This case related to the way in which the Australian courts construe qualitative terms in patent claims. In this case, the contentious term was not considered to be a term of art, so while extensive expert evidence was considered, it was the role of the Court to construe this term. Therefore, expert evidence was only relevant so as to assist the Judge in coming to a conclusion regarding the meaning of the contentious term within the context of the specification and claims.

The patentee, in having resorted to the qualitative claim term to distinguish the claims from the prior art, was assisted both at first instance and on appeal because it had described prior art in the specification. The patentee was also assisted by its characterisation of the qualitative term as providing an improvement. Under this approach to claim construction, patent drafters using qualitative terms in claims should consider describing prior art in the specification and consider incorporating comparative language in the claims in relation to the qualitative terms. Patent drafters and those prosecuting patent applications will of course need to be careful in making comparisons, so as to avoid making a false suggestion or misrepresentation about the claimed invention.1

Although ultimately successful, the patentee was not assisted by the use in the specification of the same qualitative claim term when describing the prior art. The case also reminds drafters that they should carefully consider the context in which they use terms that appear in the claims.


Ciba is the owner of five innovation patents relating to treatment of tailings from mineral processing operations. The technology broadly related to dewatering and compaction of tailings from a mineral processing operation by the addition of a polymer which caused particulate tailings to form floccs, resulting in improved compaction and dewatering.

Although there were five patents, it was agreed by both parties that the differences between the claims of each the innovation patents was immaterial to the case and that patent 2006100944 would serve as an exemplar.2

SNF brought proceedings against Ciba seeking revocation of the patents and relief from unjustified threats. Ciba brought a cross-claim for infringement of certain patents by SNF. Central to this decision was the construction of the term “rigidification” as recited in claim 1 (claim 1 is for a “process of improving rigidification”).

Ultimately, the trial judge (Kenny J) ruled in favour of Ciba, that the claims of the patent were valid and that SNF had infringed the claims. SNF appealed the decision on the basis that Kenny J had inappropriately construed the term “rigidification”.

How the term was construed by the trial judge

Kenny J determined based on the evidence provided that the term “rigidification” was not a term of art and her first recourse was to a dictionary definition of ‘rigidify’.3 Kenny J postulated that the question to be asked is “what does the word ‘rigidification’ signify in the specification and claims”.4 Furthermore, while “rigidification” may have a standard meaning, the patent was directed to a process of “improving rigidification” which must provide something more than the normal process of “rigidification” that is expected in natural settling and sedimentation processes.5

Kenny J considered the competing evidence provided by expert witnesses from each side noting that the evidence provided by the experts was “as to the scientific and industrial context in which the claimed processes would operate and in which ‘rigidification’ was to be understood”.6

There were two primary experts, Dr Farrow (for Ciba) and Prof. Slatter (for SNF). Both experts said that rigidification involved an increase in yield strength. Dr Farrow said that the rigidification process of the patent produced different characteristics, had different dewatering potential and acted on a different timescale to natural settling and sedimentation and that this resulted due to networking of the entire solid mass rather than entanglement of individual aggregates.7 Prof Slatter said that rigidification occurred as the last part of natural settling and sedimentation.8 Kenny J favoured the interpretation provided by Dr Farrow, commenting that that meaning provided by Dr Farrow accorded with the natural meaning of the word, considered in the context of the specification as a whole.9 Kenny J further commented that Prof Slatter’s interpretation of “rigidification” was “without having regard to what was evidently being taught [in the patent]”.10 Relevantly, Kenny J also took into consideration statements made by other relevant people working in the field, wherein these people had no difficulty in distinguishing between the process leading to improved rigidification in accordance with the process of the patent, and the standard process of sedimentation.11

Kenny J ruled in favour of Ciba.

The appeal

SNF appealed the decision on the basis that while it was for the Court to construe the claims, Kenny J had inappropriately construed the term “rigidification” by importing the definition proposed by Dr Farrow. Specifically, SNF contended that Dr Farrow’s evidence was not in keeping with that of the skilled addressee and that it was at odds with the language of the claims and the specification of the patent.12

One of the main areas of contention was that Dr Farrow had provided (and Kenny J had accepted) a definition for the term “rigidification” that included the formation of a network structure between floccs, and that this network structure resulted in a compacted sludge having a different structure to other processes. This feature of the compacted sludge having a networked flocc structure was not disclosed in any of the patents and it was not shown that this feature would have been apparent to the skilled addressee of the specification. Therefore, while SNF generally agreed in principle with the approach taken by Kenny J, they argued that there was no proper basis in the patent specification to import the “networking” feature into the term “rigidification” in the manner proposed by Dr Farrow (and adopted by Kenny J).13

All judges agreed that the networking of the solid mass was irrelevant to the construction of the claims.14 The majority Judges stated that Kenny J had adopted the correct approach, in that the question to ask was what the word “rigidification” signified in the specification and claims of the patent.15 In this regard, the majority Judges said it was important to take into account that the context was a process of improving rigidification and referred to the discussion in the patent specification of the prior art.16 On this basis, natural rigidification by settling and sedimentation were excluded from the claims.17 In regards to SNF’s argument against the improper importation of the “networking” feature into the term “rigidification”, the majority Judges stated that:

Dr Farrow’s explanation of a networked structure formed the basis of Ciba’s approach to the effect of improved rigidification, in part to explain its meaning, in that he explained the way in which the process worked. However, there is no requirement for the patentee to provide an explanation of how the invention works… The construction of the claim in the context of the specification does not depend on, or take account of, the concept of a networked structure or the evidence in relation to it”.18

Dowsett J wrote a strong dissenting judgement. He had difficulty identifying from the specification the distinction between rigidification on the one hand and settling and sedimentation on the other.19 As to the qualitative improvements referred to by Dr Farrow, Dowsett J found that these appeared only in dependent claims, not in the claim in dispute. He further found that Dr Farrow’s evidence was irrelevant, because it was based on the alleged infringing process and was providing a view of the knowledge and understanding of the skilled addressee.20

The approach of Dowsett J to construction therefore did not involve reliance upon the evidence of the experts. Instead, he referred to the ordinary meaning of rigidify and to the way in which the term was used in the specification, including in relation to the processes of settling and sedimentation.21 He described the approach adopted by the primary judge of defining the qualitative words “improving rigidification” as requiring a comparison with other processes as unsatisfactory. In particular, he said ‘there is a risk of circuitousness in using a known word to describe a new process, and then seeking to redefine the word by reference to that process.’22

SNF’s appeal was dismissed.