A colleague put me on to a recent case summary from the VGSO about a pre-trial decision of the County Court in DPP v KW. I haven't been able to find an online copy of the ruling, so all I can refer to is the summary above.
It seems the police were investigating an allegation of attempting to procure sexual penetration by threat or force, contrary to Crimes Act 1958 s 57.
The complainant was apparently provided a recording device and left alone to telephone the accused. (This is sometimes called a 'pretext conversation', so called because the complainant telephones the suspect on the pretext of discussing the alleged offence, when it is really being recorded by the police as an investigative tool. Police now more frequently resort to such conversations in an attempt to obtain confessions and admissions, particularly in sexual investigations.)
The complainant recorded the conversation. No police were present. There was no warrant issued under the Surveillance Devices Act 1999. Section 6 of that act provides:
6. Regulation of installation, use and maintenance of listening devices
(1) Subject to subsection (2), a person must not knowingly install, use or maintain a listening device to overhear, record, monitor or listen to a private conversation to which the person is not a party, without the express or implied consent of each party to the conversation.
Penalty: In the case of a natural person, level 7 imprisonment (2 years maximum) or a level 7 fine (240 penalty units maximum) or both; In the case of a body corporate, 1200 penalty units.
(2) Subsection (1) does not apply to—
(a) the installation, use or maintenance of a listening device in accordance with a warrant, emergency authorisation, corresponding warrant or corresponding emergency authorisation; or
(b) the installation, use or maintenance of a listening device in accordance with a law of the Commonwealth; or
(c) the use of a listening device by a law enforcement officer to monitor or record a private conversation to which he or she is not a party if—
(i) at least one party to the conversation consents to the monitoring or recording; and
(ii) the law enforcement officer is acting in the course of his or her duty; and
(iii) the law enforcement officer reasonably believes that it is necessary to monitor or record the conversation for the protection of any person's safety.
The County Court considered the police involvement and the effect of Charter s 13(a) (right to privacy), and concluded that the police knowingly used a listening device to record a private conversation. (I'm not sure why s 6(2)(c) didn't apply in the circumstances.)
Despite this, the Court concluded discretionary exclusion of the recording under Evidence Act 2008 s 138 was not required.
It will be interesting to see what comes of this decision. Because it's a County Court case — and a pre-trial ruling at that — strictly speaking, it creates no precedent: Whittaker v Delmina Pty Ltd  VSC 175 at  - ; Valentine v Eid (1992) 27 NSWLR 615.
But it would be foolhardy to simply ignore it.
There are a few appellate cases considering pretext conversations.
A critical question is if the complainant is acting as an agent of the police, and if the pretext conversation is an attempt to subvert or avoid the operation of and protection provided by s 464H, such as considered by the High Court in R v Swaffield; Pavic v The Queen (1997) 192 CLR 159.
In R v East (2005) 154 A Crim R 1, the NT Supreme Court considered the meaning of private conversation. Applying Victorian authority, the court held that a private conversation is determined by considering the objective circumstances surrounding the conversation, rather than the subjective intent of an individual involved in the conversation. So, if one party to the conversation wants or indicates they want the conversation to be overhead or recorded, it isn't a private conversation.
In R v Workman (2004) 60 NSWLR 471 a sexual assault allegedly occurred in Sydney. The complaint was made after the victim moved to Queensland, and so investigated by Queensland police. A pretext conversation occurred between the victim in Queensland and the defendant in New South Wales, recorded by a device placed next to a speaker phone. In Queensland, recording a conversation is not illegal if the person using a listening device is a party to the conversation. This is also the case in Victoria. However, in NSW, this was illegal under the Listening Devices Act 1984 (NSW) s 5(1). Despite this, the tape recording was properly received into evidence.
There are more cases, often turning on questions of entrapment or involuntariness. One risk for the police is if a court concludes the process was surreptitious or some attempt at circumventing legislative protections for a suspect. In R v Dewhirst (2001) 122 A Crim R 403 the Supreme Court excluded recorded conversation between an undercover police officer in the police cells and a suspect: not because of the covert nature of the questioning, but rather because it was planned to elicit further information from the accused without legislative protection and regardless of what happened during a previous formal interview. (It turned out that he exercised his right to silence, which probably only aggravated the decision to question him in the cells.)
The Court concluded with reference to an earlier case:
The courts, however, will be vigilant to ensure that the legislative safeguards accorded to suspects are not circumvented as a matter of mere investigative convenience or expediency: R v Roba  VSC 96 at .
Though the facts there were different — and it wasn't really a pretext conversation — it neatly encapsulates the concerns of the courts in such cases. Seemingly that didn't occur in KW, but pretext conversations will nearly always be subject to close scrutiny for such vices.