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Prior art (also known as state of the art, which also has other meanings, or background art), in most systems of patent law, constitutes all information that has been made available to the public in any form before a given date that might be relevant to a patent's claims of originality. If an invention has been described in the prior art, a patent on that invention is not valid.
Information kept secret, for instance, as a trade secret, is not usually prior art, provided that employees and others with access to the information are under a non-disclosure obligation. With such an obligation, the information is typically not regarded as prior art. Therefore, a patent may be granted on an invention, although someone else already knew of the invention. A person who used an invention in secret may in some jurisdictions be able to claim "prior user rights" and thereby gain the right to continue using the invention. As a special exception, earlier-filed and unpublished patent applications do qualify as prior art as of their filing date in certain circumstances.
In order to anticipate a claim, prior art is generally expected to provide a description sufficient to inform an average worker in the field (or the person skilled in the art) of some subject matter falling within the scope of the claim. Prior art must be available in some way to the public, and in many countries, the information needs to be recorded in a fixed form somehow. Prior art generally does not include unpublished work or mere conversations (though according to the European Patent Convention, oral disclosures also form prior art—see Article 54(2) EPC). It is disputed whether traditional knowledge (e.g., of medical properties of a certain plant) constitutes prior art.
Patents disclose to society how an invention is practiced, in return for the right (during a limited term) to exclude others from manufacturing, selling, offering for sale or using the patented invention without the patentee's permission. Patent offices deal with prior art searches in the context of the patent granting procedure.
Usage in litigation 
Arguments claiming prior art are used both in defending and attacking patent validity. In one U.S. case on the issue, the court said:
- "One attacking the validity of a patent must present clear and convincing evidence establishing facts that lead to the legal conclusion of invalidity. 35 U.S.C. § 282. To establish invalidity under 35 U.S.C. § 103, certain factual predicates are required before the legal conclusion of obviousness or nonobviousness can be reached. The underlying factual determinations to be made are
- (1) the scope and content of the prior art;
- (2) the differences between the claimed invention and the prior art;
- (3) the level of ordinary skill in the art; and
- (4) objective evidence of non-obviousness, such as commercial success, long-felt but unsolved need, failure of others, copying, and unexpected results."
- Graham v. John Deere Co., 383 U.S. 1, 17, 148 USPQ 459, 467 (1966).
Types of prior art searches 
A "novelty search" is a prior art search that is often conducted by patent attorneys, patent agents or professional patent searchers before an inventor files a patent application. A novelty search helps an inventor to determine if the invention is novel before the inventor commits the resources necessary to obtain a patent. The search may include searching in databases of patents, patent applications and other documents such as utility models and in the scientific literature. A search of this type is also conducted by patent examiners during prosecution of the patent application. For instance, examiner's search guidelines applicable to the United States are found in the U.S. Manual of Patent Examining Procedure (MPEP) 904.02 General Search Guidelines, Prior Art, Classification, and Search.
A "validity search" is a prior art search done after a patent issues. The purpose of a validity (or invalidity) search is to find prior art that the patent examiner overlooked so that a patent can be declared invalid. This might be done by an entity infringing, or potentially infringing, the patent, or it might be done by a patent owner or other entity that has a financial stake in a patent to confirm the validity of a patent. Crowdsourcing, where a large number of interested people search for prior art, may be effective where references would otherwise be difficult to find.
A clearance search is a search of issued patents to see if a given product or process violates someone else's existing patent. If so, then a validity search may be done to try to find prior art that would invalidate the patent. A clearance search is a search targeting patents being in force and may be limited to a particular country and group of countries, or a specific market.
Duty of disclosure 
In the United States, inventors and their patent agents or attorneys are required by law to submit any references they are aware of to the United States Patent and Trademark Office that may be material to the patentability of the claims in a patent application they have filed. The patent examiner will then determine if the references qualify as "prior art" and may then take them into account when examining the patent application. If the attorney/agent or inventor fails to properly disclose the potentially relevant references they are aware of, then a patent can be found invalid for inequitable conduct.
