[Book Review] Patent Claims: Interpretation, validity and infringement

This is a review of the book Patent Claims: Interpretation, validity and infringement (Federation Press, 2025) by David Brennan, a Visiting Fellow at the University of Technology, Sydney (UTS) Law Faculty.

This is a rare textbook that is worth reading from start to finish. It is difficult to tell a richly literary story in a patent context so deftly, but Brennan's work (and use of pertinent quotes to begin each chapter) inspired me to adapt some Shakespearean quotes to a patent context throughout this review.

Claims take centre stage

All the patent system's a stage, and all the claims merely players.

One of the first things that struck me was the starting point for this book. Rather than the typical preamble about the nature of patents or the policy justifications for exclusivity, Brennan unapologetically cuts straight to the heart of patents – the claims themselves. By starting with the claims, the book acknowledges that claims are not the endpoint of the drafting process, but the starting point from which construction, validity and infringement follow as downstream consequences of how specifications are drafted and read by the skilled reader.

Another striking feature of this book is that it is more than a mere reference text; it is also an exercise in historical storytelling. Brennan does not simply summarise the law as it stands, but explains how it arrived at its present form through a focused and informative historical narrative. Doctrines are traced through their development, with particular attention to how and why the claim came to prominence in patent law (which I was surprised to learn was not always the case). While setting out the historical perspective may slow the pace for those wishing to readily understand the current state of affairs, it both rewards the intellectually curious reader and is structured in a way that those looking for the "so what" can readily find it.

Part 1 – Introduction to patent claims

We are such stuff as dreams are made on, and our little life is rounded in 20 years.

Part 1 begins with a deceptively simple premise: "Claims are the fulcrum of modern patent law", and immediately launches into the history of how this came about. From the 1794 UK requirement for a written specification that did not require claims, Brennan explores the evolution of UK patent law to require specifications to include claims defining the monopoly, before turning to the Australian context. Aspects of the evolving patent landscape in Australia are discussed with reference to the move from a "first to invent" to a "first to file" system, the role of priority dates, and the origins of product claims to substances.

The discussion of product claims is a particularly interesting addition that is rarely discussed, providing a detailed history of how these claims – a stalwart of modern patent law that most modern-day patent practitioners likely take for granted – came to be.

Part 2 - Interpretation

What's in a claim? A claim by any other name would define the invention.

Claim interpretation is both an art and a science, and Brennan's analysis draws this out beautifully. Much of Part 2 is directed to exploring the evolution of purposive construction in Australia, while also highlighting how the courts have sought to embrace this doctrine arising from the UK courts. However, purposive construction has not received the same status in Australia as it has in the UK, leading to ambiguities that are certainly coming to the fore in recent case law (but that is a post for another day!).

Book Review Kat

Part 2 then moves on to a more detailed look at claim construction in Australia, highlighting the hybrid nature of Australia's patent system and the key role of the Federal Court in shaping the law in relation to claim construction. Brennan draws out some of the more interesting and controversial positions adopted by the Federal Court, including the strained construction of enantiomer claims adopted by the Full Federal Court. Bringing this analysis back to the unique Australian approach to purposive construction, Brennan illuminates how Australian law has diverged from the UK law in which it is rooted.

This section also touches on the role of prosecution history and amendments in claim construction, and different claim types – including omnibus claims, Swiss-style claims and Jepson claims – and their role in Australian patent law.

Part 3 - Validity

To claim, or not to claim, that is the question.

Part 3 is directed to validity, and perhaps the most interesting aspects of this section relate to some of the unique aspects of Australian patent law, including manner of manufacture (patentable subject matter), utility and best method. That said, the entire section is also an interesting and worthwhile read.

The concept of manner of manufacture dates back to the Statute of Monopolies 1623, and Brennan explores how the Courts have struggled to apply this concept to modern technologies, such as genetic material, diagnostic methods and computer-implemented inventions. The discussion of the substantialist approach to claim construction when assessing manner of manufacture is contrasted with the textualist approach explored in Part 2, and ends with a question for readers as to whether this dual approach represents good law.

Brennan also draws out Australia's unique approach to utility and best method. The three facets of utility under Australian law are explained, including the "promise" aspect – which requires the claimed invention to meet all of the promises set out in the specification, and can present particular issues for unsuspecting applicants in Australia. In relation to best method, Brennan also highlights the problems this ground of invalidity causes applicants in Australia, and posits that the adoption of the Biogen sufficiency concept into Australian law supports a case for repeal of the best method requirement.

Part 4 – Infringement

Some claims are great, some achieve greatness, and some have greatness thrust upon them.

Part 4 is directed to concepts of infringement, and explores key issues including patent exhaustion, prior use and indirect infringement. Chapter 15 presents a particularly interesting read, as it explores secondary liability in the context of authorisation, joint tortfeasorship and infringement by supply (indirect infringement). The discussion of authorisation – which continues to evolve before the Australian courts – is informative in relation to the role of company directors and parent companies in secondary infringement.

The verdict

Words are easy, like the wind; but good textbooks are hard to find.

Unlike most textbooks, this book tells a cohesive story that can (and, in my view, should) be read start to finish. For practitioners, the historical aspects are perhaps where the book becomes most interesting – it is one thing to know the current state of the law, but quite another to understand its foundations.

In addition to providing a rich historical context, Brennan also does not shy away from expressing his opinions and questioning the law. Where doctrines appear strained, or historically contingent, this is acknowledged directly. The reader is left with the sense that patent law is not a closed system, but one that remains open to reconsideration at the level of principle.

For those looking for commentary on current case law, you will not find a comprehensive overview here (and, in my view, this is necessarily not the realm of textbooks of this nature). But for those looking to deepen their understanding of patent law in Australia at the level of principle, this book is definitely for you.

All in all, this book is a welcome addition to Australia's relatively sparse landscape of patent law texts, providing readers with a deep understanding of the origins of the law, how it has evolved, and how it is applied today, all brought into focus through the unifying lens of the humble but undeniably significant patent claim.