Australia: Specification Key To Unlocking Prior Art Admissions

Last Updated: 20 September 2006
Article by Andrew Lowe and Russell Davies


The Full Court of the Federal Court has dismissed an appeal by Lockwood Security Products Pty Ltd (Lockwood) and has held that several claims in Lockwood’s Australian Patent No. 702534 (the Patent) were invalid for being obvious. In addition, the Full Court also held that Doric Products Pty Ltd (Doric) did not infringe those claims that covered the preferred embodiment of the invention described in the Patent. This case reminds practitioners and patentees of the need to carefully draft patent specifications when describing known prior art.

Background to the Judgement

In Lockwood Security Products Pty Ltd v Doric Products Pty Ltd (2004) 214 CLR 274, the High Court of Australia held that the claims of the Patent were fairly based and remitted the matter back to the Full Court to determine the remaining issues of infringement of the claims defining the preferred embodiment of the invention described in the Patent (the preferred embodiment claims) and obviousness of the broader claims of the Patent.

The Patent related to a "deadlock", which has an inner lock and an outer lock, allowing the deadlock to be locked from the outside or the inside of the door. The Patent broadly claimed a deadlock in which the inner lock could be unlocked from the outside when the key unlocks the outer lock. The invention was designed to prevent a person being accidentally locked inside when the key is lost or left within the outer lock.

The Full Court Judgement

The Full Court upheld the trial judge’s finding that Doric did not infringe the preferred embodiment claims of the Patent on the basis of the evidence presented at trial.

In respect of the validity of the broader claims, the Full Court held that these claims were invalid on the ground of obviousness. The specification of the Patent described the problem of the prior art as being that the inner lock could not be unlocked from the outside, and the object of the invention was to make the inner lock release at the same time as the outer lock by actuation of the key. The expert evidence called by both Doric and Lockwood showed that the "solution" described as the object of the invention was well known. What was not known was how to implement this solution; that is, the exact mechanics to make the solution work.

The Full Court concluded that the problem was admitted in the specification as being part of the common general knowledge in the technical field. On this basis and the expert evidence, the Full Court held that the broader claims were obvious because they claimed the concept of any means of releasing the inner lock from the outside of the door, and not how the inner lock was released, unlike the preferred embodiment claims.

Doric also submitted that the broader claims were invalid on the ground of insufficiency under subsection 40(2)(a), which requires that the specification must describe the invention fully, including the best method known to the applicant of performing the invention. Doric argued that the invention had not been described fully because the consistory clause (mirroring claim 1 of the broader claims) misleads the reader as to the improvement, being the preferred embodiment. In addition, the broader claims of the Patent were not warranted by the disclosure in the specification of the preferred embodiment. In making these submissions, Doric relied on the earlier High Court decision of Sami S Svendsen Inc. v Independent Products Canada Ltd (1968) 119 CLR 156, decided under the previous Patents Act 1952. In that case, it was held that a patent for a sausage holder was invalid for failing to describe the invention because the specification "did not enable the reader to discern what was the invention in the total thing that it describes".

The Full Court rejected Doric’s submissions because they mixed sufficiency with fair basis. The element of Sami Svendsen relied on by Doric was not good law because the word "invention" in Sami Svendsen was used in relation to inventive step, whereas the High Court said that "invention" in s40 did not mean "inventive step", but included an alleged invention and "the embodiment which is described, and around which the claims are drawn".

The Full Court held that subsection 40(2)(a) only requires a patentee to describe the invention so that a skilled addressee would understand what the invention is and how it is best worked. It was not necessary for the patentee to identify the inventive step involved in the invention, as this should be properly dealt with on the separate ground of obviousness. Thus, the patent complied with sufficiency requirements under subsection 40(2)(a).

An application for special leave to appeal to the High Court from the Full Court decision was recently filed.


The decision in this case turned on the characterisation of the problem in the specification. As the problem and object of the invention were expressed in such a way as to suggest the solution that was the subject of the broader claims of the Patent, this led to the finding of obviousness of those broader claims. It is clear from this case that patent specifications should be carefully drafted to ensure that the claimed invention does not appear to be readily apparent from the manner in which the problem in the prior art is described. Otherwise, the broader claims of the patent are likely to be vulnerable to an attack on the ground of obviousness.

The case also clarifies what is necessary to meet the statutory requirement of sufficiency, and the Full Court has confirmed that patentees are not obliged to identify the inventive step in the patent specification.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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Andrew Lowe
Russell Davies
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