Canada: Implicit Common General Knowledge Renders Claims Obvious: Tetra Tech EBA Inc. v. Georgetown Rail Equipment Company


The Federal Court of Appeal recently published its decision in Tetra Tech EBA Inc. v. Georgetown Rail Equipment Company, reversing the judgment of the court below to find the patent claims at issue invalid for obviousness.

The appeal concerned the validity and potential infringement of two patents, one for a railroad track inspection system and method (the "082 patent") and the other for a method for determining rail seat abrasion of a railroad track (the "249 patent").[1] Georgetown alleged that Tetra, a competitor in the field of machine vision systems for railroad track inspection, infringed the patents with its Three Dimensional Track Assessment System ("3-D TAS"). Tetra denied infringement, and counterclaimed for declarations that the claims of both patents were invalid on the basis that they were obvious.

The Federal Court of Appeal allowed Tetra's appeal, holding that the 082 patent claims were obvious. The Federal Court had failed to analyze how a skilled person would have applied the prior art using her common general knowledge.[2] The Federal Court of Appeal held that the Federal Court's findings about the common general knowledge implicitly contained everything necessary to bridge the gap between the state of the art and the inventive concept of the claims. Even though the Federal Court made no explicit findings on the point, the Federal Court of Appeal held the claims to be obvious.[3]

The Federal Court of Appeal also held that the Federal Court should have held the asserted 249 patent claims to be obvious.[4]

The Federal Court Decision

With respect to the 082 patent, at trial, the Federal Court held that none of the prior art identified plate cut – wear to railroad ties over time – as a rail defect to be detected by machine vision inspection systems or suggested solutions to detect it.[5] The Court further noted that the prior art did not describe any systems or methods comparable to those disclosed in the 082 and 249 patents.[6] On that basis, the Federal Court held that the patents required invention and were not obvious as of the priority dates.

Justice Fothergill found that Tetra's sale and use of 3-D TAS infringed both patents.[7]

The Appeal

With respect to the 082 patent, the Federal Court of Appeal concluded that the Federal Court erred in law by failing to consider how a person skilled in the subject matter would have applied the common general knowledge to the prior art.[8] Had the Federal Court done so, the lower Court would have concluded that the gap between the prior art and the 082 patent could have been bridged by a skilled worker applying only common general knowledge.[9]

The Federal Court of Appeal reviewed the Federal Court's earlier holding that the common general knowledge included that a machine vision system could be used to identify "rail defects".[10] The Federal Court of Appeal held that plate cut, the particular rail defect at issue, was implicit in the general description "rail defects". Thus, the skilled person would have known that plate cut could have been identified by machine vision inspection systems.[11] Had the Federal Court considered the common general knowledge, it would have held that the claims were obvious.

With respect to the 249 patent, Justice Dawson further concluded that the asserted claims were invalid for obviousness.[12] The only meaningful difference between the impugned claims and the prior art was a reference point chosen for measuring height differences between a railroad crosstie and the "tie plate" in order to calculate rail seat abrasion.[13] The Federal Court of Appeal concluded that there was nothing inventive in choosing a reference point for calculation, and held that the claims were obvious.[14]

The Federal Court of Appeal remitted the validity of the balance of the claims of the 249 patent to the Federal Court for reconsideration.[15] These claims contained an additional essential element, "tilt correction factor". Assessing whether these claims were also obvious was a largely factual issue that the Federal Court was best placed to determine.[16]


[1] Tetra Tech EBA Inc. v. Georgetown Rail Equipment Company, 2019 FCA 203 at para. 1 ("Tetra FCA").

[2] Tetra FCA at para. 63.

[3] Ibid at paras. 66, 71-73.

[4] Ibid at para. 134.

[5] Georgetown Rail Equipment Company v. Rail Radar Inc., 2018 FC 70, at para. 146 ("Tetra FC").

[6] Tetra FC at para. 148.

[7] Ibid at para. 187.

[8] Tetra at para. 63.

[9] Ibid at paras. 66, 71.

[10] Ibid at paras. 42-50.

[11] Ibid at paras. 65-66.

[12] Ibid at para. 14.

[13] Ibid at paras. 129-30.

[14] Ibid at para. 130.

[15] Ibid at para. 134.

[16] Ibid at para. 133.

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