I am not saying that updating one’s textbooks is a wonderful hobby.
But it can bring to your attention cases that, although currently suppressed, are of great interest to lawyers.
One such opened on my screen this morning. Because of its suppression order, and the possibility that the order may still be in effect (the case is not currently freely available online), I dare not speak its name. Nor will I say anything about its alleged facts, the charge(s), or anything else that could with any seriousness be regarded as a breach of the order.
The legal point is about how appellate courts are to interpret s 232(2)(c) of the Criminal Procedure Act 2011, concerning certain types of appeals against conviction. Specifically, and in historical context, has the removal of the proviso affected the meaning of “miscarriage of justice”? Under the proviso, an appeal could be dismissed if, notwithstanding the existence of a miscarriage of justice, it was not a “substantial” miscarriage of justice.
The new approach, under the current legislation as interpreted by the Court in this case is, if there has been an error relating to the trial that is more than inconsequential or immaterial, ask (1) whether the error has resulted in a real risk that the outcome of the trial was affected adversely to the appellant; and if there is that risk, ask (2) whether on the material available to the appellate court the court can be sure that the appellant is guilty, taking a conservative approach to this assessment in the light of the disadvantages that the appeal court has.
Has the Supreme Court read-in a proviso? On the plain words of the legislation, which are admirable for their simplicity and not in need of modification, there is no proviso. The appellate judges just assess a risk, and do not have to reach a verdict. But the approach set out by the Supreme Court comes down to: if there is a real risk that an error affected the result of the trial adversely to the appellant, allow the appeal “provided that” (my words) the appeal can be dismissed if the appeal court finds the appellant guilty.
I suggest that it is important to recognise that an appellate court is not permitted to readily accept that guilt is proved on the record, but must be very careful and only dismiss appeals where guilt is obvious.
And to those who say, "But Don, if the answer to question (1) is yes, how can the answer to (2) also be yes?" I can only reply, I feel your pain.
The Court has turned a statutory question which addresses how the fact-finder at trial could have been affected into a question about the appeal court's verdict.
To what extent was there a problem of statutory interpretation here? To what extent should a court rely on the expectations of people who work in the background in the preparation of legislation (and who write explanatory notes to bills), to ascertain the meaning of an enactment? There are statutory directions about how legislation is to be interpreted (we have the Interpretation Act 1999 and the yet to come into force Legislation Act 2019 update: it was fully in force, except for s 148, on 28 October 2021) and these point to using the text and purpose of the enactment - and here we would look at the purpose provision of the Criminal Procedure Act 2011, s 3, which is simply "to set out the procedure for the conduct of criminal proceedings". On the face of the legislation (s 232 of the Criminal Procedure Act 2011) there is no interpretive difficulty.
On a plain reading, s 232 reproduces the approach to appeals that had been accepted in R v McI  1 NZLR 696 (CA), as described in Matenga (below) at -. The focus in McI was on what the jury would have done, and the appellate court was not required to come to its own verdict. This raises the question whether the drafters of the legislation were thinking of the law as stated in McI when they said that no change was intended. 
It is only when one tries to fit the law as modified in Matenga into the new provision - in accordance with the prediction of the legislation drafters that there would be "no change to the core principles underlying the courts' current approach" to these appeals - that some interpretive stretching is needed. What the core principles underlying the courts' approach were is indeed itself an interpretive question.
I have commented on a case concerning the relevance of the old law to new law on appeals, Baini v The Queen  HCA 59 at -. (In the update to that comment, I have referred to the present case, but with its citation only.)
In the present appeal the interpretive point was obiter, because the Court found that an evidential ruling had rendered the trial unfair, and that therefore the conviction(s) had to be quashed without further consideration of the evidence. Naturally, the Court would want to decide at the earliest opportunity how s 232(2)(c) works, and it did seek submissions on the point, but as it turned out there was no argument because counsel agreed that there had been no change in the law. Normally, failure to take an issue, and the obiter nature of the decision, would make a case weak authority, but obviously here the authoritative decision has been made.
Still, one mustn’t mope. Moving forward with this: the position really isn’t all that bad. The decision is that if an appeal court finds that there was an error at trial that created a real risk of an adverse outcome for the defendant, the appeal against conviction must be allowed unless the appeal court can be sure, on the evidence properly admissible, that the appellant’s conviction was correct. This approach is that which had been clearly set out in R v Matenga  NZSC 18 (where inadmissible evidence had been adduced by the prosecution and the Supreme Court could not be satisfied that the admissible evidence proved guilt). In Matenga the Court noted at  that where a case turns on the honesty or reliability of witnesses the appeal court is unlikely to be able to be sure of the defendant’s guilt, and this was the position in Matenga (at ). Where inadmissible evidence was relied on at trial, the appellate approach is as stated in Lundy v R  NZSC 152 at , and see Ellis v R  NZSC 77 at - (leave to adduce evidence refused).
I think it would be sensible to treat the first question as whether there could have been the requisite risk, and then, if there could have been, ask whether there was such a risk, and to answer that by reference to the appeal court's verdict.
Interestingly, in refusing leave to adduce evidence in the Ellis appeal, the Court rejected a Crown submission that on appeal the Court would essentially be acting as the "final trier of fact" (at ), and stated that it would be engaged in "determining whether a miscarriage of justice occurred at the appellant's trial. That is a quintessentially appellate task." This view pushes any thought of the proviso (the old law applies to this appeal) well into the background.
 Mistakes can occur in the explanatory notes and official commentaries. In the Select Committee Report on the Bill the Commentary on the appeal provisions contains a misunderstanding of the significance of the word "rehearing" (see my note on 2 December 2019). Anyway, the Commentary was added when the original draft of the relevant clause (236) was revised by removing a reference to rehearing, and by defining substantial miscarriage of justice to include reference to trial unfairness, so that after later removal of the word "substantial" by the Committee of the Whole House, the clause was brought into a form mirrored in what is now s 232. I recently found my submissions to the Select Committee (17 February 2011) in which I raised concerns about the appeal proposals, including an objection to the use of the expression "substantial miscarriage of justice". The then Chief Justice wrote to the Committee a few days later (25 February), also submitting that the word "substantial" should be omitted. The fact that the Bill was called the Criminal Procedure (Reform and Modernisation) Bill does suggest that it shouldn't be assumed that its provisions do not reform the law. And you can see from the linked documents that the Commentary's assertion of no change precedes the deletion of the word "substantive" at the last Committee stage. However, the same assertion is repeated in the Supplementary Order Paper (SOP No 281) which deleted the word "substantial": "The amendment simplifies but does not alter the test for allowing an appeal against conviction." While that may be partly true, you might still wonder why, when the wording was under consideration, no effort was made to expressly give any verdict determining ability to the appellate court by including an equivalent to what the Court has in the present case formulated as the second question.