Another aspect of B(SC12/2013) v R  NZSC 151 (19 December 2013) is its varieties of judicial interpretation of ss 40(3)(b) and 44 of the Evidence Act 2006. Of interest to us is the extent to which this aspect of the case is authority for anything.
Here the challenged evidence (held to be inadmissible) would have been that the complainant on an earlier occasion had invited a man to her house during the day to deal with a dead mouse, and when he was there she was wearing a nightie and a dressing gown. The man dealt with the mouse and left, but he felt that the complainant had been presenting an opportunity for a sexual encounter although she had done nothing overt in that regard.
What was this evidence intended to prove? If it just proved that the complainant invited people to her house to deal with mice, in this case it was hardly relevant because that was not a fact in issue: it was inadmissible, or at least not a miscarriage of justice for it to have been ruled inadmissible. William Young J favoured this approach to the issue of admissibility.
If the evidence was sought to be adduced to prove that the complainant had engineered a situation to have a sexual encounter with the defendant just like she had before in relation to the proposed witness, it would be evidence of her sexual experience with a person other than the defendant, so its admissibility would be governed by s 44(1) and (3). This was the approach favoured in the joint judgment of McGrath, Glazebrook and Arnold JJ.
William Young J didn't like that interpretation of the evidence or s 44 because the witness would not be testifying to an actual sexual experience, only to his impression of the complainant's motive for his visit. William Young J would not "read up" the word "experience" in s 44(1) to include things that didn't happen. It would have been different if the complainant had overtly suggested sexual activity on that occasion, but merely being dressed in a nightie and dressing gown wasn't enough.
Another interpretation of the evidence is that taken by the Chief Justice: the evidence was that the complainant had a propensity to create opportunities for sexual encounters at her home, which amounted to saying she had a reputation for doing that. This evidence of reputation had to be excluded because of s 44(2). It must be said that this is the least convincing interpretation of the proposed evidence.
At  William Young J cogently criticises Elias CJ's approach.
There was some obiter discussion of whether evidence of diary entries describing the complainant's sexual fantasies would be admissible. There was no such evidence in this case. The joint judgment would put this sort of evidence into the category of "experience" within the meaning of that term in s 44(1). William Young J would not, refusing to read up "experience" to include fantasies, and refusing to include, within the expression "with any person other than the defendant", the complainant herself.
When judges disagree over what are merely obiter dicta, what binds lower courts? When a case that directly raises the issue has to be decided, subsequent judicial reflection may favour the approach taken here by William Young J. But in the meantime greater weight should be given to the obiter dicta of the joint judgment here, simply because it is a majority opinion.
So, what is the ratio decidendi of the admissibility aspect of this case? All judges agreed that there was no miscarriage of justice arising from the evidence having been ruled inadmissible. Either it was irrelevant, or it was not of sufficient relevance to overcome the heightened relevance requirement of s 44(3), or it was inadmissible because it was reputation evidence. The majority applied the heightened relevance requirement, so the case is, from that perspective, a simple illustration of the application of s 44(1) and (3).
Legal propositions distilled from obiter dicta are not ratio decidendi, and neither are legal propositions not agreed to by a majority. There is therefore no wide ratio in this case, and it is only narrow authority on the admissibility of evidence of the same kind as that sought to be adduced here.
Perhaps you share my suspicion that the whole issue was argued under the wrong sections. The intended evidence was about the witness's opinion of what the complainant was thinking. The governing provision is s 24:
Here there was nothing that the witness "saw, heard, or otherwise perceived" other than the way the complainant was dressed. Her clothing did not require an explanation in the absence of any other overt conduct. There was no other conduct that the witness could point to that could require an explanation. Therefore the proposed opinion evidence was inadmissible.