A person having ordinary skill in the art (abbreviated PHOSITA), a person of (ordinary) skill in the art (POSITA or PSITA), a person skilled in the art, a skilled addressee or simply a skilled person is a legal fiction found in many patent laws throughout the world. This hypothetical person is considered to have the normal skills and knowledge in a particular technical field (an "art"), without being a genius. This measure mainly serves as a reference for determining, or at least evaluating, whether an invention is non-obvious or not (in U.S. patent law), or involves 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. This legal fiction basically translates the need for each invention to be considered in the context of the technical field it belongs to.
Canada
The Patent Act (R.S.C., 1985, c. P-4) makes explicit reference to a "person skilled in the art" in the s. 28.3 requirement that the subject matter of a patent be non-obvious.
The person skilled in the art is described in Beloit Canada Ltd. v. Valmet Oy: 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.
European Patent Convention
The European Patent Convention (EPC) refers to the skilled person in and provides for 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".
The EPC also refers to the skilled person in , which requires that "[t]he European patent application must disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art".
Still further, the Protocol on the Interpretation of refers to the skilled person. Article 1, 2nd sentence, states that "[n]or should it [Article 69 EPC] be taken to mean that the claims serve only as a guideline and that the actual protection conferred may extend to what, from a consideration of the description and the drawings by a "person skilled in the art", the patent proprietor has contemplated".
The European Patent Office provides guidelines that set forth some of the skilled person's capabilities.
A related concept is the "business person", who is also a notional person. It is used at the EPO when assessing inventive step of an invention involving both technical and non-technical elements. The business person "represents an abstraction or shorthand for a separation of business considerations from technical".
United States
A person having ordinary skill in the art is a legal fiction first codified in the Patent Act of 1952. The PHOSITA is a test of "obviousness" which is one of the largest gray areas in patent law.
The PHOSITA appears again in slightly different words in the provision requiring a proper disclosure:
Comparison
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.