Patent Prosecution

What is patent prosecution?

Patent prosecution is the stage between the filing of a patent application and its final disposition. At the conclusion of patent prosecution, a patent application may be allowed to issue as a valid U.S. patent, receive a final rejection, or be abandoned. During prosecution, a patent examiner may compare the patent application with references included in the prior art to determine whether the subject matter of the application is patentable. Typically, the patent examiner will reject at least part of the patent application as lacking novelty or being obvious in light of existing prior art. These concepts will be discussed in greater detail below.

What happens at the start of patent prosecution?

Prior to focusing on specific statutory requirements, USPTO personnel must begin examination by determining what, precisely, the applicant has invented and is seeking to patent, and how the claims relate to and define that invention. As the courts have repeatedly reminded the USPTO: “The goal is to answer the question ‘What did applicants invent?'” USPTO personnel will review the complete specification, including the detailed description of the invention, any specific embodiments that have been disclosed, the claims and any specific, substantial, and credible utilities that have been asserted for the invention. After obtaining an understanding of what applicant invented, the examiner will conduct a search of the prior art and determine whether the invention as claimed complies with all statutory requirements.

How does the examiner initially examine the claims?

The claims define the property rights provided by a patent, and thus require careful scrutiny. The goal of claim analysis for an examiner is to identify the boundaries of the protection sought by the applicant and to understand how the claims relate to and define what the applicant has indicated is the invention. USPTO personnel must first determine the scope of a claim by thoroughly analyzing the language of the claim before determining if the claim complies with each statutory requirement for patentability.

USPTO personnel should begin claim analysis by identifying and evaluating each claim limitation. For processes, the claim limitations will define steps or acts to be performed. For products, the claim limitations will define discrete physical structures or materials. Product claims are claims that are directed to either machines, manufactures or compositions of matter.

Once the examiner has carefully reviewed the claims, what comes next?

Prior to evaluating the claimed invention for compliance with the statutory requirements, an examiner will conduct a thorough search of the prior art. Generally, a thorough search involves reviewing both U.S. and foreign patents and nonpatent literature. In many cases, the result of such a search will contribute to USPTO personnel’s understanding of the invention. Both claimed and unclaimed aspects of the invention described in the specification should be searched if there is a reasonable expectation that the unclaimed aspects may be later claimed.

In determining patentability, what criteria do the examiners consider?

Once a patent examiner has determined what has been invented, and after the prior art search has been conducted, the examiner will determine whether the invention complies with the statutory requirements. To satisfy these requirements, an invention must be useful, novel, nonobvious, and disclosed such to enable a person of skill in the art to make or practice the invention. An examiner will pay close attention to claims of the patent to determine what protections the application is requesting. The examiner will also consider the written description for the clearest explanation of the applicant’s invention. The written description should exemplify the invention, explaining how it relates to the prior art and explaining the relative significance of various features of the invention.

The burden is on the USPTO to set forth a prima facie case of unpatentability. Therefore if USPTO personnel determine that it is more likely than not that the claimed subject matter falls outside all of the statutory categories, they must provide an explanation. For example, a claim reciting only a musical composition, literary work, compilation of data signal, or legal document (e.g., an insurance policy) per se does not appear to be a process, machine, manufacture, or composition of matter. If USPTO personnel can establish a prima facie case that a claim does not fall into a statutory category, the patentability analysis does not end there. USPTO personnel must further continue with a statutory subject matter analysis. Also, USPTO personnel must still examine the claims for compliance with 35 U.S.C. 102 (novelty), 103 (nonobviousness), and 112.


Section 101 of title 35, United States Code, provides:

Whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefor, subject to the conditions and requirements of this title.

As the Supreme Court has recognized, Congress chose the expansive language of 35 U.S.C. 101 so as to include “anything under the sun that is made by man” as statutory subject matter. 35 U.S.C. 101 defines four categories of inventions that Congress deemed to be the appropriate subject matter of a patent: processes, machines, manufactures and compositions of matter. The latter three categories define “things” or “products” while the first category defines “actions” (i.e., inventions that consist of a series of steps or acts to be performed). See 35 U.S.C. 100(b) (“The term ‘process’ means process, art, or method, and includes a new use of a known process, machine, manufacture, composition of matter, or material.”).

