When you're involved in a legal case—especially one that digs into personal or financial details—there's one rule you absolutely need to know : you can't use court-obtained documents for anything outside that case.
This isn't just good manners—it's a legal duty known as the Harman principle, or the implied undertaking rule.
It means that anything you receive through subpoenas, discovery, or other court processes stays strictly within the walls of that case—unless the court gives you permission to use it elsewhere.
This rule plays a huge role in family law and civil disputes, where things like bank records, medical reports, or personal affidavits are often involved.
It's there to protect people's privacy and make sure everyone feels safe enough to disclose what's needed.
At Unified Lawyers, we've helped clients navigate over 100 cases involving Harman obligations—and we understand just how important it is to get it right.
In this article, we'll walk you through what the Harman principle means, where it came from, how it applies in real-world family law matters, the rare situations where exceptions apply, and what can happen if you breach it.
What Is the Harman Principle?
The Harman principle (also called the implied undertaking or Harman undertaking) is a longstanding rule that documents and information obtained under a court's compulsory processes are to be used only for the purpose of that litigation.
In other words, if one party is compelled by the court (for example, by discovery obligations or a subpoena) to disclose certain documents, the other party undertakes not to use those documents outside the current proceeding.
This implied undertaking arises automatically as a matter of substantive law, not merely as a promise; it's an obligation owed to the court itself.
The principle got its name from the UK case Harman v Secretary of State for the Home Department (1983), and it has been firmly adopted into Australian law by cases like Hearne v Street (2008).
Origins and Historical Context
The Harman principle originated from a 1983 House of Lords decision in Harman v Home Department. In that case, a solicitor obtained confidential Home Office documents through discovery in a civil lawsuit and later gave those documents to a journalist.
The court found this to be a misuse of the documents and held her in contempt. The ruling established that a party who gains documents via court processes is under an "implied undertaking" to use them only for that case.
The Australian High Court emphatically endorsed this principle in Hearne v Street (2008), where Chief Justice French noted that this obligation is vital to encourage full and frank disclosure.
Key Components of the Principle
The Harman principle has several key components and practical consequences :
1. Who is bound :
It binds all parties to the proceeding, and extends to their lawyers and any third parties who legitimately receive the documents in connection with the case.
For example, experts, witnesses, or litigation support staff given access to discovered information are also bound by the same undertaking.
(Notably, it's not even required that these people know about the Harman obligation – as long as they know the documents came from a court process, they can be held liable if they misuse them.)
2. Scope of documents :
The obligation covers virtually all material obtained under compulsory court processes.
This includes documents produced on discovery or inspection, answers to interrogatories, subpoenaed materials, affidavits and witness statements filed under court directions, documents produced in compliance with court orders (like financial disclosures), and even information derived from those documents.
In short, if you got it through the court's power, it's covered.
3. Obligation to the court :
Importantly, the implied undertaking is regarded as an obligation to the court itself, not just to the opposing party.
This means that only the court can release or modify the obligation. Even if the party who produced the document consents to you using it elsewhere, you still need the court's leave to be formally released from the undertaking.
The duty typically survives even after the proceeding ends – it does not expire automatically when the case is closed.
Unless the material was aired in open court as evidence, the undertaking continues to bind the parties indefinitely or until a court says otherwise.
4. Exclusive purpose :
Any documents obtained can only be used for the purpose of the proceeding in which they were disclosed.
Using them for a collateral or ulterior purpose – for example, sharing them with the media, using them to start a new lawsuit, or leveraging them for a business advantage – would violate the undertaking.
Even using the information to pursue a different claim within the same case (beyond what was pleaded) can be a breach if it's fundamentally outside the original purpose.
5. Duration and end of obligation :
The obligation ends only in specific circumstances. One natural endpoint is if the document is tendered and received in evidence in open court – at that point, the material becomes part of the public record, and the undertaking ceases to apply to that information.
(Be careful: if only part of a document is read out or referred to in open court, the undertaking may lift only for that portion, not necessarily the whole document.)
Apart from that, the undertaking can be lifted by the court if you apply and convince the judge to grant you leave to use the material elsewhere (more on exceptions below).
Applications in Modern Ethics and Law
In today's legal practice, the Harman principle is a cornerstone of ethical litigation conduct.
It commonly arises in civil cases and is particularly significant in family law disputes involving sensitive information.
Harman Principle in Family Law
Family law litigants should be particularly aware of the Harman principle.
In family court proceedings – whether about property settlement or parenting arrangements – parties are required to make full and frank disclosure of financial and personal information.
This often includes bank statements, tax returns, valuations of assets, medical reports about parents or children, school records, and more.
The Family Law Rules in Australia explicitly reinforce the Harman obligation : Rule 6.04 of the Federal Circuit and Family Court of Australia (Family Law) Rules 2021 provides that a person who obtains a document by virtue of a family law proceeding "cannot use the document for any other purpose" and must not disclose it to any other person (subject to some limited exceptions).
In simple terms, if you receive your ex-partner's financial documents or affidavit through the Family Court process, you are undertaking to the court that you won't use them outside that court case.
This has very practical implications.
For example, suppose during a property settlement case you obtain your ex-spouse's bank statements and discover evidence of undisclosed income.
You might be tempted to share this with the Child Support Agency (CSA) to get a better child support assessment, or even to tell a mutual friend about your ex's finances.
Doing so would likely breach both Rule 6.04 and the Harman principle, because you'd be using the documents for a new purpose (outside the original property case).
In fact, under section 121 of the Family Law Act 1975 it's also an offence to publish or disseminate information from family law proceedings to the public, so family law has extra layers of confidentiality.
