A patent grants the patent holder the exclusive right to exclude others from making, using, importing, and selling the patented innovation for a limited period of time.  The U.S. Patent Act, 35 U.S.C. §§ 1 et seq., was enacted by Congress under its Constitutional grant of authority to secure for limited times to inventors the exclusive right to their discoveries. See Article I, Section 8, Clause 8

Granting exclusive rights to the inventor is intended to encourage the investment of time and resources into the development of new and useful discoveries.  In exchange for this limited monopoly, immediate disclosure of the patented information to the U.S. Patent and Trademark Office (PTO) is required.  Once the term of protection has ended, the patented innovation enters the public domain.

Requirements for Patentability

The five primary requirements for patentability are: (1) patentable subject matter, (2) utility, (3) novelty, (4) nonobviousness, and (5) enablement.

Patentable Subject Matter

The patentable subject matter requirement addresses the issue of which types of inventions will be considered for patent protection.  Under 35 U.S.C. § 101, the categories for patentable subject matter are broadly defined as any process, machine, manufacture, or composition of matter, or improvement thereof.  In Diamond v. Chakrabarty, the Supreme Court found that Congress intended patentable subject matter to "include anything under the sun that is made by man."  See Diamond v. Chakrabarty, 447 U.S. 303 (1980).  However, the Court also stated that this broad definition has limits and does not embrace every discovery.  According to the Court, the laws of nature, physical phenomena, and abstract ideas are not patentable.  The relevant distinction between patentable and unpatentable subject matter is between products of nature, living or not, and human-made inventions.

The traditional rules that "printed matter" and "business methods" are unpatentable have recently been called into question.  In 1998, the Federal Circuit held that a system of conducting business can be patentable as a process even though it does not act on anything tangible.  See State Street Bank & Trust Co. v. Signature Financial Group, 149 F.3d 1368 (Fed. Cir. 1998).  The rule against patenting printed matter still retains its force, although printed matter may be patentable if its relationship with the physical invention is either new and useful, or new and non-obvious.


The second requirement for patentability is that the invention be useful.  See 35 U.S.C. § 101.  The PTO has developed guidelines for determining compliance with the utility requirement.  The guidelines require that the utility asserted in the application be credible, specific, and substantial.  These terms are defined in the Utility Guidelines Training Materials.  Credible utility requires that logic and facts support the assertion of utility, or that a person of ordinary skill in the art would accept that the disclosed invention is currently capable of the claimed use.  The utility must be specific to the subject matter claimed; not a general utility that could apply to a broad class of inventions.  Substantial utility requires that the invention have a defined real world use; a claimed utility that requires or constitutes carrying out further research to identify or confirm a use in the context of the real world is not sufficient.


The novelty requirement described under 35 U.S.C. § 102 consists of of two disctinct requirements; novelty and statutory bars to patentability.  Novelty requires that the invention was not known or used by others in this country, or patented or described in a printed publication in this or another country, prior to invention by the patent applicant.  See 35 U.S.C. § 102(a).  To meet the novelty requirement, the invention must be new compared to the prior art.  The statutory bar applies where the invention was in public use or on sale in this country, or patented or described in a printed publication in this or another country more than one year prior to the date of the application for a U.S. patent.  See 35 U.S.C. § 102(b).  In other words, the right to patent is lost if the inventor delays too long before seeking patent protection.  An essential difference between the novelty requirement and statutory bars is that an inventor's own actions cannot destroy the novelty of his or her own invention, but can create a stutory bar to patentability.


Congress added the nonobviousness requirement to the test for patentability with the enactment of the Patent Act of 1952.  The test for nonobviousness is whether the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious to a person having ordinary skill in the art at the time the invention was made.  See 35 U.S.C. § 103

The Supreme Court first applied the nonobviousness requirement in Graham v. John Deere Co., 383 U.S. 1 (1966).  The Court held that nonobviousness could be determined through basic factual inquiries into the scope and content of the prior art, the differences between the prior art and the claims at issue, and the level of skill possessed by a practioner of the relevant art. 

