Canada: Common Sense And Obviousness: Supporting Evidence Is Required

Last Updated: June 15 2012
Article by Ken Bousfield

Whether enforcing a patent or prosecuting a patent application, obviousness is often the key issue. The Patent Examiner (in the case of a patent application) or the Court (in the case of an issued patent) must determine if a claimed invention is obvious in view of the prior art and the knowledge and skill or persons of ordinary skill in that art. In Mintz v. Dietz & Watson the United States Court of Appeals for the Federal Circuit (the Federal Circuit) held that bald conclusory statements that a claimed invention is obvious in view of "common general knowledge", are unacceptable unless supported by objective evidence.

An argument that a claimed invention is obvious is necessarily a fictional exercise based on hindsight. Obviousness is an issue neither of what was done, nor of what could have been done (all inventions could have been made before – but were not). Rather it is what that person skilled in the art would have done. In both Canada and the U.S., an obviousness analysis requires determination of:

  1. the level of skill and knowledge of a person of ordinary skill in the art.
  2. the scope and content of the prior art.
  3. the differences between the claimed invention and the prior art.
  4. whether the differences over the prior art are obvious.1

In the end, step (iv) is still a subjective determination of whether a person of ordinary skill, would, in the light of the state of the art and of common general knowledge, have come directly and without difficulty to the claimed invention2.

It is easy, once the teaching of a claimed invention is known, to say, "I could have done that." Before the assertion can be given any weight, one must have a satisfactory answer to the question, "Why didn't you?"3 In both the U.S. and Canada the courts guard against impermissible hindsight analyses by requiring that prior art be considered as if by a person not having knowledge of the claimed invention, without using the claimed invention as a road-map. An important part of that safeguard against impermissible hindsight analyses is the requirement that an Examiner or a judge provide a clearly articulated reason as to why it would be obvious to combine or modify the prior art to arrive at the claimed invention.

Applicants commonly face rejections that rely on conclusory assertions that "it would have been obvious to a person of ordinary skill in the art to ..." These assertions, generally symptomatic of impermissible hindsight analyses, are typically not supported by any evidence, and are often found in the context of a rejection made that the claimed feature missing from the art is "common general knowledge", or is a matter of "design choice." The lack of evidence is usually quite telling: if something is genuinely "common general knowledge" then there should be an abundance of sources for the Examiner to cite. The habit of relying upon unsupported conclusory statements has been harshly criticised by the Federal Circuit on previous occasions – see, for example, In Re Lee4 or In re Kahn5.

Mintz v. Dietz & Watson is a reaffirmation that bald conclusory statements cannot be the basis of a rejection for obviousness. The Mintz claims pertained to a sausage encasement that included an interlocking netting arrangement producing a checkerboard pattern on the surface of the meat. The trial judge relied on a "commons sense view" or "common sense approach" to hold that it was obvious to try a locking engagement.

On appeal, the Federal Circuit held mere recitation of the words "common sense", without any support to be a clear error6. The Court stated:

Common sense is a shorthand label for knowledge so basic that it certainly lies within the skill set of an ordinary artisan. With little more than an invocation of the words common sense (without any record support showing that this knowledge would reside in the ordinarily skilled artisan), the district court over-reached in its determination of obviousness7.

The Court concluded that the trail judge erred by failing properly to consider the objective evidence of the patentee, and instead basing the decision on an unsupported conclusory statement.

In requiring that alleged "common sense" must be supported by an objective basis in evidence, the Mintz decision is a welcome relief.


1 Graham v. John Deere Co. 383 US 1 (1966), sometimes referred to as the "Graham factors".

2 Beloit Canada v. Valmet Oy, (1986) 8 CPR (3d) 289 (FCA per Hugesson) at 294.

3 Beloit Canada v. Valmet Oy, supra, at 295.

4 In re Lee, 277 F.3d 1338 (Fed. Cir. 2002),

5 In re Kahn, 441 F.3d 977 (Fed. Cir. 2006)

6 Mintz, page 8, lines 26 - 29

7 Mintz page 8, line 29 – page 9, line 4.

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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Ken Bousfield
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