Many interesting issues have arisen in the current litigation involving former Attorney-General, Christian Porter.
The underlying story is of course the one that gets the most headlines. But there are important lessons here for anyone who is regularly involved in litigation, especially where a party wants to utilise documents it has previously obtained in a separate litigation.
In short, anyone who wants to go down that path should think twice (or more) about doing so.
The principle was clearly stated by the High Court in Hearne v Street (2008) 235 CLR 125, where it said, "when one party to the litigation is compelled, either by reason of a rule of court, or by reason of a specific order of the court, or otherwise, to disclose documents or information, the party obtaining the disclosure cannot, without the leave of the court, use it for any purpose other than that for which it was given unless it is received into evidence".
The principle applies to numerous documents such as those inspected after discovery, or documents produced on subpoena, or witness statements served pursuant to a judicial direction.
Whether or not the principle applies to pleadings filed in court is far more contentious, and was discussed at some length in Porter v ABC.  FCA 863. The Federal Court noted that there have been judgments either way on that point over the years, as the courts have tried to grapple with just how narrowly the concept should be applied.
The principle is sometimes referred to as the Harman Undertaking, which drew its name from a case in the House of Lords in 1983. However, it is more accurate to describe the rule as being a positive obligation on litigants, rather than just an undertaking.
To increase the stakes even more, the implied undertaking not to use documents obtained in this way is made to the Court, not to the party who produced the documents. Therefore, only the Court can release a party from its Harman undertaking, which in turn means that a breach of the obligation can be contempt of Court.
And as various unfortunates can tell you, wandering – or more accurately, blundering - down a path which may lead you to being in contempt of Court is not a course to be taken lightly.
How does it work?
Like the current argument in Porter, the facts of Hearne v Street arose from a high-profile event. Residents who lived adjacent to Luna Park brought an action against Luna Park's owners, essentially claiming that the squeals of patrons, and various other noises emanating from the Park, caused the residents 'a nuisance'. This was a hot topic at the time and attracted a lot of media attention.
Luna Park sought the support of the NSW government, requesting legislation be introduced to protect them from this kind of noise complaint.
The residents relied on 15 affidavits in support of the claim. These affidavits had not yet been 'read' in the proceedings and therefore did not yet form part of the publicly available court record.
The owners of Luna Park provided several of these affidavits to the Daily Telegraph, which duly published them. Solicitors for the residents then requested an undertaking not to release 'unread' affidavits to the media or any other person not connected to the proceedings. Luna Park's solicitor gave the undertaking, and an apology.
Nevertheless, sometime later, a director of Luna Park provided a section of one of the unread affidavits to the NSW Minister for Tourism, Sport and Recreation, in a lobbying attempt. This constituted a clear breach of the undertaking, and the residents commenced proceedings for contempt of court which went all the way to the High Court.
The High Court unanimously found for the residents, holding that the "implied undertaking is an obligation of substantive law". There is nothing voluntary about the "undertaking" and it should be instead expressed as an implied obligation not to make improper use of such documents.
All litigants – parties and lawyers alike – have experienced that "gotcha" moment when your opponent's discovery process yields a crucial document which you may not have known for sure even existed.
But next time it happens to you, just remember to channel your excitement strictly into the case at hand. If that document never goes into evidence, don't even think about using it for some other purpose – no matter how tempting it may be.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.