In 2007, the Supreme Court again addressed the test for nonobviousness.  See KSR International Co. v. Teleflex, Inc. (04-1350).  In KSR, the Court rejected the test for nonobviousness employed by the Court of Appeals for the Federal Circuit as being too rigid.  Under the "teaching, suggestion, or motivation test" applied by the Federal Circuit, a patent claim was only deemed obvious if "some motivation or suggestion to combine the prior art teachings can be found in the prior art, the nature of the problem, or the knowledge of  person having ordinary skill in the art."  The Court endorsed a more expansive and flexible approach under which "a court must ask whether the improvement is more than the predictable use of prior art elements according to their established functions."


The enablement requirement is directly related to the specification, or disclosure, which must be included as part of every patent application.  "The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention."  See 35 U.S.C. § 112.  At the end of the specification, the applicant lists "one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention."  See 35 U.S.C. § 112.  Enablement is understood as encompassing three distinct requirements:  the enablement requirement, the written description requirement, and the best mode requirement.   

Every patent application must include a specification describing the workings of the invention, and one or more claims at the end of the specification stating the precise legal definition of the invention.  To satisfy the enablement requirement, the specification must describe the invention with sufficient particularity that a person having ordinary skill in the art would be able to make and use the claimed invention without "undue experimentation."  See In re Wands, 858 F.2d 731 (Fed Cir. 1988).  In In re Wands, the Federal Circuit Court of Appeals listed eight factors to be considered in determining whether a disclosure would require undue experimentation.  The Patent and Trademark Office has incorporated these factors in the Manual of Patent Examining Procedure.  See MPEP 2164.01(a)

The written description requirement compares the description of the invention set out in the specification with the particular attributes of the invention identified for protection in the claims.  It is possible for a specification to meet the test for enablement, but fail the written description test.  The basic standard for the written description test is that the applicant must show he or she was "in possession" of the invention as later claimed at the time the application was filed.  Any claim asserted by the inventor must be supported by the written description contained in the specification.  The goal when drafting patent claims is to make them as broad as the PTO will allow.  THe writing requirement imposes two important limitations: the applicant may not seek protection for a claim that is broader than the supporting specification; and, if the applicant intends to focus on a particular attribute of the invention in the claims, that attribute must be clearly indicated in the specification. 

In addition to disclosing sufficient information to enable others to practice the claimed invention, the patent applicant is required to disclose the best mode of practicing the invention.  See 35 U.S.C. § 112.  The best mode requirement is violated where the inventor fails to disclose a preferred embodiment, or fails to disclose a preference that materially affects making or using the invention.  See Bayer AG v. Schein Pharmaceuticals, Inc., 301 F.3d 1306 (Fed. Cir. 2002).  A violation of the best mode requirement involves two essential elements:  first, it must be determined whether the inventor actually had a preferred mode of practicing the invention at the time the application was filed; if it is established that the inventor did contemplate a best mode for practicing the invention, the question becomes whether sufficient information was disclosed to enable a person of ordinary skill in the art to practice the best mode of the invention. 

Patent Application Process

Patents are granted and issued through the U.S. Patent and Trademark Office (PTO).  See 35 U.S.C. §§ 1-26.  The rules of practice in patent cases are listed in Title 37, Part I, of the Code of Federal Regulations.  The process by which a patent is obtained from the PTO is called "prosecution."  Prosecution begins when a patent application is filed with the PTO.  The basic elemements of a patent application are:  the specification, including a summary of the invention usually accompanied by drawings; one or more claims listed at the end of the specification; an oath or declaration that the inventor was the first to invent the subject matter described in the specification; and applicable filing fees.

Each patent application received by the PTO is examined by a patent examiner in the order it is received.  The patent examiner is required to thoroughly study the patent application and investigate the available prior art. See 37 C.F.R. § 1.104.  Once the examination is complete, the examiner may accept the application and issue a patent; issue a rejection of some or all of the claims made in the application; or issue an objection if a problem with the form of the application is detected.  If a claim is rejected as unpatentable, or an objection to the form of the application is issued, the examiner must notify the applicant, stating the reasons for each rejection or objection and providing information and references to assist the applicant in judging the propriety of continuing the prosecution.  See 37 C.F.R. § 1.104; 35 U.S.C. § 132.

