Navigating Subpoenas in Family Law: Lessons from Mertz & Mertz (No 3)

By Daniel Rod, Accredited Specialist, Family Law

In the recent decision of Mertz & Mertz (No 3) [2025] FedCFamC1F 144, Justice Berman delivered a concise yet masterful summary of the legal principles governing subpoenas, with a particular focus on relevance and the prohibition on fishing expeditions. For family law practitioners, this judgment is a must-read, offering clarity on the boundaries of document production in high-conflict litigation. Below, I explore how Justice Berman distilled decades of case law and legislative provisions into a practical framework, providing valuable guidance for lawyers navigating subpoenas.

The Case in Brief

Mertz & Mertz (No 3) arose in the context of a contentious family law dispute over parenting arrangements and property settlement. The wife sought leave to issue four subpoenas: two for the husband’s medical records (from MM Health Service and QQ Health Service), one for his clinical psychology notes (from Dr RR), and one for his employment records (from PP Pty Ltd). The husband objected, arguing that the subpoenas were irrelevant or amounted to fishing expeditions. Justice Berman refused leave for the employment records and the MM Health Service medical records but allowed the QQ Health Service records and psychology notes, subject to the husband’s first right of inspection and a seven-day objection period.

A Succinct Summary of the Law

Justice Berman’s judgment stands out for its eloquent synthesis of the law on subpoenas. He addressed three core questions: What is the purpose of a subpoena? When are documents relevant? And what constitutes a fishing expedition? His answers, grounded in case law and the Federal Circuit and Family Court of Australia (Family Law) Rules 2021 (Cth) (“the Rules”), provide a roadmap for practitioners.

The Purpose of Subpoenas

Justice Berman began with first principles, citing Lucas Industries Ltd v Hewitt (1978) 18 ALR 555 at 570:

"The purpose of the process of subpoena is to facilitate the proper administration of justice between parties."

This foundational statement, paired with the duty of full and frank disclosure under Chapter 6 of the Rules, underscores that subpoenas are not a free-for-all but a targeted tool to advance justice.

The Test of Relevance

The heart of the decision lies in the test of relevance. Justice Berman drew on Hatton v Attorney-General of the Commonwealth of Australia & Ors (2000) FLC 93-038 to outline when a subpoena may be set aside:

• If it lacks relevance,

• If it is oppressive,

• If it serves an improper purpose (e.g., discovery against a third party), or

• If it amounts to a fishing expedition.

He further refined this with the “on the cards” test from Martin & Martin and Anor (No) [2014] FamCA 232, where Cronin J held that it must be “on the cards” that the documents will materially assist the proceedings. This threshold, Justice Berman noted, citing Woley & Humboldt (No. 4) [2009] FamCA 546, does not require direct admissibility—documents need only “possibly throw light” on the issues. In family law, per Papadopoulos & Papadopoulos (No. 2) [2007] FamCA 1683, the bar may be even lower, provided the pursuit is genuine and not harassing.

The three-step process for subpoenas, derived from National Employers’ Mutual General Association v Waind and Hill [1978] 1 NSWLR 372 and affirmed in Hatton, was also highlighted:

1. Production: The witness brings the documents to court, and objections are resolved.

2. Inspection: The judge decides whether inspection is permitted, based on apparent relevance.

3. Use: The documents are admitted into evidence or used in examination.

Justice Berman emphasized, citing Dupont & Chief Commissioner of Police and Anor (2015) FLC 93-648, that a subpoena must serve a legitimate forensic purpose—otherwise, it is an abuse of process.

Fishing Expeditions Defined

On fishing expeditions, Justice Berman provided a clear and authoritative definition, referencing Hennessy v Wright (No. 2) (1980) 24 QBD 225 at 448:

"[A fishing expedition occurs where] the plaintiff wishes… to find out something of which he knows nothing now, which might enable him to make a case of which he has no knowledge at present."

He bolstered this with Andrew Garrett Wine Resorts & Anor v National Australia Bank Limited (No. 6) (2005) 92 SASR 419 at 428, where Gray J held that a “speculative possibility” is insufficient—there must be “real relevance” to the issues, not just an “outside chance” of something useful emerging. This distinction is critical for practitioners: subpoenas must be grounded in evidence, not hope.

Subpoenas vs. Discovery

Finally, Justice Berman addressed a common pitfall: using subpoenas as a substitute for discovery. Citing Macks v Tucker & Ors & QBE Insurance (Australia) Ltd (No. 4) [2007] SASC 255 at [49], he noted that if discovery is inadequate, the remedy is to seek further and better discovery—not to burden third parties with subpoenas. This reinforces the procedural integrity of the Rules, particularly rr 6.33 and 6.38, which govern objections and inspection rights.

Application to the Case

Justice Berman’s application of these principles was both practical and nuanced:

• Employment Records (PP Pty Ltd): The wife sought records to explore the husband’s departure from PP Pty Ltd, suspecting a link to his mental health or conduct. Justice Berman refused leave, finding the request overly broad and speculative. With existing orders requiring the husband to produce relevant employment documents, the subpoena was an impermissible attempt at discovery—an abuse of process.

• Medical Records: The subpoena to MM Health Service was rejected due to a lack of evidence suggesting relevant documents existed, deeming it a fishing expedition. Conversely, leave was granted for QQ Health Service and Dr RR’s notes, as the husband’s prior disclosure of suicidal ideation to Dr RR established a potential nexus to his parenting capacity—an issue in the proceedings.

Legislative Anchoring

The judgment naturally refers to the Family Law Rules 2021. Chapter 6 imposes the disclosure duty, while rr 6.33 and 6.38 provide the mechanism for objections and inspection.

Why This Matters for Lawyers

Justice Berman’s summary is a gift to practitioners. It distills complex precedent into a clear, actionable standard: subpoenas must be relevant, purposeful, and evidence-based. For family law lawyers, where personal records are often at stake, this decision reinforces the need for precision. Before issuing a subpoena, ask: Is it “on the cards” that these documents will assist? Is there a legitimate forensic purpose? Or am I fishing?

Conclusion

Mertz & Mertz (No 3) is a testament to judicial clarity. Justice Berman’s eloquent articulation of relevance and fishing expeditions, backed by authoritative case law and the Family Law Rules, offers a blueprint for ethical and effective litigation. For lawyers, it’s a call to wield subpoenas with care—ensuring they serve justice, not speculation.