Neilson v Minister of Public Works (NSW)

The appeal concerned an application by Matthew Montgomerie Neilson to amend a patent specification for an invention described as the "Non-septic treatment of sewage and other organic liquid." The Commissioner of Patents had refused certain proposed amendments, and Neilson appealed this decision to the High Court of Australia. The core of the dispute revolved around whether the proposed amendments sought to claim an invention substantially different from that originally described, and whether the amended claims disclosed patentable subject matter.

The High Court was required to determine two primary legal issues. Firstly, whether the proposed amendments to the patent specification offended section 78 of the *Patents Act 1903*, which prohibits amendments that would make the specification claim an invention substantially larger than or substantially different from the invention originally claimed. Secondly, the Court had to consider whether the claims set out in the proposed amendments disclosed patentable subject matter, particularly in light of the existing technology for sewage treatment.

The Court's reasoning varied amongst the judges. Griffith C.J. found the amendments to be properly disallowed on both grounds: that the proposed invention was substantially different from the original claim, and that it lacked patentable subject matter. Barton J. agreed that the amendments were prohibited by section 78. Isaacs, Gavan Duffy, and Rich JJ. focused on the lack of patentable subject matter, reasoning that the proposed claims amounted to a mere working direction or a suggestion to use existing apparatus in a particular way to achieve better results, rather than a new invention or process with practical means for its implementation. They concluded that the claims did not add to the sum of human art in a patentable sense.

The appeal was dismissed, with the High Court upholding the Commissioner's refusal to allow the proposed amendments to the patent specification.