to a real risk of bias such that the defence would wish to challenge the juror.
Many readers of this decision will be sceptical of the majority judgment. Sarcastic readers (for alas, some there will be) will think the Crown may as well exercise all the defence challenges.