Implied waiver of legal professional privilege — a cautionary tale

A recent decision offers a sharp reminder: if you deploy your solicitor's evidence to explain away delay, you may open the door to implied waiver of legal professional privilege (AstraZeneca AB v Pharmacor Pty Ltd (No 2) [2026] FCA 414).

How the solicitor's legal advice came into contention

AstraZeneca (AZ) sued Pharmacor for patent infringement. In its Defence, Pharmacor admitted the Patent would expire at the end of its extended term on 22 October 2027. Two months later, it then applied to amend its pleadings to challenge the validity of that very extension of term, and to withdraw its earlier admission.

Pharmacor had the opportunity to raise this challenge in its original pleadings, but chose not to do so. To explain the delay (a relevant factor on any amendment application) Pharmacor relied on its solicitor's affidavit evidence, which stated that "it was not until after the hearing on 6 February 2026 that the Respondent/Cross-Claimant (including its legal representatives) appreciated the merits" of the challenge.

AZ served a Notice to Produce seeking all documents recording consideration of the validity of the patent term extension before 20 February 2026. Pharmacor applied to set aside the Notice.

Pharmacor's three arguments – all rejected

Pharmacor advanced three arguments for setting aside the Notice:

1. The Notice was too broad. Pharmacor argued it was in the nature of a discovery category and not appropriately targeted. Justice Downes rejected this, finding that the expression "appreciated the merits" was vague and did not constitute the kind of candid explanation the Court expects when a party seeks an indulgence. Pharmacor had previously decided not to challenge the extension; the fact that it now wished to do so on one particular basis did not mean the Notice should be similarly confined.

2. The date range was wrong, because the Notice should only cover the period before 6 February 2026. This argument was also rejected. The evidence was that the merits were not appreciated until after 6 February 2026, but did not specify when. AZ had reasonably selected 20 February 2026: the earliest date on which Pharmacor's lawyers took steps relating to the patent extension.

3. The Notice would require production of privileged material. Justice Downes held that the usual course is for a party to produce documents and then claim privilege over specific items. The mere potential for privileged documents to be captured did not justify setting aside the Notice altogether.

The key finding: implied waiver of legal professional privilege

This is the critical takeaway. By relying on solicitor evidence that put in issue when and whether Pharmacor and its legal representatives considered the validity of the patent extension, both before and after 6 February 2026, Pharmacor had impliedly waived legal professional privilege over documents recording, evidencing, or relating to communications about those matters.

Justice Downes reasoned that maintaining the privilege would be inconsistent with the case Pharmacor itself wished to advance on both the amendment application and the withdrawal of its admission. In short, Pharmacor could not use its solicitor's evidence as both a sword and a shield.

The Court ordered production of documents within the scope of the Notice that were either not subject to a privilege claim, or over which privilege had been waived. AZ was given the opportunity to file further submissions and evidence after reviewing those documents, with Pharmacor to reply, and costs of the set-aside application were awarded to AZ.