In Tulloch (deceased) v Braybon  NSWSC 640, a witness was being cross-examined. He answered a question responsively. Then, he added some unresponsive material, and it was argued that this little unexpected and unresponsive addendum meant that it had become unfair to maintain client legal privilege over some associated subject matter.
Justice Brereton held that the conduct which gave rise to a prima facie implied waiver of the privilege had occurred in circumstances where the Court had been unable to comply with its obligation under s. 132 of the Evidence Act, 1995. Instead of saying that the cat was now out of the bag, and it had become unfair to maintain the privilege over the associated matter, the Court cured the unfairness by striking from the record the little addendum, thereby putting the cat back in the bag. The ‘it just popped out’ defence could be quite useful in a string of situations, where the Court has an obligation under s. 132 to warn witnesses of their rights (‘If it appears to the court that a witness or a party may have grounds for making an application or objection under a provision of this Part, the court must satisfy itself [that they] aware of the effect of that provision.’) What Justice Brereton said was:
‘7. …. it is well-established that inadvertent disclosure does not result in a waiver or loss of privilege, although this has typically happened when documents which are entitled to privilege have been produced inadvertently: see Hooker Corporation Limited v Darling Harbour Authority (1987) 9 NSWLR 538 and AWB Limited v Cole (2006) 152 FCR 382.
8 In this case, the first question set out above was unobjectionable and objection was not taken to it. The last part of the answer “I was in the courtroom, I heard all the questions and answers, yes” was responsive to that question. The witness approached that response, however, with material that was not directly responsive to the question and was not called for by it and which his counsel could not reasonably have been expected to anticipate. Although there had been some earlier references to privilege in the context of objections taken in the course of earlier cross-examination of this witness, those references were, if not sub silentio, at least in rather veiled speech. There was certainly no clear advice to the witness of his right to object to answering questions which would expose communications that had taken place between client and solicitor.
9 In those circumstances, it is relevant to bear in mind that the witness is entitled to have a warning or advice from the court in that respect, and indeed that the court is obliged to satisfy itself that the witness is aware of the effect of a provision that might entitle the witness to make an application or objection under a provision of Part 3.10 of the Act: see (NSW) Evidence Act, s132.
10 As the answer was given in the absence of such advice, and in circumstances where it is far from apparent that the witness knew or should have known that he was entitled to take such an objection, and where his counsel could not have anticipated the need to do so, I think I am bound to regard at least so much of the answer as was not directly responsive to the question and opened up privileged communications as having been given inadvertently.
11 In those circumstances I do not think it would be fair to hold that there had been a waiver of privilege as a result of that answer. At the same time, in circumstances where the claim for privilege is maintained, I do not think it would be fair to the plaintiff to allow the witness to rely on that answer.
12 Accordingly, in respect of the answer given, I reject the matter “Mr Hood and I didn’t discuss this line of questioning or whether he intended to ask Mr Tulloch or –”. Having rejected that, I disallow the subsequent question under objection.’