Australia has abolished its duty of disclosure with regard to the results of documentary searches by, or on behalf of, foreign patent offices, except where:
- (a) normal exam was requested before April 22, 2007,
- (b) the foreign patent office search issued before April 22, 2007, and
- (c) acceptance (allowance) was officially advertised before July 22, 2007.
Public participation in patent examination 
With the advent of the Internet, a number of initiatives have been undertaken to create a forum where the public at large can participate in prior art searches. These forums have been related to both issued patents and pending patent applications.
Pending patent applications 
More recently, different attempts to employ open Internet-based discussions for encouraging public participation commenting on pending U.S. applications have been started. These may take the form of a wiki:
- Peer-to-patent online system for open, community patent review.
- Wikipatents. Public patent clarity: the public can add prior art references for a given patent.
Patent examiners often use the online encyclopedia Wikipedia as a reference to get an overall feel for a given subject. Citations of Wikipedia as actual prior art can be problematic, however, due to the fluid and open nature of its editing, and Patents Commissioner Doll said the agency used Wikipedia entries as background and not as a basis for accepting or rejecting an application.
See also 
- Defensive publication
- Illegal number, illegal prime
- Information disclosure statement (IDS)
- Internet as a source of prior art
- Non-binding opinion (United Kingdom patent law)
- Patent classification
- Patent watch
- Priority right
- Public participation in patent examination
- Search report
Notable prior art databases 
- Espacenet—European Patent Office public prior art database.
- Google Patents—search engine from Google that indexes patents from the United States Patent and Trademark Office (USPTO)
For other patent search services, see Category:Patent search services.
- "The expression 'background art' ... must have the same meaning as the more familiar expression 'prior art'" in EPO Board of appeal decision T 11/82 of 15 April 1983, Headnote II and Reasons 15.
- See for example Article 54(2) EPC and 35 U.S.C. § 102
- Graham v. John Deere Co. of Kansas City, 383 US 1, Sup. Ct., 1966.
- Tokai Corp. v. Easton Enterprises, Inc., 632 F. 3d 1358 at 1363-64, Ct. App. (Fed. Cir.), 2011.
- USPTO, Manual of Patent Examining Procedure, General Search Guidelines [R-3] - 900 Prior Art, Classification, and Search, July 2010.
- Nowotarski, Mark (July 2012). "Patent Invalidity Search". Insurance IP Bulletin. Retrieved March 1, 2013.
- Therasense, Inc. v. Becton, Dickinson and Co., 649 F. 3d 1276, Ct. App. (Fed. Cir.), 2011.
- Patent e-Bulletin, Summer '2002 Developments: Following The United States, Japan And Australia Enact Duty Of Disclosure Requirements, Gastle & Associates (through archive.org)
- See also Japan's Examination Guidelines for Patent and Utility Model in Japan, Examination Standards Office, December 2011; and Japan's Right Obtainment Procedures.
- Japan Patent Office, Publication of the "Examination Guidelines on Requirement for Disclosure of Information on Prior Art Documents", Last updated 30 August 2002.
- Australian Patent Office Manual of Practice and Procedure, 2.13.10 Considering Subsection 45(3) Search Results, 2011-08-15.; see also Changes to regulations made under sections of the Patents Act 1990, (sections 27(1), 45(3) and 101D) Australian Official Journal of Patents, 2007-11-01.
- Office of the Chief Information Officer, Secure Application Development Coding Policy OCIO, USPTO, May 22, 2009.
- USPTO Bans Wikipedia, The Patent Librarian's Notebook, 2006-09-10, citing Stead, Deborah, Up Front: Kicking Wiki Out Of The Patent Office, Bloomberg Business Week, 2006-09-04.
Further reading 
- Blenko, Walter J., Considering What Constitutes Prior Art in the United States, JOM, 43 (6) (1991), p. 45. Retrieved 2012-01-27.
Official institutions 
- WIPO (World Intellectual Property Organization)
- USPTO The U.S. Patent and Trademark Office.
- USPTO.gov, free access to US patents.
- Patent Application Information Retrieval (PAIR), the USPTO search engine for patent and patent application file histories displays reasons why patents are issued; search by application number or customer number.
- Seven Step Strategy, USPTO patent search strategy.
- EPO (European Patent Office)