In the recent decision of Wake Forest University Health Sciences v. Smith & Nephew Pty Ltd. (No.2) [2011] FCA 1002 a patent was ruled invalid because the meaning of an essential integer of the claims could not be determined. The decision highlights the importance of understanding the science behind how an invention works and ensuring that the claim language reflects the science.  

Background and relevant facts

Wake Forest University Health Sciences and KCI Medical Australia Pty Ltd (collectively "KCI") alleged that Smith & Nephew Pty Ltd. ("S&N ") had infringed 14 claims of Australian Patent No. 674837 by the sale of wound healing kits including a foam dressing and vacuum pump for applying negative pressure to a wound.

The cross-claim for revocation: was a key integer meaningless?

S&N cross-claimed for revocation of the patent, contending that the patent was invalid on a number of grounds including: lack of novelty, lack of inventive step, lack of clarity, lack of fair basis, lack of sufficiency and failure to define the invention. These claims were based largely on the assertion that an essential functional integer common to all of the claims in suit was meaningless and scientifically flawed. This so-called "screen rigidity integer" called for a "a screen means...sufficiently rigid to prevent wound overgrowth".

Conflicting expert evidence

Extensive expert evidence was led by both parties in relation to the function of this integer. It was common ground between the experts that, whilst not commonly used, the term "wound overgrowth" meant over-proliferation of granulation tissue to an extent that the tissue extends above the level of the skin surrounding the wound (which is known as hypergranulation). However, the experts opinions of the role the screen played in preventing over-proliferation of granulation were divergent:

  • KCI's experts understood that the rigidity of the screen means is such that it functions to modulate the growth of granulation tissue to an extent that over-proliferation is avoided.
  • S&N's experts stated that hypergranulation was a rare occurrence and opined that the screen means had no part to play in preventing hypergranulation. In this regard it was stated by S&N's experts, and ultimately conceded by one of KCI's experts, that hypergranulation is prevented by removal of the kit by a clinician. It was further noted by S&N's experts that if faced with the task of selecting a suitable dressing to prevent over-proliferation of granulation, they would not know what to select.

Ultimately, KCI submitted that the screen means modulates the growth of granulation tissue until a clinician makes a decision to intervene, and that the phrase "prevent overgrowth of granulation tissue" should be construed as a reference to the modulation of the growth of granulation tissue.

The decision

Justice Dodds-Streeton found that the claim construction advanced by KCI was inconsistent with the claim language, and that the screen means did not function in the manner described in the description of the patent. Noting that three of S&N's experts were unable to attribute a meaning to the screen rigidity integer, her Honour concluded that the meaning of the integer was unclear. In light of this fundamental deficiency S&N's cross-claim succeeded on the following grounds:

  1. Lack of clarity: whilst ambiguities in claims may often be resolved by reference to the specification, her Honour noted that the "obscurity and uncertainty" associated with the screen rigidity integer could not be rectified by reference to the specification because "the same deficiencies characterised the discussion of the integer" in the specification.
  2. Sufficiency: her Honour found that in light of the "meaningless nature" of the screen rigidity integer, and because S&N's experts would not have known what dressing to select, the specification did not provide sufficient guidance in relation to construction of a screen which would achieve the promised result, i.e., prevention of over-proliferation of granulation.
  3. Failure to define the invention: this finding was the result of the screen rigidity integer lacking inherent meaning.

Whilst claim 49 was found to be a "mere collocation" and hence invalid on the ground of lack of manner of manufacture (consistent with the previous findings of the Full Federal Court),1 the remaining grounds of invalidity relied on by S&N, including novelty and inventive step, were not made out. As such, with the exception of one claim, the patent fell entirely on the uncertainty surrounding the screen rigidity integer.

Lessons for patentees

It is crucial that the invention be described fully and accurately and that all integers of a claim do actually function in the manner described in the specification.

Care should also be exercised so as to avoid adopting claim language that is not based on sound scientific logic and reasoning, and which does not have a well understood meaning to persons skilled in the art.  

Failure to adhere to these principles will render a patent vulnerable to revocation on at least the ground of lack of clarity.