The subject matter courts have found to be outside of, or exceptions to, the four statutory categories of invention is limited to abstract ideas, laws of nature and natural phenomena. While this is easily stated, determining whether an applicant is seeking to patent an abstract idea, a law of nature or a natural phenomenon has proven to be challenging. These three exclusions recognize that subject matter that is not a practical application or use of an idea, a law of nature or a natural phenomenon is not patentable. Historically, the Supreme Court has further held in landmark cases that an “idea of itself is not patentable, but a new device by which it may be made practically useful is” and “while a scientific truth, or the mathematical expression of it, is not patentable invention, a novel and useful structure created with the aid of knowledge of scientific truth may be.” The courts have also held that a claim may not preempt ideas, laws of nature or natural phenomena.

35 U.S.C. 112

The first paragraph of section 112 of title 35, United States Code, contains three separate and distinct requirements:

(A) adequate written description,

(B) enablement, and

(C) best mode.

Adequate Written Description

For the written description requirement, an applicant’s specification must reasonably convey to those skilled in the art that the applicant was in possession of the claimed invention as of the date of invention. The claimed invention subject matter need not be described literally, i.e., using the same terms, in order for the disclosure to satisfy the description requirement. Software aspects of inventions, for example, may be described functionally. See MPEP § 2163 for further guidance with respect to the evaluation of a patent application for compliance with the written description requirement.

Enabling Disclosure

An applicant’s specification must enable a person skilled in the art to make and use the claimed invention without undue experimentation. The fact that experimentation is complex, however, will not make it undue if a person of skill in the art typically engages in such complex experimentation.

See MPEP § 2164 et seq. for detailed guidance with regard to the enablement requirement of 35 U.S.C. 112(a).

Best Mode

Determining compliance with the best mode requirement requires a two-prong inquiry:

(1) at the time the application was filed, did the inventor possess a best mode for practicing the invention; and

(2) if the inventor did possess a best mode, does the written description disclose the best mode such that a person skilled in the art could practice it.

See MPEP § 2165 et seq. for additional guidance. Deficiencies related to disclosure of the best mode for carrying out the claimed invention are not usually encountered during examination of an application because evidence to support such a deficiency is seldom in the record.

35 U.S.C 112(b)

Formerly the second paragraph of 35 U.S.C. 112,  35 U.S.C. 112(b) contains two separate and distinct requirements: (A) that the claim(s) set forth the subject matter applicants regard as the invention, and (B) that the claim(s) particularly point out and distinctly claim the invention.

Novelty and Nonobviousness

Reviewing a claimed invention for compliance with 35 U.S.C. 102 and 103 begins with a comparison of the claimed subject matter to what is known in the prior art. If no differences are found between the claimed invention and the prior art, then the claimed invention lacks novelty and is to be rejected by USPTO personnel under 35 U.S.C. 102. Once differences are identified between the claimed invention and the prior art, those differences must be assessed and resolved in light of the knowledge possessed by a person of ordinary skill in the art. Against this backdrop, one must determine whether the invention would have been obvious at the time the invention was made. If not, the claimed invention satisfies 35 U.S.C. 103.


Section 102 of title 35, United States Code, provides:

A person shall be entitled to a patent unless –
(a) the invention was known or used by others in this country, or patented or described in a printed publication in this or a foreign country, before the invention thereof by the applicant for a patent, or
(b) the invention was patented or described in a printed publication in this or a foreign country or in public use or on sale in this country, more than one year prior to the date of application for patent in the United States, or
(c) he has abandoned the invention, or
(d) the invention was first patented or caused to be patented, or was the subject of an inventor’s certificate, by the applicant or his legal representatives or assigns in a foreign country prior to the date of the application for patent in this country on an application for patent or inventor”s certificate filed more than twelve months before the filing of the application in the United States, or
(e) the invention was described in – (1) an application for patent, published under section 122(b), by another filed in the United States before the invention by the applicant for patent or (2) a patent granted on an application for patent by another filed in the United States before the invention by the applicant for patent, except that an international application filed under the treaty defined in section 351(a) shall have the effects for the purposes of this subsection of an application filed in the United States only if the international application designated the United States and was published under Article 21(2) of such treaty in the English language; or
(f) he did not himself invent the subject matter sought to be patented, or
(g)(1) during the course of an interference conducted under section 135 or section 291, another inventor involved therein establishes, to the extent permitted in section 104, that before such person’s invention thereof the invention was made by such other inventor and not abandoned, suppressed, or concealed, or (2) before such person’s invention thereof, the invention was made in this country by another inventor who had not abandoned, suppressed, or concealed it. In determining priority of invention under this subsection, there shall be considered not only the respective dates of conception and reduction to practice of the invention, but also the reasonable diligence of one who was first to conceive and last to reduce to practice, from a time prior to conception by the other.

