Surveillance Devices Law
Equity - A Quick Description
Certain rules of law based on case law and not statutory law have relevance to surveillance operations. These rules come under the heading of a body of law called Equity. Firstly, a brief introduction. Equity is a case law system akin to common law, but founded on principles of fair play and the upholding of promises. It operates to prevent injustice when common law or statutes would operate unjustly through strict application of their rules. It features specific rules designed largely with this end in mind, one of them being a general duty of confidentiality.
It is well established that an equitable duty of confidentiality exists. It impinges upon the work of a circumstance investigator, or anyone else who takes evidence overtly in interviews, verbal enquiries or document discovery. It restrains the inquirer from passing on information obtained in circumstances that imply confidentiality to any party without the authorisation of those it came from. That of course is only to compel relevant professionals to do exactly what they already do.
It operates very differently, however, in regard to surveillance investigators because all of the information they obtain is obtained without consent and where evidence of a wrong is discovered, the revelation of it operates to the subject’s harm. The following paragraphs explain and investigate this principle further.
This aspect of the law was recognised by the High Court in ABC v Lenah Game Meats. Trespassers hid cameras inside an abattoir’s premises and took pictures of the processes of possum slaughtering, which were later broadcast on television. The court described a duty to treat private information with confidentiality where it is either provided in circumstances of trust and confidence or obtained illegally, improperly or surreptitiously. Chief Justice Gleeson stated:
... the principle of good faith upon which equity acts to protect information imparted in confidence may also be invoked to ‘restrain the publication of confidential information improperly or surreptitiously obtained’. The nature of the information must be such that it is capable of being regarded as confidential. A photographic image, illegally or improperly or surreptitiously obtained, where what is depicted is private, may constitute confidential information...
If the activities filmed were private, then the law of breach of confidence is adequate to cover the case... There would be an obligation of confidence upon the persons who obtained [images and sounds of private activities], and upon those into whose possession they came, if they knew, or ought to have known, the manner in which they were obtained...
What is important to be aware of here is that surreptitiously, though lawfully, obtained imagery of private activities are included as confidential information, even where there is no exercise of trust. This stands clearly in the way of reporting on surveillance and pretext-based enquiries, as long as the report is to go to a party which the subject has not authorised.
To elucidate, let us examine some antecedent cases. Considering this principle in the context of sensitive government information concerning military and secret intelligence matters to be published in newspapers, Mason J in the leading case of Commonwealth v John Fairfax & Sons looked into how the release of the given subject matter would damage the aggrieved party (the Federal government), and whether a duty of confidentiality arises from that:
The court will not prevent the publication of information which merely throws light on the past workings of government,.. so long as it does not prejudice the community in other respects... There will be cases in which the conflicting considerations will be finely balanced, where it is difficult to decide whether the public's interest in knowing and in expressing its opinion, outweighs the need to protect confidentiality.
Support for this approach is to be found in Attorney-General v. Jonathan Cape Ltd. (1976) QB 752 [pp770-771], where the Court refused to grant an injunction to restrain publication of the diaries of... [a person. It was said that]: "The Attorney-General must show (a) that such publication would be a breach of confidence; (b) that the public interest requires that the publication be restrained, and (c) that there are no other facts of the public interest contradictory of and more compelling than that relied upon. Moreover, the court, when asked to restrain such a publication, must closely examine the extent to which relief is necessary to ensure that restrictions are not imposed beyond the strict requirement of public need." 
ORDER FOR FULL TEXT.
 Australian Broadcasting Corporation v Lenah Game Meats Pty Ltd (2001) 208 CLR 199, , . Quote uncited from Lord Ashburton v Pape (1913) 2 Ch 469, 475.
 Commonwealth v John Fairfax & Sons ("Defence Papers case")  HCA 44; (1980) 147 CLR 39, -.
 Francome v Mirror Group Newspapers Ltd  2 All ER 408
 Kettles and Gas Appliances Ltd v Anthony Hordern and Sons Ltd (1934) 35 SR (NSW) 108.
 Meagher R, Heydon D & Leeming, M, Meagher, Gummow and Lehane’s Equity: Doctrines and Remedies, Fourth Edition, Lexis Nexis Butterworth’s, Sydney, 2002, [3-120].