What is inadvertent disclosure?
Rule 31 of the Australian Solicitors Conduct Rules 2012 deals with what we do when we receive confidential but inadvertently disclosed materials.
Inadvertent disclosure occurs where we receive material which we know or reasonably suspect to be confidential and we are aware that the material has been disclosed inadvertently. If these circumstances exist then upon receipt you must not use the material, we must return, destroy or delete the material immediately and should notify the sender (whether a solicitor or otherwise) of the steps we have taken to prevent inappropriate use of the material.
On occasions, we may only become aware that the material is confidential and has been disclosed inadvertently after we have commenced reviewing in whole or in part the document or material received. In those circumstances, we should notify the sender immediately, not review further the material and take steps to return or destroy the material.
If after receipt of the confidential but an inadvertently disclosed document we are instructed by our client to review it, we must refuse to do so.
The High Court in Expense Reduction Analysis Group Pty Ltd and Armstrong Strategic Management and Marketing Pty Ltd (2013) 250 CLR 303, 325 noted:
The position of solicitors who are in receipt of privileged documents has another dimension. Rule 31 of the Australian Solicitors Conduct Rules, which were adopted by the Law Council of Australia, deals with the duty of a solicitor to return material, which is known or reasonably suspected to be confidential, where a solicitor is aware that its disclosure was inadvertent. It involves notifying the other solicitor of the disclosures and returning that material. The rule has been adopted in Queensland and South Australia and the Law Society of New South Wales presently proposes to adopt it.
Such rule should not be necessary. In the not too distant past it was understood that action in this way obviates unnecessary and costly interlocutory applications. It permits a prompt return to the status quo and there by avoids complications which may arise in the making of orders for the rectification of the mistake and the return of documents.
This approach is important in a number of respects. One effect is that it promotes conduct which will assist the court to facilitate the ethical obligations of legal practitioners supporting the objections of the proper administration of justice. 
This was a unanimous decision of the Court. The reference in the decision to the CPA is a reference to the Civil Procedure Act 2005 (NSW). It should be noted that the Uniform Civil Procedures Rules 1999 (UCPR) also creates a positive duty upon a party and it’s legal representatives to facilitate the UCPR’s purposes. One of the purposes is to “facilitate the just and expeditious resolution of the real issues in civil proceedings at a minimum expense”.
Senior Ethics Solicitor
2 April 2015