To anticipate a claim, a reference must teach every element of the claim. The courts have found, “A claim is anticipated only if each and every element as set forth in the claim is found, either expressly or inherently described, in a single prior art reference.” “When a claim covers several structures or compositions, either generically or as alternatives, the claim is deemed anticipated if any of the structures or compositions within the scope of the claim is known in the prior art.”  “The identical invention must be shown in as complete detail as is contained in the … claim.” The elements must be arranged as required by the claim, but this is not an ipsissimis verbistest, i.e., identity of terminology is not required.

Note that, in some circumstances, it is permissible to use multiple references in a 35 U.S.C. 102 rejection. See MPEP § 2131.01 and § 2131.02 for more detail.


Section 103(a) of title 35, United States Code, provides:

(a) A patent may not be obtained though the invention is not identically disclosed or described as set forth in section 102 of this title, if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art to which said subject matter pertains. Patentability shall not be negatived by the manner in which the invention was made.

The Supreme Court has particularly emphasized “the need for caution in granting a patent based on the combination of elements found in the prior art,” and discussed circumstances in which a patent might be determined to be obvious. Importantly, the Supreme Court reaffirmed principles based on its precedent that “[t]he combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results.” The Supreme court has also Court concluded that when a patent simply arranges old elements with each performing the same function it had been known to perform and yields no more than one would expect from such an arrangement, the combination is obvious.” The principles underlining these decisions are instructive when the question is whether a patent application claiming the combination of elements of prior art would have been obvious.

When a work is available in one field of endeavor, design incentives and other market forces can prompt variations of it, either in the same field or a different one. If a person of ordinary skill can implement a predictable variation, § 103 likely bars its patentability. For the same reason, if a technique has been used to improve one device, and a person of ordinary skill in the art would recognize that it would improve similar devices in the same way, using the technique is obvious unless its actual application is beyond his or her skill. When considering obviousness of a combination of known elements, the operative question is thus “whether the improvement is more than the predictable use of prior art elements according to their established functions.”

Once the examiner has considered the statutory requirements, do I get my patent?

In most cases, an examiner will determine that a patent application is deficient in at least one of the statutory requirements. After the application has been read, the claimed invention understood, and a prior art search made, the examiner will review and analyze the patent application in conjunction with the state of the prior art to determine whether the claims define a useful, novel, nonobvious, and enabled invention that has been clearly described in the specification. The goal of examination is to clearly articulate any rejection early in the prosecution process so that the applicant has the opportunity to provide evidence of patentability and otherwise reply completely at the earliest opportunity.

A first office action will typically reject at least part of the claims as being unpatentable. Don’t worry, this is normal. The applicant will then reply with arguments as to why the invention should be afforded patent protection. The examiner then reviews all the evidence, including arguments and evidence responsive to any rejection, before issuing the next Office action.

After reply by applicant or patent owner to a non-final action, the application will be reconsidered and again examined. The applicant will be notified if claims are rejected, objections or requirements made, or decisions favorable to patentability are made, in the same manner as after the first examination. The applicant may reply to such Office action with or without amendment, unless such Office action indicates that it is made final. If an application is finally rejected, the applicant may appeal, request continued examination, or abandon the application. If the final Office action allows the patent, the applicant must take care of some final procedural steps prior to an the actual issuance of the U.S. Patent.

How long does this all take?

This process usually takes years to complete. The lengthy pendency is partially due to the substantial backlog. The USPTO website includes a patent dashboard that summarizes the current statistics for time a patent application may pend before being finally disposed.

Do I need an patent attorney to help me with patent prosecution?

Patent prosecution is very complex. Patent attorneys dedicate their lives to learning the information presented above. Most inventors do not understand the law behind patentability, which may lead a critical misstep that may result in a rejected or unenforceable patent. If you need assistance or advice relating to the prosecution of your patent application, consider contacting a registered patent attorney such as Scott Nyman at or 312.487.2532.