In a decision published in May 2020, Justice Logan of the Federal Court of Australia provided a timely reminder of the implied undertaking as to evidence, as well as some of its exceptions. In Sinnott v Chief of Defence Force [2020] FCA 642 (Sinnott), his Honour confirmed that receiving evidence in litigation carries with it an implied undertaking not to use that evidence for a purpose other than the litigation, but nevertheless granted the Chief of Defence Force (CDF) leave to use evidence received in the course of the case for certain other public interest purposes.

What is the implied undertaking?

The implied undertaking as to evidence has its origins in the United Kingdom case of Harman v Home Department State Secretary [1983] 1 AC 280, which is why it is occasionally referred to as the Harman obligation or undertaking. In Australia, the leading statement of the principle comes from the High Court's decision in Hearne v Street (2008) 235 CLR 125. In that case, Justices Hayne, Heydon and Crennan JJ described the principle in the following way:

[96] Where one party to 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 types of material disclosed to which this principle applies include documents inspected after discovery, answers to interrogatories, documents produced on subpoena, documents produced for the purposes of taxation of costs, documents produced pursuant to a direction from an arbitrator, documents seized pursuant to an Anton Piller order, witness statements served pursuant to a judicial direction and affidavits.

In short, if you receive evidence in litigation from another party, you are not to use it for any other purpose other than for the litigation itself, unless you are given the court's leave to do so. The undertaking is implied because the recipient of the evidence is not required to give an express commitment not to use the evidence for another purpose; instead, it is an unspoken commitment that is given on receipt of evidence by one party from another.

Exceptions to the implied undertaking

What, then, are the circumstances in which a court will grant leave? In Sinnott, Logan J confirmed that it will depend on the facts of the case and whether there is a legitimate public interest in the recipient's proposed wider use of the evidence. Some examples of a legitimate public interest are:

• Where the recipient of the evidence is charged with investigating possible criminal conduct, and the evidence suggests criminal conduct of that kind: Australian Trade Commission v McMahon (1997) 73 FCR 211.
• Where a statutory provision means the implied undertaking does not apply: Deputy Commissioner of Taxation v Rennie Produce (Aust) Pty (in liq) [2018] FCAFC 38.
• Where the recipient is charged with investigating conduct that may warrant disciplinary action, and the evidence suggests conduct of that kind.

It was these latter circumstances that applied to the Sinnott case. It is useful to briefly explore the facts of the case to understand when a court may grant leave for a party to be released from the implied undertaking.

What were the facts in Sinnott?

Ms Sinnott, a former member of the Royal Australian Air Force (RAAF), commenced proceedings against the CDF in December 2019 in respect of a decision to reject her re enlistment in the RAAF. Ms Sinnott engaged Mr Hooper as her solicitor for the case. In addition to being a solicitor in private practice, Mr Hooper was, at the same time, a specialist reserve legal officer in the RAAF. On the same day the case was commenced, Mr Hooper filed an affidavit deposed by himself, which exhibited an extract from the Defence Health Manual, marked "For Official Use Only". In the affidavit, Mr Hooper stated that he had access, in his capacity as a reserve legal officer, to various Australian Defence Force (ADF) policies and rules via the Defence Restricted Network.

The CDF subsequently applied to Logan J to use Mr Hooper's affidavit for the following purposes beyond the litigation:

• to provide a copy of the affidavit to appropriate ADF members for the purpose of investigating and considering any security, disciplinary or administrative issues that might arise on the content of the affidavit; and
• to provide a copy of the affidavit to the Queensland Legal Services Commissioner (QLSC) for the purpose of any investigation or consideration of issues that might arise from the content of the affidavit.

In support of that application, evidence was provided by the CDF that Mr Hooper, in his capacity as a reserve legal officer, cannot represent individual members of the ADF in court proceedings of the kind that he was for Ms Sinnott and, although there was no express rule preventing him from doing so in a private capacity, he was subject to normal professional ethical obligations. Further, the CDF provided evidence that he had formed a belief that there had potentially been unauthorised access to documents on the Defence Restricted Network and unauthorised disclosure of a confidential Defence document.

Justice Logan found that the CDF had 'a very real and legitimate interest' in the wider use of Mr Hooper's affidavit 'in terms of reflective inquiry and related policy formulation concerning the interface between military legal and civilian legal practice'. His Honour held that this reason, in itself, was sufficient to establish special circumstances for the granting of leave. In addition, his Honour found that there may also be a use in relation to the proposed referral to the QLSC. In making those findings, his Honour accepted Mr Hooper's argument that the extract from the Defence Health Manual was directly relevant to the case, but held that mere relevance was no answer.

Key points to take from Sinnott

Sinnott is a useful reminder that evidence received in the course of litigation is not to be used for another purpose, unless a court grants leave for that to occur. 

Sinnott also provides guidance on the range of circumstances in which a court may consider that there is a legitimate public interest reason to grant leave to a party to use evidence for another purpose. This would seem most likely to apply where the party seeking leave is involved in public administration or law enforcement.

However, it is not the case that, without the grant of the court's leave, the implied undertaking cannot set in train a line of inquiry or investigation that leads to obtaining the same, or similar, evidence by other means. So much is recognised by Logan J in Sinnott. In the judgment, his Honour acknowledged an argument made by Mr Hooper that any investigation that the ADF may wish to undertake in relation to his accessing of the Defence Restricted Network for the retrieval of the extract of the Defence Health Manual could readily be done by reference to the material already under the control of the ADF, such as access logs and other information. While his Honour did not accept that this meant that there was not a legitimate reason for leave to be granted, this passage of the judgment recognises that, even without a court's leave, evidence filed in litigation can set in train a line of inquiry or investigation with a view to obtaining the same, or similar evidence, by other means.