Key Takeaways

  • The concept of one of ordinary skill in the art (PHOSITA) is a legal fiction used in patent law to measure non-obviousness, sufficiency of disclosure, and claim interpretation.
  • Courts weigh factors such as the type of problems in the field, prior solutions, speed of innovation, and sophistication of the technology.
  • The Supreme Court in KSR v. Teleflex emphasized that a PHOSITA is a person of ordinary creativity, not a “robotic” worker.
  • Recent USPTO guidance stresses that PHOSITA analysis should adapt to modern innovation, considering collaborative and interdisciplinary problem-solving.
  • Federal Circuit rulings confirm experts testifying about PHOSITA need not have personally held ordinary skill at the time of invention.
  • Scholars highlight that PHOSITA is not a “real” individual but a shifting benchmark that balances innovation incentives against public access to technology

A person having ordinary skill in the art is a legal construct utilized in patent law as a tool to standardize the estimation and evaluation of patentability requirements. Sometimes known as a "person skilled in the art" or abbreviated as PHOSITA, this legal parameter is used in cases of non-obviousness, interpretation of the claimed idea in the prosecution of applications, patent litigation, insufficient disclosure, and infringement proceedings.

A person skilled in the art is expected to have average knowledge, ability, and awareness in the field at that time. He or she is expected to be a skilled practitioner in the applicable field of technology. Everything in the "state of the art" should be accessible to him or her, including the cited search report documents and the means and capacity for ordinary work and experimentation related to the applicable field of technology.

If the issue causes the person skilled in the art to find a solution in another field, a specialist is the person who is able to solve the issue. Based on the specialist's ability and knowledge, a specialist can assess whether the solution requires an inventive step.

In the applicable technical field, the skilled person is engaged in continuous development. He or she may seek suggestions in related or general fields, or even in remote fields, if requested to do so. Currently, the average experience and legal definition of a claim of the person having ordinary skill in the art is not explicitly defined.

Determining Ordinary Level of Skill

A person having ordinary skill in the art is a hypothetical person who is assumed to have been aware of the relevant art at the time of the creation. Legally, there are a few factors that can be taken into consideration in order to determine the level of ordinary skill in the art as associated with patent law:

  • Type of problems encountered in the art
  • Prior art solutions to those problems
  • Rapidity with which innovations are made
  • Sophistication of technology
  • Educational level of active workers in the field

It's not necessary for every factor to be present in a case. One or more factors may be of central concern. The courts have determined some definitive conclusions in the following cases:

  • KSR Int'l Co versus Teleflex Inc., 550 U.S. 398, 421, 82 USPQ2d 1385, 1397 (2007) has determined that a person of ordinary skill in the art is also a person of ordinary creativity, not an automaton.
  • Id at 420, 82 USPQ2d at 1396 has determined that office personnel may also take into account "the interferences and creative steps that a person of ordinary skill in the art would employ."
  • The "hypothetical 'person having ordinary skill in the art' to which the claimed subject matter pertains would, of necessity have the capability of understanding the scientific and engineering principles applicable to the pertinent art."
  • Nat'l Steel Car, Ltd. v. Can. Pac. Ry., Ltd., 357 F.3d 1319, 1338, 69 USPQ2d 1641, 1656 (Fed. Cir. 2004) has determined that although a drawing made by an engineer was not prior art, it could nonetheless "be used to demonstrate a motivation to combine implicit in the knowledge of one of ordinary skill in the art."
  • Ex parte Erlich, 22 USPQ 1463 (Bd. Pat. App. & Inter. 1992) has determined that references that do not quality as prior art due to the postdate of the claimed invention may still be relied upon to show the level of ordinary skill in the art at or around the time the invention was made.
  • Ex parte Hiyamizu, 10 USPQ2d 1393, 1394 (Bd. Pat. App. & Inter. 1988): The Board did not agree with the examiner's definition of a person having ordinary skill in the art (which was a doctorate level engineer or scientist working at least 40 hours a week in semiconductor research or development), and found that the hypothetical person is not able to be defined by way of credentials, and that such evidence in the application did not support the notion that such a person would need a doctorate or equivalent knowledge or experience in science in engineering.

Expert Testimony and PHOSITA

Litigation often requires expert witnesses to explain how a PHOSITA would have understood an invention at the relevant time. Importantly, courts have clarified that an expert need not have possessed ordinary skill in the art at the time of invention to provide reliable testimony. For example, in Osseo Imaging, LLC v. Planmeca USA Inc. (Fed. Cir. 2024), the Federal Circuit affirmed that expertise acquired later can still inform the court’s understanding of what the hypothetical skilled person would have known. This flexibility ensures that expert testimony remains accessible even in rapidly evolving technical areas.

PHOSITA as a Legal Construct

While frequently described as a “skilled practitioner,” one of ordinary skill in the art is not a literal individual. Instead, courts treat PHOSITA as a legal construct that evolves with technology and case law. This construct helps judges and examiners apply an objective standard to inherently subjective questions, such as whether an invention is obvious. Academic commentary emphasizes that PHOSITA is a policy tool, ensuring that patents reward true innovation without giving undue monopolies over incremental advances.

Modern Guidance on PHOSITA

The USPTO has recently issued guidance clarifying how examiners should evaluate the level of ordinary skill in the art. Instead of focusing narrowly on formal education, the Office recognizes that today’s inventors often operate in highly interdisciplinary environments. As such, a person of ordinary skill may be expected to combine knowledge from multiple fields or to rely on collaborative approaches that were less common in earlier decades. This perspective encourages patent drafters to describe their inventions in a way that anticipates how a PHOSITA would interpret and build upon the disclosure in the context of modern innovation practices.

Frequently Asked Questions

  1. What does “one of ordinary skill in the art” mean?
    It refers to a hypothetical person with average knowledge and creativity in a relevant technical field, used as a benchmark in patent law.
  2. Why is PHOSITA important in patent cases?
    It helps determine if an invention is obvious, whether a disclosure is sufficient, and how claims should be interpreted.
  3. Does PHOSITA represent a real person?
    No. PHOSITA is a legal fiction that reflects policy goals rather than a specific individual’s actual abilities.
  4. Can experts testify about PHOSITA without having been skilled at the time of invention?
    Yes. Courts allow experts to testify even if they acquired expertise after the invention date, as long as they can reliably describe the knowledge of a PHOSITA.
  5. Has the USPTO updated its approach to PHOSITA?
    Yes. Recent guidance highlights interdisciplinary knowledge and collaborative problem-solving as factors in defining ordinary skill.

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