Person having ordinary skill in the art  

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Train wreck at Montparnasse (October 22, 1895) by Studio Lévy and Sons.
Train wreck at Montparnasse (October 22, 1895) by Studio Lévy and Sons.

The person having ordinary skill in the art (often abbreviated PHOSITA in the United States), the person of ordinary skill in the art, the skilled addressee, person skilled in the art or simply the skilled person is a legal fiction found in many patent laws throughout the world. This fictional person is considered to have the normal skills and knowledge in a particular technical field, without being a genius. He or she mainly serves as a reference for determining, or at least evaluating, whether an invention is non-obvious or not (in US patent law), or does involve an inventive step or not (in European patent laws). If it would have been obvious for this fictional person to come up with the invention while starting from the prior art, then the particular invention is considered not patentable.

In some patent laws, the person skilled in the art is also used as a reference in the context of other criteria, for instance in order to determine whether an invention is sufficiently disclosed in the description of the patent or patent application (sufficiency of disclosure is a fundamental requirement in most patent laws), or in order to determine whether two technical means are equivalents when evaluating infringement (see also doctrine of equivalents).

In practice, this legal fiction is a set of legal fictions which evolved over time and which may be differently construed for different purposes. It may be said that this legal fiction basically translates the need for each invention to be considered in the context of the technical field it belongs to.


United States

A person having ordinary skill in the art is a legal fiction defined in the Patent Act of the United States. The PHOSITA is a test of "obviousness" which is one of the largest gray areas in patent law.

A patent may not be obtained though the invention ... if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art to which said subject matter pertains. Patentability shall not be negatived by the manner in which the invention was made. (35 U.S.C. § 103 (A))


Quite similar to the logic of "reasonable person" used in the common law of torts as a test of negligence, the PHOSITA is a hypothetical individual, neither a genius nor a layperson, created in the mind of a patent examiner or the jury to see if a claimed invention is too obvious to be patented.


During the examination of a patent application, the examiner tries to find out if that invention has already been invented by another person. If so, the patent application will be returned to the applicant to be narrowed or modified. If not, the examiner will bring out the PHOSITA test to check if that invention is so obvious that people in the trade will invent it with or without patent applicant's efforts. In the end, if the examiner can not discover a piece of prior art that may lead the PHOSITA to the invention, the United States Patent and Trademark Office (USPTO) is required by statute to award that applicant a patent.

It is well known that it may take a few months or a couple of years for a paper to be published in a peer reviewed academic journal. The date of a sanctioned prior art can be a little later than the patent's application date:

Examiner properly relied upon prior art publication in rejecting claims for production of [certain antibodies] ... under [35 U.S.C. § 103], even though publication itself is not prior art against present claims, since publication establishes level of ordinary skill in art at and around time of present invention. Ex parte Erlich, 22 USPQ.2d 1463 (Bd.Pat.App. & Inter. 1992).


The term "ordinary skill" is not rigidly defined. The requirements of a nuclear physicist of ordinary skill are surely different from a chef of ordinary skill. An invention that involves aerodynamics takes a different kind of "ordinary skill" from another that involves woodworking.

Factors that may be considered in determining level of ordinary skill in the art include
  1. the educational level of the inventor;
  2. type of problems encountered in the art;
  3. prior art solutions to those problems;
  4. rapidity with which innovations are made;
  5. sophistication of the technology; and
  6. educational level of active workers in the field.
Environmental Designs, Ltd. v. Union Oil Co., 713 F.2d 693, 696, 218 USPQ 865, 868 (Fed. Cir. 1983), cert. denied, 464 U.S. 1043 (1984).

KSR v. Teleflex

The Supreme Court reversed a decision by the Court of Appeals for the Federal Circuit based on how the lower court defined the capabilities of a PHOSITA. KSR v. Teleflex was decided by a unanimous Supreme Court on April 30, 2007.

Importantly, Justice Kennedy opinion stated, "A person of ordinary skill is also a person of ordinary creativity, not an automaton." Although the Court's opinion acknowledged other Federal Circuit cases that described a PHOSITA as having "common sense" and who could find motivation "implicitly in the prior art," Kennedy emphasized that his opinion was directed at correcting the "errors of law made by the Court of Appeals in this case" and does not necessarily overturn all other Federal Circuit precedent.

Once the PHOSITA is properly defined, KSR v. Teleflex described how obviousness should be determined:

In determining whether the subject matter of a patent claim is obvious, neither the particular motivation nor the avowed purpose of the patentee controls. What matters is the objective reach of the claim. If the claim extends to what is obvious, it is invalid under §103. One of the ways in which a patent's subject matter can be proved obvious is by noting that there existed at the time of invention a known problem for which there was an obvious solution encompassed by the patent's claims.

which was applied to the facts before the Court with the following:

The proper question to have asked was whether a pedal designer of ordinary skill, facing the wide range of needs created by developments in the field of endeavor, would have seen a benefit to upgrading Asano with a sensor.

Software patents

One of the frequent criticisms of software patents is the large number of patents which seem to violate the PHOSITA standard, but which are nevertheless granted by the US Patent Office and other countries' patent offices.Template:Fact

European Patent Convention

The European Patent Convention states in its Template:EPC Article that "an invention shall be considered as involving an inventive step if, having regard to the state of the art, it is not obvious to a person skilled in the art."


Practically all patent legislations disallow the patentability of something obvious. Hence, it is no surprise that the laws of other countries have similar formulations.

For example, the German Patent Act (Patentgesetz) requires that the invention "cannot be derived by a Fachmann from the state of the art in an obvious manner".<ref>("... wenn sie sich für den Fachmann nicht in naheliegender Weise aus dem Stand der Technik ergibt.", Art. 4 of the Patentgesetz).</ref>

The word Fachmann (an ordinary German word meaning somebody who has professional knowledge in a field) is made specific by ständiger Rechtsprechung (usual court opinion) as a "specialist with average knowledge and talent whom one would ordinarily ask to seek a solution for the (objective) problem the invention deals with"<ref>"Sachverständiger mit durchschnittlichem Wissen und Können, den man üblicherweise mit der Lösung der (objektiven) Aufgabe der Erfindung betrauen würde" (stRspr - BPatG Mitt. 84, 213, T 32/81 Abl. 1982, 225)</ref>

Incomplete implementations of the obviousness test

Patent examination is a costly and time consuming process. In many small countries or jurisdictions such as Singapore and Hong Kong, a patent may be issued based on a prior art search report made by a sanctioned international searching authority. Even though these patents were not prosecuted before issue, in case the patentee files a lawsuit against an accused infringer, the patent's validity will still be tested for its obviousness in the court.

Unless indicated otherwise, the text in this article is either based on Wikipedia article "Person having ordinary skill in the art" or another language Wikipedia page thereof used under the terms of the GNU Free Documentation License; or on original research by Jahsonic and friends. See Art and Popular Culture's copyright notice.

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