Background
Kumiai alleged that Kenso Corporation and Kenso Agcare infringed claims 1 and 5 of its innovation patent for a process to produce the herbicide pyroxasulfone, through dealings in Kenso’s KUDOS 850 WG Herbicide. Kenso denied infringement and cross-claimed for revocation on invalidity grounds.
Kenso sought leave to add a “best method” invalidity ground under s 40(2)(aa) of the Patents Act 1990 (Cth). It alleged that, although the specification presented the process as industrially advantageous, it disclosed laboratory examples rather than the industrial-scale process Kumiai was said to know. Kenso also sought to plead prior user. Kumiai sought responsive amendments alleging joint tortfeasorship and misleading or deceptive conduct based on Kenso’s failure to warn customers of alleged patent infringement.
The Court’s Holding
Rofe J granted Kenso leave to amend its cross-claim to add the best-method ground. The Court did not decide that the patent was invalid. It held only that the proposed ground was sufficiently arguable to proceed to trial, supported by the specification’s industrial-scale statements, expert evidence about scale-up requirements, and evidence capable of supporting an inference that Kumiai had relevant industrial manufacturing knowledge at the filing date.
The Court also allowed Kenso to plead its prior-user defence. It allowed Kumiai’s joint-tortfeasor amendment, but refused leave for its Australian Consumer Law claim in its proposed form. Because the alleged representation arose from silence—a failure to warn—the pleading needed material facts identifying the circumstances in which that silence conveyed the claimed representation. Kumiai was given leave to file a revised, properly particularised version. Discovery issues were referred to a Registrar.
Key Takeaways
- A best-method challenge may be pleaded without identifying the alleged undisclosed method precisely where the patentee’s knowledge is properly an issue for investigation.
- Whether a patent invention includes industrial-scale advantages may depend on the specification as a whole and is ordinarily a trial issue.
- An Australian Consumer Law claim based on silence must plead the circumstances making the silence allegedly misleading.
Why It Matters
The decision illustrates the relatively limited inquiry on an interlocutory amendment application in patent litigation: a party need show that its proposed invalidity ground is arguable, not that it will ultimately succeed. It also confirms that alleged overlap with existing technical and infringement issues can reduce the prejudice of a late amendment where trial is not imminent.
For patent owners, industrial-scale advantages stated in a specification may become relevant to a best-method challenge if the specification provides only laboratory-scale detail and there is evidence of commercial manufacturing knowledge at the filing date.