A witness's privilege against self-incrimination
Cases of alleged domestic violence are among those where a complainant may wish to deny the truth of her earlier complaint or of her evidence in pre-trial proceedings. She would then be admitting wasting police time by making a false complaint, or perjury. Will she be able to claim a privilege against self-incrimination so that she is not forced to give evidence incriminating the defendant at his trial?
This depends, as the New Zealand Supreme Court held in DK Singh v R  NZSC 161 (17 December 2010), on how "likely" (s 60(1)(b) of the Evidence Act 2006[NZ]) it is that provision of the information sought would be used to incriminate the witness, that is, on whether there is a "real and appreciable" – as opposed to a "merely imaginary and fanciful" risk of incrimination (Singh at , citing Cockburn CJ in R v Boyes (1861) 1 B & S 311 at 330, 121 ER 730 (KB) at 738). In the circumstances of Singh the Court assessed this likelihood as sufficiently low to justify denial of the privilege.
The Court added that the privilege belongs to the witness, and it is not open to the appellant to make the claim on her behalf if she had waived it, applying R v Kingslake (1870) 11 Cox CC 499 (QB) and noting the consistency with s 60(4)(b) of the Evidence Act 2006.
Hostility and prior consistent statements
In the trial in this case the Crown had obtained a ruling that the witness was hostile, so that by cross-examination it was revealed that she had previously stated that the alleged offences had occurred. The defence then sought to have some of her prior consistent (that is, consistent with her denials of the offending) statements admitted under s 35 of the Evidence Act. But on the facts here the Court assessed those statements as not having sufficient probative value to make them "necessary to respond" to the Crown's challenge to the witness's accuracy or veracity, and held that their selective nature would make admitting them unfair to the prosecution and would require a time-wasting diversion (s 8 Evidence Act).
The appellant's fundamental argument was that the trial had been unfair. This is dealt with at the end of the judgment [59-61]. This argument was put on the grounds (as I would paraphrase on the basis of my analysis of trial fairness) that the jury would not have assessed the evidence impartially because the witness's credibility had been improperly undermined. It seems from the judgment that the unfairness argument was based on the jury not having been given a direction that they might consider that her clumsy attempts to deny that the offending had occurred were due to her fear of being prosecuted for perjury. That is, there was a real risk that the jury's assessment of the value of her evidence was not an impartial assessment because all relevant considerations may not have been taken into account.
The Court concluded that the jury had been given sufficient information to be able properly to assess the witness's credibility. A fear of prosecution would not have affected the way she gave evidence.