IP monitor: Ambiguity is unambiguously a live ground to invalidate patent claims

The Federal Court recently invalidated patent claims on the ground of ambiguity – an unusual holding. In Tekna Plasma Systems Inc. v AP&C Advanced Powders & Coatings Inc.¹, Justice McHaffie concluded that the claim term “depletion layer” lacked clarity and was ambiguous, making it impossible for a skilled person to understand the meaning of the term and know or determine whether or not the claimed subject matter (a metal powder particle) has a depletion layer within the scope of the patent claims. 

The court held that “[a] lack of clarity or potential competing constructions is not alone fatal. It is therefore a rare case where the Court will conclude that the claims of a patent cannot be meaningfully understood.” One patent was held to be invalid, a second patent was held to be invalid in part (a few claims were valid) and both patents were not infringed. 

This case signals that ambiguity is a live invalidity ground rooted in the statute, underscores the fundamental principle to provide fair and reasonably predictable public notice of the claimed patent monopoly, and highlights the importance of clearly defining claim terms, especially if they are “coined” (versus terms known or understood in the art), to avoid a self-inflicted wound.

Background

Tekna and AP&C produce reactive metal powders (e.g., titanium powders) that may be used in additive manufacturing, sometimes referred to as 3D printing. Two patents owned by AP&C were at issue: Canadian Patent Nos. 3,003,502 (502 Patent) and 3,051,236 (236 Patent). Tekna commenced impeachment and non-infringement actions for the 502 and 236 Patents. AP&C counterclaimed alleging infringement. 

The 502 Patent and 236 Patent are closely related stemming from divisional applications and share common inventors and an almost identical disclosure (except for different paragraph numbering). Both patents relate to processes for manufacturing metal powders through atomization, and differ regarding their claims, with each patent claiming particular processes and systems. The claims contain the term “depletion layer,” an essential element, the purposive construction of which was the crux of the dispute between the parties. Tekna’s main validity challenge was that the term “depletion layer” was ambiguous and not clearly defined rendering the patents unenforceable.

Claim construction of “depletion layer”

All parties and experts agreed that the term “depletion layer” is a term coined by the inventors that does not have a shared meaning to a skilled person based on the person’s knowledge of the art (field of powder manufacturing). Both parties turned to the disclosure of the 502 Patent and 236 Patent to ascertain the meaning of “depletion layer.” 

The main question identified by the court was whether a skilled person would be able to distinguish between a particle that has a depletion layer and one that does not.  

For the 502 Patent, the court concluded that a skilled person would not be able to answer this question. The court reached the same conclusion for the 236 Patent, with the exception of a few claims. Overall, the court held that “[n]either the claims nor the disclosure of the patents provide the reader with the ability to understand and assess whether a particle has a depletion layer, and thus whether a given process or system reads on the claims or not. In the words of Justice Binnie … the public reading the patents simply cannot know ‘where they can go with impunity’.”

Validity – 502 Patent

Justice McHaffie held that despite the court’s disinclination to invalidate claims for ambiguity, in this case, it was impossible for the skilled person to know in advance whether or not a process for producing a metal powder would fall within the 502 Patent claims, thus concluding the claims were ambiguous, and further held that:  

… despite the POSITA’s willingness to understand the claims and disclosure of the '502 Patent, they would be simply unable to assess whether a particular powder particle has a depletion layer that is deeper and thicker than the native oxide layer. The patent itself gives no indication of the parameters of such a layer, and the various proposals put forward by the experts and AP&C are either entirely inconsistent with the language of the claims or provide no predictable and meaningful manner of determining whether the essential element of the claim is met, or both. (bold emphasis added)

The court held that its findings regarding ambiguity are determinative of the validity of the 502 Patent – all claims are invalid. 

Validity – 236 Patent

The court concluded that various claims were invalid for ambiguity as they did not specify a manner of determining the existence of a depletion layer, which in turn did not allow the skilled person to know what falls inside the claims and what does not (identified as the “Ambiguous Claims”). However, there were a few claims that did provide the skilled person with a method of determining the parameters of the depletion layer, identified as the “Unambiguous Claims.”

The court did not address insufficiency allegations put forth by Tekna as they largely overlapped with ambiguity. However, the court briefly considered the grounds of inutility and overbreadth advanced by Tekna for the Unambiguous Claims. The court concluded that the Unambiguous Claims are useful despite the criticisms and shortcomings in the experiments and the descriptions in the patent and further concluded that Tekna did not show these claims are invalid for being overbroad.

Infringement – 502 and 236 Patents

The court held that the 502 Patent was not infringed, based on the legal principle that invalid claims cannot be infringed. The court similarly concluded that the Ambiguous Claims of the 236 Patent were not infringed. Regarding the Unambiguous Claims, AP&C did not assert that Tekna infringed these claims. 

For both patents, Justice McHaffie indicated that conducting an infringement analysis in the alternative was impossible in view of the ambiguity of the claims and instead in obiter considered the infringement and non-infringement evidence and theories put forth by AP&C and Tekna, respectively, regarding the meaning of “depletion layer”:

• AP&C’s Infringement Evidence: The court concluded that AP&C’s evidence does not demonstrate infringement of the 502 Patent. AP&C’s evidence relied on unestablished premises that introduced arbitrary and subjective parameters, and compared results from Tekna samples to AP&C commercial batch samples versus comparing to the results reported in the patent. The court similarly concluded that AP&C’s evidence does not demonstrate infringement of the 236 Patent and applied the 502 Patent analysis where applicable in reaching this conclusion.  
• Tekna’s Non-Infringement Evidence: The court held that Tekna’s evidence, while not clearly determinative (given that the term depletion layer is ambiguous), nonetheless provides a further basis to conclude that Tekna has not infringed the claims of the 502 Patent. The court reached a similar conclusion for the 236 Patent.  

Conclusion

The court concluded that the inventors did not distinctly and explicitly define the scope of their invention in a manner that allows the public or the court to determine its boundaries (except for the Unambiguous Claims). In doing so, the court rejected AP&C’s attempt to introduce a comparative testing approach to understand the claim boundaries as it did not stem from a reasonable purposive claim construction and also introduced arbitrariness and subjectivity. 

Failing to include sufficient information to allow a skilled person to know what does or does not fall within the scope of the claims, following a fair and purposive construction, is a self-inflicted wound that “cannot be corrected by imposing or reading in new standards or points of reference that are not found in the patent and cannot be reasonably understood from the claim language as drafted.”