The Harman principle works in tandem with these laws – even a private sharing of documents (not necessarily "to the public") can violate the implied undertaking if it's not for the case.
Everyone involved in a family case is bound. This includes the parties' lawyers and barristers, and also any Independent Children's Lawyer (ICL) appointed to represent the child's interests.
An ICL often receives highly confidential reports (like psychological assessments of the child or parents) and they too cannot reveal or use that material outside the family court proceeding.
Courts sometimes make specific orders reminding parties of their Harman obligations in sensitive cases – for instance, when child welfare records or police files are subpoenaed into a parenting dispute, a judge may order that those documents "are not to be used except for the proceedings", echoing the Harman undertaking.
Although most commonly applied in civil and family cases, there have been discussions around the Harman principle and criminal proceedings—particularly where material from a criminal case may be sought in related civil litigation.
However, the principle's full force is generally reserved for civil contexts.
It's worth noting that even after a family law case concludes, the undertaking continues.
If you settled your matter or obtained final orders, you still must not take the documents from that case and use them elsewhere without court permission.
For example, a parent who obtained copies of the other parent's counselling records during Family Court discovery cannot later attach those records to a complaint against the counsellor or share them with a new partner – not without leave of the court.
The only partial exception in family law is if a document was admitted into evidence in open court, it enters the public domain to that extent.
But even then, Family Court secrecy provisions remain strict: one case noted that rule 6.04 and section 121 still applied to an affidavit even after it was read in court, since family law prioritizes privacy.
In short, family law practitioners and litigants must treat all court-obtained material as strictly confidential.
The court takes breaches very seriously, given the personal nature of the information.
The next section will discuss when you can get permission to use family law documents elsewhere – because there are a few narrow exceptions where the Harman obligation can be lifted.
Exceptions to the Harman Principle
While the Harman principle is strict, exceptions exist :
- Leave of the court : The main way to be released is to apply for leave.
- Consent of the producing party : Useful, but not sufficient on its own. Court approval is still required.
- Documents in the public domain : If documents were admitted in open court or are publicly available, the principle may not apply.
- Statutory exceptions : Sometimes overridden by specific laws (e.g., child support assessment).
- Independent acquisition : If you obtain the same document from another lawful, independent source, you may not be bound.
Risks & Consequences of Breaching the Principle
Consequences include :
- Contempt of Court : Misusing documents may lead to contempt charges.
- Adverse Cost Orders : You may be ordered to pay the other party's legal costs.
- Striking Out or Injunctions : The court can strike out parts of your case or issue an injunction.
- Professional Disciplinary Action : Lawyers can face misconduct charges.
- Reputation Damage : Future credibility and trust with the court may suffer.
- Real-world example : A solicitor in NSW was reprimanded and fined for annexing subpoenaed documents to an affidavit in another case without permission.
Frequently Asked Questions
1. What is the Harman legal principle in Australia?
It's a rule that prevents parties from misusing documents or information obtained under compulsion in court proceedings.
Known as the Harman legal principle, this obligation ensures disclosed documents—like affidavits or financial records—are only used for the case at hand, unless the court grants permission.
Depending on context, the Harman undertaking has also been discussed alongside broader legal ideas such as the compensation principle in Harman-type cases, though it remains a distinct confidentiality rule.
2. Is the Harman principle the same as legal professional privilege?
No. Privilege protects private conversations between a lawyer and their client.
The Harman principle is about how you can use documents once they've been shared in a court case.
Privileged documents might never be handed over; Harman applies to documents that have been disclosed.
3. Can I share court documents with family or the media?
Usually not.
Unless the court says it's okay, sharing with media or even close family can breach the Harman principle.
The only safe zone is your legal team or expert advisors involved in your case. If in doubt, check with your lawyer first.
4. What if the other party breaks the rule?
Tell your lawyer straight away.
The court can stop further use, order documents to be returned or destroyed, and even punish the person responsible.
If a lawyer was involved, they could face disciplinary action.
Act quickly — once something is shared, you can't undo it.
5. Are there exceptions in emergencies, like if the documents reveal a crime?
Yes, in urgent cases like risk of harm or serious crime, the court may excuse a breach.
Ideally, you should apply to the court first. If you must act fast (e.g. to protect someone), explain it to the court as soon as possible afterward.
6. How do I get permission to use documents in another case?
You'll need to ask the court for permission (called "leave"). Explain what documents you want to use and why.
The court will weigh things like fairness, privacy, and how related the cases are.
Don't use the documents until you have official approval.
Practical Guidance for Litigants
Checklist :
- Treat all disclosed documents as confidential.
- Seek legal advice before using documents elsewhere.
- Do not assume consent lifts the obligation.
- Apply to court if in doubt.
- Download our PDF summary for more tips.
How Unified Lawyers can help
Legal issues involving the Harman principle often intersect with complex litigation, sensitive family law matters, and strict confidentiality rules.
Whether you need guidance on using disclosed documents properly, applying for court permission, or responding to a breach, our experienced litigation and family law team can help you navigate your obligations confidently and lawfully.
At Unified Lawyers, we combine decades of experience in family and civil litigation with a strong ethical foundation.
Based in Sydney, our firm is a trusted advisor in cases involving subpoenas, document disclosure, and the Harman principle. As proud members of the Law Society, we act with professionalism and integrity in every case.
If you're unsure about how to handle confidential court documents or want to avoid breaching the Harman undertaking, get in touch today.
We'll provide practical legal advice tailored to your situation and help protect your position in court.
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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.
