Person Skilled in the Art

Patents are addressed to the person skilled in the art. In the case of patents of a highly technical and scientific nature, the person skilled in the art may be someone possessing a high degree of expert scientific knowledge and skill in the particular branch of science to which the patent relates.

In my view it is a well established principle that a patent specification is addressed, not to the public generally, but to persons skilled in the particular art.

…

[I]n the case of patents of a highly technical and scientific nature, that person may be someone possessing a high degree of expert scientific knowledge and skill in the particular branch of science to which the patent relates.

[p. 521; pp. 524-25]

In the context of an obviousness analysis, the notional skilled person has been referred to as a technician, who is skilled in the art but possesses no scintilla of inventiveness or imagination.

The classical touchstone for obviousness is the technician skilled in the art but having no scintilla of inventiveness or imagination; a paragon of deduction and dexterity, wholly devoid of intuition; a triumph of the left hemisphere over the right. The question to be asked is whether this mythical creature (the man in the Clapham omnibus of patent law) would, in the light of the state of the art and of common general knowledge as at the claimed date of invention, have come directly and without difficulty to the solution taught by the patent. It is a very difficult test to satisfy. [p. 294]

The person skilled in the art:

• is a hypothetical person;
• has a mind willing to understand a specification; and
• is someone who is going to try to achieve success and not one who is looking for difficulties or seeking failure.

44 … The patent is not addressed to an ordinary member of the public, but to a worker skilled in the art described by Dr. Fox as

a hypothetical person possessing the ordinary skill and knowledge of the particular art to which the invention relates, and a mind willing to understand a specification that is addressed to him. This hypothetical person has sometimes been equated with the reasonable man used as a standard in negligence cases. He is assumed to be a man who is going to try to achieve success and not one who is looking for difficulties or seeking failure.

(Fox, supra, at p. 184)

It is the common knowledge shared by competent ordinary workers that is brought to bear on the interpretation: Fox, supra, at p. 204; Terrell on the Law of Patents (15th ed. 2000), at p. 125; I. Goldsmith, Patents of Invention (1981), at p. 116.

The person skilled in the art is deemed to be sufficiently versed in the art to which the patent relates to enable them to appreciate the nature and description of the invention.

[53] … the patent specification is not addressed to grammarians, etymologists or to the public generally, but to skilled individuals sufficiently versed in the art to which the patent relates to enable them on a technical level to appreciate the nature and description of the invention: H. G. Fox, The Canadian Law and Practice Relating to Letters Patent for Inventions (4th ed. 1969), at p. 185. The court, writes Dr. Fox, at p. 203, must place itself

in the position of some person acquainted with the surrounding circumstances as to the state of the art and the manufacture at the time, and making itself acquainted with the technical meaning in that art or manufacture that any particular word or words may have.

See also D. Vaver, Intellectual Property Law (1997), at p. 140. Knowledge of purpose is one of the important attributes the skilled worker brings to the exercise, as was made clear in Burton Parsons Chemicals, Inc. v. Hewlett-Packard (Canada) Ltd., [1976] 1 S.C.R. 555, a case that concerned the validity of a chemical patent. The invention was a type of conductive cream to be smeared on bits of the human body for the purpose of making electro-cardiograms and the like. The mixture was of no fixed composition. The essential invention was to combine a highly ionizable salt with an aqueous emulsion (p. 564). It was put in evidence that hundreds, if not thousands, of substances would fit the description, including some that would be toxic or irritating to the skin. A toxic conductive cream would not be a useful therapeutic tool, and it was alleged on that account that the patent lacked utility and was invalid. These objections were swept away by Pigeon J. who held that the notional skilled workman would understand perfectly well the purpose of the combination and could therefore be expected to apply the teaching of the patent by sensibly choosing components suitable for that purpose (p. 563):

While the construction of a patent is for the Court, like that of any other legal document, it is however to be done on the basis that the addressee is a man skilled in the art and the knowledge such a man is expected to possess is to be taken into consideration. To such a man it must be obvious that a cream for use with skin contact electrodes is not to be made up with ingredients that are toxic or irritating, or are apt to stain or discolour the skin.

Burton Parsons is a pre-Catnic instance of purposive construction where, as in Catnic itself, the skilled addressee made sense and purpose of the words used in the claim by deploying the common knowledge of someone in that position. It is through the eyes of such a person, not an etymologist or academic grammarian, that the terms of the specification, including the claims, must be read.

An ordinary worker possesses common knowledge in the trade, not inside information or in-house knowledge.

[70] … Someone with Mr. Pielemeier’s connection to the respondents, burdened as he is with inside information, is not a very satisfactory proxy for the ordinary worker. He is a skilled addressee but he is not operating on the basis of common knowledge in the trade. The patent claims were not addressed by Whirlpool’s research engineers to their colleagues in Whirlpool’s product development group. The patent claims were necessarily addressed to the wider world of individuals with ordinary skills in the technology of clothes washing machines. As Aldous L.J. observed in Beloit Technologies Inc. v. Valmet Paper Machinery Inc., [1997] R.P.C. 489 (Eng. C.A.), at p. 494:

The notional skilled addressee is the ordinary man who may not have the advantages that some employees of large companies may have. The information in a patent specification is addressed to such a man and must contain sufficient details for him to understand and apply the invention. It will only lack an inventive step if it is obvious to such a man. [Emphasis added.]

Dickson J. placed the same emphasis on ordinariness in Consolboard, supra, at p. 523:

The persons to whom the specification is addressed are ordinary workmen, ordinarily skilled in the art to which the invention relates and possessing the ordinary amount of knowledge incidental to that particular trade. The true interpretation of the patent is to be arrived at by a consideration of what a competent workman reading the specification at its date would have understood it to have disclosed and claimed.

[71] Ordinariness will, of course, vary with the subject matter of the patent. Rocket science patents may only be comprehensible to rocket scientists. The problem with Mr. Pielemeier is that he could not be a good guide to the common knowledge of ordinary workers in the industry because his opinions were predicated on Whirlpool’s in-house knowledge, and he made no bones about that fact.

While the hypothetical ordinary worker is uninventive, he or she is deemed to be reasonably diligent in keeping up with advances in the field to which the patent relates.

74 I think, as stated, the trial judge was wrong to have accepted the evidence of a long-time employee of the respondent Whirlpool Corporation as a proxy for the ordinary worker. However, I also conclude that he was quite entitled to reject the evidence of Mr. Mellinger as not being a sufficient factual basis to invalidate the ’734 intermittent drive claims. The trial judge was concerned, as I read his opinion, that Mr. Mellinger’s testimony was not supported by the level of practical understanding of dual action washing machines that by 1981 was common knowledge among the skilled workers who were interested in this end of the washing machine business. Dual action agitators were, after all, big news for these people in the late 1970s. While the hypothetical ordinary worker is deemed to be uninventive as part of his fictional personality, he or she is thought to be reasonably diligent in keeping up with advances in the field to which the patent relates. The common knowledge of skilled workers undergoes continuous evolution and growth. The trial judge made a finding of fact that it would be unsafe to rely on Mr. Mellinger’s evidence because he had failed to keep up to date in this respect.