If the warning to which par (a) is directed is a warning that it is generally unsafe to convict for any sexual offence on the uncorroborated evidence of the alleged victim (or, to put the warning another way, that it is unsafe to convict on the uncorroborated evidence of the alleged victim of the particular sexual offence charged because evidence of that kind has been shown by experience to be especially liable to fabrication), par (a) does not affect the requirement to warn about other perceptible risks of miscarriage of justice. A warning may be required because of the circumstances of the case other than, albeit in conjunction with, the sexual character of the issues which the alleged victim's evidence is tendered to prove. Paragraph (a) leaves that situation unaffected.
Furthermore, what par (a) abolishes is the requirement to give a warning, not a judge's discretion to comment on the circumstances of the case. No longer may the judge tell the jury that it is dangerous to convict in the circumstances described in par (a) because the experience of the courts has shown it to be so, but the judge may invite the jury in sexual cases (as is done in other criminal cases) to make their own evaluation of the alleged victim's evidence in the light of common human experience. By force of par (a) alleged victims of sexual offences no longer form a class of suspect witnesses, but neither do they form a class of especially trustworthy witnesses. Their evidence is subject to comment on credibility in the same way as the evidence of alleged victims in other criminal cases, but to comment only. Perhaps it should be added that the judge's discretion to comment should not be exercised so as to convey to the jury, whether by phrase, gesture or intonation, a caution about the general reliability of the evidence of alleged victims of sexual offences which is tantamount to the warning the requirement for which par (a) eliminates.
Paragraph (b) is a unique provision. Its first limb is clearly intended to supplement par (a) by prohibiting the giving of a warning which, the legislature obviously feared, judges might have continued to give despite the abolition of the requirement to give it. Its second limb seems to reflect a misconception of the effect of par (a). Once par (a) abolishes the requirement that jurors be warned that the evidence of alleged victims of sexual offences is generally to be treated with suspicion, no particular set of circumstances could justify the judge's directing jurors that all such evidence is treated with suspicion. If par (a) abrogates the rule which reflects curial experience of the need for caution in evaluating the evidence of alleged victims of sexual offences because of the risk of fabrication, then there is no particular set of circumstances which can justify the trial judge in giving the jury a warning based upon general experience. It would make no sense to treat the warning which par (b) permits - a warning based upon particular circumstances - as being restricted to the same kind of warning as that to which par (a) refers - a warning based upon general experience.
That is to say, unlike par (a), par (b) must relate, not so much to a warning of the general unsafety of convicting on the uncorroborated evidence of alleged victims of sexual offences, as to a warning which a trial judge might consider giving on account of the particular circumstances of the case. That is because par (b) directs the judge to find his justification for giving 'such a warning ... in the circumstances'. If the warning which may be given pursuant to par (b) cannot be the warning referred to in par (a), the phrase in par (b) 'a warning ... of the kind described in paragraph (a)' must be taken to mean any warning that it is unsafe in the circumstances of the particular case to convict on the uncorroborated evidence of the particular alleged victim.
Construing par (b) in that way, it prohibits in any case of a sexual offence the giving of any warning that it is unsafe to convict the accused on the uncorroborated evidence of the alleged victim unless the judge is satisfied that the particular warning is justified in the circumstances. The judge cannot be so satisfied if there is nothing in the case to require a warning other than the circumstance that proof of the offence rests on the uncorroborated evidence of the alleged victim. So construed, par (b) first shuts the door on all warnings that it is unsafe to convict an accused on the uncorroborated evidence of an alleged victim, and then reopens it to such warnings where the particular circumstances of the case provide a justification. This construction of the section is somewhat artificial, but it is essential to avoid absurdity. If the words 'of the kind described in paragraph (a)' were to be construed so that the warnings referred to by the respective paragraphs were the same, par (a) would comprehend a warning which might be 'justified in the circumstances'. Such a construction would accord to par (a) a wider operation than is accorded to that provision in other States and destroy the protection afforded in appropriate cases by the requirement to give a warning unrelated to the suspicion attaching to the evidence of alleged victims of sexual offences.
Paragraph (b) thus comprehends more kinds of warnings than the kind of warning to which par (a) refers. Although a warning can be given only if the judge is satisfied that the warning is justified in the circumstances - and therefore must not be given unless, on a view of the facts reasonably open to the jury, there is an occasion for giving a warning - justification may be found in any requirement of a rule of law or practice which might apply in the circumstances other than the requirement to which par (a) refers. If, on a view of the facts reasonably open to the jury, a rule of law or practice requires a warning to be given, not being a warning of the kind to which par (a) refers, the rule must be followed. The rule is itself justification for giving the warning it requires (87 - 89).