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What is a Prior Art Search

March 13 2019

In its simplest terms, a patent is a legal construct that grants to inventors the rights to exclusively practice an invention in the United States for a period of time (currently 20 years from the filing date of a patent application).  In the United States, patents are to be granted only for inventions which are not only useful, but also novel and non-obvious in light of the prior art.

Novelty and non-obvious of an invention is determined based on prior art. The term “prior art,” as it is used in the United States, refers to any information that is available to the public in any form prior to the filing of a patent application.

What is a Prior Art Search?

Simply put, a prior art search involves searching various publicly available sources to find out whether an invention has been previously described or detailed in other references (i.e., prior art). If an invention has been described in a prior art reference, a later filed patent application would not be granted as being anticipated by the prior art. In short, if there is a publication dated before the filing date of the patent application, and that publication describes all aspects of the invention as claimed, the invention is not novel, and therefore ineligible for patent protection.

The most obvious form of prior art is previously granted patents and published patent applications.  But even without a previously filed patent application, an existing product on the market that patent protection was never filed for is also prior art.  But this is not where the concept ends. A piece of technology that is centuries old can be prior art. A previously described idea that could not possibly work under the existing technologies of the time can be prior art[i]. Anything can be prior art. The sources of prior art include patents, published patent applications, periodicals, books, and products. However, the most common prior art used by Examiners at the United States Patent and Trademark Office (USPTO), by far, are previously granted patents and patent publications.

Types of Prior Art Search

Prior art searches take four forms: novelty, validity, clearance and landscape searches.

  • A novelty search helps an inventor to determine if the invention is novel before the inventor commits the resources necessary to obtain a patent and is done before an inventor files a patent application.
  • A validity search is done after patent issues, the purpose of which is to find prior art that the patent office overlooked. These can be useful for competitors looking to contest the validity of a granted patents.
  • A clearance search is a search of issued patents to see if a given product or process violates someone else’s existing or pending patent(s).
  • A landscape search provides a high-level view of the technology space and is normally performed to understand the lay of the land when entering a new technological area, including recent trends in technology, competitors, filing activity, and white-space/adjacent technologies.

Why Is Prior Art Search Important?

Prior art is important because it controls the ability to gain intellectual property (IP) rights over an invention. If the inventor is unable to gain IP rights, the invention may have a decreased market value, as the inventor may be unable to prevent competitors from entering the market, or be forced to obtain licenses from existing IP rights holders.

Furthermore, except where the inventor is a subject matter expert in the field of an invention and has a great deal of knowledge of industry trends and direction, without a prior art search, an inventor will be operating in an information vacuum and will not be able to form an educated opinion about whether the inventor can obtain a patent on the invention. A prior art search is therefore important to:

  • Avoid submitting patent applications with claims that are not patentable or that would easily be rejected;
  • Determine whether an invention is novel and non-obvious compared to public prior art;
  • Develop a strong patent claim strategy before filing a patent application (and reduce the chance of extensive amendments);
  • Account for close prior art when drafting your patent application. For example, you might want to describe advantages or improvements over relevant prior art, as this can help persuade the patent office that your invention is “non-obvious”;
  • Understand how your idea fits into the technological field;
  • Be better prepared to discuss your invention;
  • Look out for people who might someday infringe on the idea;
  • Look for inventions that you might accidentally infringe on the invention;
  • Find out how strong an idea is;
  • Save money by detecting existing developments;
  • Show you the best partners with whom you can collaborate;
  • Detect the latest publications in a research field and keep up-to-date on the progress made by others;
  • to assess the strength of a patented invention;
  • to acquire statistical analysis on the most innovative companies in a field;
  • to cancel a granted patent used against you by detecting new invalidating prior art that has not been considered in the patent grant process, etc.

Does Prior Art Automatically Disqualify?

Not all prior art disqualifies an invention from being able to receive a patent. Prior art essentially refers to the entire span of human knowledge, and if one effectively differentiated an invention even from a similar one, a patent may be secured.  A patent cannot be obtained in the following situations:

  • The invention or a very similar one (i.e., obvious in light of the prior art or otherwise anticipated by the prior art) has been patented anywhere else in the world;
  • The invention has been previously described anywhere in the world in a printed publication;
  • The invention or something substantially similar is public knowledge, or well-understood, routine, and conventional in the art, even if not published or patented; and
  • The invention has been publicly used, demonstrated, or offered up for sale by the inventor over one year prior to a U.S. application filing.

When Does Prior Art Not Count?

There are exceptions to prior art in which it may not count against filing a patent application. Certain experimental public uses might not count as demonstration or revelation. If an invention was secret and remained secret up until being abandoned by the original inventor, it may not apply as prior art. Trade secrets are not usually prior art, provided that employees and others with access to the information are under a non-disclosure obligation. Prior art generally does not include unpublished work or limited conversations.

However, it is important to be as careful as possible when having conversations with those not under an obligation of confidentiality.  In Medtronic v. Barry, the Court of Appeals for the Federal Circuit noted: The determination of whether a document is a “printed publication” under 35 U.S.C. § 102(b) “involves a case-by-case inquiry into the facts and circumstances surrounding the reference’s disclosure to members of the public.” For example, in Massachusetts Institute of Technology v. AB Fortia (MIT), a paper that was orally presented at a conference to a group of cell culturists interested in the subject matter was considered a “printed publication.” 774 F.2d 1104, 1109 (Fed. Cir. 1985). In that case, between 50 and 500 persons having ordinary skill in the art were told of the existence of the paper and informed of its contents by the oral presentation. Medtronic, Inc. v. Barry, 891 F.3d 1368 (Fed. Cir. Jun. 11, 2018)

Prior Art Searches and Lawsuits

If someone sues you because they think you infringed on their patent, a prior art search can help. You can conduct a prior art search in order to identify prior art that could be used to invalidate their patent, whether at trial or via an action before the USPTO. If their patent is found invalid, then they do not have grounds to maintain a suit for patent infringement.

What to invest in a prior art search?

The amount of effort spent in performing a prior art search should be proportional to the value of the invention and subsequent patent if the application is pursued to completion. A patent application filed for marketing purposes with no real intention of prosecuting until completion will not require much or any prior art searching. On the other hand, if an invention is the cornerstone of a company’s strategy, or if the field of the invention has a costly barrier to entry, a comprehensive prior art search may be warranted. As always, it should be the business goals that inform the IP strategy and the specific decisions made.


In many cases, it may be advisable for inventors to conduct a prior art search with an eye toward both the technical features of the invention and the legal aspects of patentability, such as novelty and non-obviousness. A patent or patent application is not just a technical paper; it is also a legal document. Therefore, while familiarity with the technology is mandatory for a technical prior art search, a search will yield the most value if one has an understanding of IP law—specifically, patent law as it relates to validity and infringement.

[i] We are aware of a European patent application for a new bicycle that was rejected based on a 19th Century French manuscript that detailed nearly the same bicycle, but it would not work as described at the time, as the materials of the era were too heavy or too brittle to function.  The only difference between the old bicycle and the new, was the use of carbon fiber materials, which were light enough and strong enough to make the bicycle work.  The examiner submitted that the change of materials was an obvious change, noting the entire structure of the invention was substantially the same otherwise.