Upon receiving notice of any objections or rejections issued by the PTO, the applicant is entitled to a reexamination of the application whether or not the application has been amended to address the reasons stated by the examiner.  See 35 U.S.C. § 132.  If the application is rejected a second time, or a final rejection is issued, the applicant may file an appeal of the decision with the Board of Patent Appeals and Interferences.  See 35 U.S.C. § 134.  An applicant who is dissatisfied with the decision of the Board of Patent Appeals and Interferences has a choice between two further options for appeal.  The applicant may either appeal the Board's decision to the United States Court of Appeals for the Federal Circuit under 35 U.S.C. § 141, or pursue a civil action to obtain patent under 35 U.S.C. § 145 by filing against the Director in the United States District Court for the District of Columbia. 

In 1975, the Patent Act was amended to accomodate the Patent Cooperation Treaty (PCT).  See 35 U.S.C. §§ 351-376.  The PCT permits applicants from signatory countries to wait for up to 30 months after the initial filing of a patent application in one country before beginning a full prosecution of the patent in other countries.  The PCT gives the inventor the benefit of extra time to assess the technical merits and commercial potential of the invention, and to decide in which countries patent protection will be sought prior to the expenditure of filing and examination fees.

Rights of a Patent Owner

The patent owner is granted the exclusive right to prevent others from making, using, offering for sale, or selling the patented invention. See 35 U.S.C. § 154.  Prior to the Agreement on Trade-Related Aspects of Intellectual Property (TRIPS) accompanying the Uruguay Round GATT, patents were issued for a non-renewable period of seventeen years, measured from the date of issuance.  Under current statutory provisions, the term of protection for utility patents is twenty years measured from the date of filing (35 U.S.C. § 154), with extensions of up to five years permitted for drugs, medical devices, and additives (35 U.S.C. § 156).  The current term of protection for design patents is fourteen years from the date of filing.  See 35 U.S.C. § 173

A long-established doctrine of patent law, the exhaustion doctrine, entitles a patentee to a single royalty per patented device. This rule aims to prevent patentees from collecting a series of royalty payments for a single invention. The Supreme Court affirmed this rule in its 1942 decision, United States v. Univis Lens Co., 316 U.S. 241.  In 2008, the U.S. Supreme Court reconsidered the contemporary relevance of the doctrine in Quanta Computers v. LG Electronics (06-937).  In a unanimous decision, the Court reaffirmed the doctrine, holding that the exhaustion doctrine prevents a patentee from bringing an action against a third party purchaser after having already received a royalty payment from the initial sale.


Patents are exclusively governed by federal law; the federal disctrict courts have original jurisdiction of all civil cases arising under any federal law relating to patents. See 28 U.S.C. § 1338.  In 1982, the United States Court of Appeals for the Federal Circuit assumed the jurisdiction of the former U.S. Court of Patent and Customs Appeals.  Appeals from district court decisions related to patent law are now reviewed by the Federal Circuit.

Once a patent has been issued, the patent owner may bring a lawsuit against anyone accused of infringing the patent.  There are two primary defenses to patent infringement:  the patent is invalid; and even if the patent is valid, the products being made or sold do not infringe the patent.  The Patent Act provides that an issued patent is presumed valid, and the burden of establishing that a patent is invalid rests with the person asserting its invalidity.  See 35 U.S.C. § 282.  Independent invention is not a defense to patent infringement.  A person who reasonably fears being sued for patent infringement may file suit for a declaratory judgment that the patent at issue is invalid, or that the conduct in question does not consitute infringement.

In 2007, the U.S. Supreme Court in MedImmune v. Genetech (05-608) held that a patent licensee does not have to breach the terms of the contract in order to meet the actual controversy requirement and challenge the licensed patent in court.

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Category: Intellectual Property