Privilege 

Most of the rules covered elsewhere in this module exclude evidence because of a concern about its reliability or its fairness to the fact-finding process. Privilege is different. It excludes relevant, reliable evidence for a reason entirely outside the trial process: the protection of a relationship or interest that society values enough to accept the cost of losing that evidence.

Client legal privilege

The central evidentiary privilege is client legal privilege (also called legal professional privilege). It protects confidential communications made between a lawyer and their client, and confidential documents prepared, for the dominant purpose of the lawyer providing legal advice to the client, or for the dominant purpose of actual or contemplated litigation. Both limbs share the same underlying structure: confidentiality, and a dominant purpose connected to legal advice or to litigation.

The dominant purpose test, confirmed in Esso Australia Resources Ltd v Commissioner of Taxation (1999) 201 CLR 49,¹ is the key to applying the privilege correctly. A communication made for several purposes is only privileged if the legal advice or litigation purpose was the ruling, most influential purpose behind it, not merely one purpose among several of comparable weight. A document created for a mix of commercial and legal reasons, where the commercial reason predominates, will not attract the privilege merely because a lawyer was copied in or briefly consulted. Confidentiality must also be maintained — a communication that has been disclosed to third parties outside the privileged relationship, or made public, will generally lose the protection.

Privilege belongs to the client, not the lawyer, and can be waived by the client, expressly or by conduct inconsistent with maintaining confidentiality — for example, by voluntarily disclosing the substance of privileged advice to a third party or deploying it in the proceeding.

Why the privilege exists

The rationale is functional rather than evidentiary: client legal privilege exists to encourage full and frank disclosure between a client and their lawyer. A client who feared that anything said to their lawyer could later be produced in court would be discouraged from being candid, undermining the lawyer's ability to give properly informed advice and to represent the client effectively. The law accepts the cost of excluding evidence that may be genuinely relevant and reliable because the systemic benefit — clients who can speak openly to their lawyers, and lawyers who can therefore advise and act competently — is judged to outweigh the loss of that evidence in the individual case. This is why privilege can be asserted even over evidence that is highly relevant and completely trustworthy: unlike hearsay or opinion evidence, its exclusion has nothing to do with doubts about the evidence itself.

Other recognised privileges

Client legal privilege is the privilege most heavily tested and most frequently litigated, but it is not the only one. The privilege against self-incrimination allows a person to refuse to answer a question, or produce a document, where doing so would tend to expose them to a real risk of prosecution or penalty, reflecting a broader principle that a person should not be compelled by legal process to become the instrument of their own conviction. Statutory regimes in some contexts modify or abrogate this privilege, so its availability cannot be assumed without checking the specific proceeding.

Without-prejudice privilege (also called settlement privilege) protects communications genuinely made in a bona fide attempt to negotiate the settlement of a dispute from later being used as evidence of admissions in subsequent litigation over that dispute. Its rationale mirrors client legal privilege's functional logic: parties are more likely to negotiate candidly, and disputes are more likely to settle efficiently, if settlement discussions cannot later be weaponised as concessions if negotiations fail.

Applying this in a problem question

1. Identify the communication or document said to be privileged, and who created it and for whom.
2. For client legal privilege, ask whether it was confidential and made for the dominant purpose of legal advice or of actual or contemplated litigation.
3. Check whether confidentiality has been lost, or the privilege waived, through disclosure to a third party or inconsistent conduct by the client.
4. If client legal privilege does not fit the facts, consider whether self-incrimination privilege or without-prejudice privilege is more clearly engaged instead.
5. Remember privilege operates independently of relevance and reliability — do not argue against it merely by pointing to how probative the evidence would be.