Section 138 deals with evidence obtained improperly or in contravention of Australian law. The respondents argued that Person 17 made the recording in Queensland, most likely using her phone, and must at some stage have communicated it to another person. The Court accepted that submission on the balance of probabilities. It said other possibilities existed, such as a telephone intercept or someone else gaining surreptitious access to Person 17's phone, but those possibilities were unlikely.
The Court therefore accepted that Person 17 made the recording in Queensland and at some point communicated it to at least one other person. The respondents said that communication engaged section 45 of the Invasion of Privacy Act 1971 (Qld). The appellant argued that the exception for a communication made in the course of legal proceedings applied. The Court found it convenient to assume in the respondents' favour that the exception did not apply and that Person 17 did commit the offence in section 45(1).
Even on that assumption, the Court still did not exclude the evidence. It worked through the factors in section 138(3). First, the recording's probative value, taken at its highest, lay in the middle range, which favoured admission. Secondly, the recording was the central evidence in the appellant's application, which also favoured admission.
The Court then considered the nature of the offence and the nature of the allegation raised by the recording. On one side, the hypothesised offence was an indictable privacy offence carrying a maximum penalty of 40 penalty units or two years imprisonment. On the other side, the allegation raised by the appellant was grave, namely that there had been a mistrial because of misconduct by Mr McKenzie in accessing privileged information. The Court said these considerations pulled in opposite directions, but the latter predominated, so this factor also favoured admission.
The Court accepted that, on the respondents' hypothesis, the communication was objectively very serious, deliberate, and inconsistent with Mr McKenzie's right to privacy under article 17 of the International Covenant on Civil and Political Rights. Those factors favoured exclusion. The Court found the factor about likely other proceedings neutral because there was no evidence on that point. It also found the factor about obtaining the evidence lawfully by other means neutral because it was unclear whether Person 17 could have given useful direct evidence.
After weighing all of those matters, the Court held that the desirability of admitting the recording outweighed the undesirability of admitting evidence obtained in that way. It therefore declined to exclude the recording under section 138. It added that if Person 17 had not shared the recording illegally, section 138 would not apply anyway. In either case, the result was the same: the recording and derivative versions were admissible.