35 USC 103: Obviousness, Prior Art, and Patent Rejections

Under 35 U.S.C. 103, obviousness bars a patent when the differences between the claimed invention and the prior art would have been obvious, as a whole, to a person having ordinary skill in the relevant field before the application’s effective filing date.¹ An invention can be new under Section 102 and still fail here. Novelty asks whether the invention exists in the prior art; obviousness asks whether a competent worker in the field would have arrived at it anyway by combining, tweaking, or applying what was already known.

What Section 103 Requires

The statute itself is short. It denies a patent if the claimed invention and the prior art differ only in ways that would have been obvious, as a whole, to a person of ordinary skill in the art as of the effective filing date. A second sentence adds that the manner in which the invention was made does not matter. A lucky accident and a decade of deliberate research get the same treatment.¹

A few phrases carry most of the weight. “As a whole” means an examiner cannot pick the claim apart element by element and dismiss each piece separately; the invention is judged as a complete package. “Before the effective filing date” locks the analysis to a fixed moment, which prevents the applicant’s own disclosure from being turned against them. And the “person having ordinary skill in the art” is a hypothetical professional who serves as the yardstick for what counts as obvious. Each of those phrases has generated decades of case law.

The Prior Art That Feeds the Analysis

Obviousness analysis rides on what qualifies as prior art, and Section 102 defines that broadly. Prior art includes anything patented, described in a printed publication, in public use, on sale, or otherwise available to the public before the effective filing date, along with patents and published applications filed by others before that date.²

The prior art does not have to come from the same field. If a technique from automotive engineering solves the same problem as an applicant’s medical device claim, that reference is fair game, provided a skilled person in the applicant’s field would have known about it or had reason to look for it.

Who the Person of Ordinary Skill Is

The whole obviousness question turns on a fictional character. The person having ordinary skill in the art is not a leading researcher or a genius. It is a hypothetical professional with typical education and work experience for that field, who is presumed aware of all publicly available information in the relevant area. Examiners and courts build this figure from scratch for every case.

The USPTO’s guidelines identify several factors that shape the baseline:

The kinds of problems that regularly come up in the field
How others have previously solved those problems
How quickly the technology is evolving
The sophistication of the underlying science or engineering
The typical formal education of workers in the field

Not every factor carries equal weight in every case, and one sometimes dominates.³ A person of ordinary skill in semiconductor fabrication has a very different knowledge base than one in kitchen utensil design, and the standard scales accordingly.

The Supreme Court in KSR v. Teleflex emphasized that this hypothetical person is not a robot. They have “ordinary creativity” and can draw on common sense, not only on the specific teachings found in published documents.⁴ That distinction matters because it means an examiner does not need a written instruction telling someone to try a particular combination. The skilled person can connect dots on their own.

The Graham Framework Examiners and Courts Use

The Supreme Court’s 1966 decision in Graham v. John Deere Co. established the analytical framework still in use today. Three factual inquiries must be completed before any conclusion about obviousness:

The scope and content of the prior art
The differences between the prior art and the claims at issue
The level of ordinary skill in the art

These inquiries are the required foundation for every obviousness determination, in the examiner’s office and in federal court alike.⁵

Secondary Considerations

Graham also recognized a fourth element: real-world evidence that can illuminate whether an invention was truly obvious. The Court specifically identified commercial success, long-felt but unsolved needs, and the failure of others.⁵ These indicators check what could otherwise become a purely theoretical exercise. If several companies tried and failed to solve a problem for years, and then the applicant cracked it, that history is powerful evidence the solution was not obvious.

Other secondary considerations that come up in practice include unexpected results, industry skepticism that the approach would work, and copying by competitors. They tend to matter most when the technical gap between the old and new designs looks small on paper but proved significant in the field.

The Nexus Requirement

Secondary considerations only help when the applicant can tie them to the actual claimed invention. That link is called nexus, and without it, evidence of commercial success or industry praise carries no weight. A product might sell millions of units because of marketing or brand loyalty rather than the patented feature, and the applicant bears the burden of showing the connection.⁶

Nexus is presumed when the product embodying the evidence is coextensive with the claimed features, meaning the product essentially is the claimed invention without significant unclaimed extras driving the success. Where no presumption applies, the applicant can still prove nexus by showing the success flows directly from the unique characteristics of what is claimed. If it flows from something already in the prior art, nexus fails.⁶

Combining References After KSR

A novelty rejection under Section 102 typically requires a single reference that discloses every element of the claim. Obviousness rejections work differently. An examiner can stitch together two, three, or more references, pulling one feature from a patent, another from a technical manual, and a third from a product on the market, to argue that the combination was predictable. Most Section 103 rejections come from this patchwork approach, and it is where the hardest arguments happen.

Before KSR International Co. v. Teleflex Inc. in 2007, the Federal Circuit applied a relatively rigid “teaching, suggestion, or motivation” test. An examiner needed to point to something specific in the prior art, the nature of the problem, or the knowledge of a skilled person that would have prompted the combination. KSR rejected that rigidity and replaced it with a more flexible analysis.⁴

The Court identified several rationales that can support an obviousness finding:

Combining familiar elements according to known methods when the result is what you would expect
Simple substitution of one known element for another to achieve predictable results
“Obvious to try” when a problem has a limited number of identified, predictable solutions
Applying a known technique to a similar device in the same way, unless the application requires unusual skill
Market pressure and design needs providing motivation to combine existing ideas even when no publication suggested it

The practical effect is that examiners have more room to combine references, because they no longer need a paper trail explicitly suggesting the combination.⁴ Applicants, in turn, face a steeper climb when arguing that references “wouldn’t have been combined” if the combination produces no surprises.

Responding to a Section 103 Rejection

An obviousness rejection during prosecution is common and rarely fatal. Applicants have several tools, and the strongest responses usually blend more than one.

Amending the Claims

The most direct response is narrowing the claims to distinguish the invention from the cited prior art. Adding a specific limitation that none of the references disclose can eliminate the basis for the rejection. The risk is over-narrowing: claims too narrow to reach competitors’ designs may not be worth much commercially. Good drafting finds the narrowest amendment that clears the rejection while preserving meaningful scope.

Challenging the Combination

Examiners have broad latitude after KSR, but they still must give a clear reason why a skilled person would have made the specific combination. The MPEP requires that the analysis “be made explicit” and include a “clear articulation of the reason(s) why the claimed invention would have been obvious.”⁷ A conclusory rationale, or one that leans on “common sense” without tying it to the specific references and claims, is attackable.

Teaching Away

If one of the cited references actually discourages the modification the examiner proposes, that is strong rebuttal material. The inference of non-obviousness gets stronger when the prior art undermines the very rationale used to combine the references.⁸ If a reference explicitly warns against increasing a particular dimension because it causes failure, and the applicant’s claim requires that very increase, the combination argument weakens.

Unexpected Results

Showing that the claimed invention produces results nobody would have predicted can overcome a rejection even when the structural differences look minor. Chemical and pharmaceutical cases turn on this often, because small molecular changes can produce dramatically different biological activity. The results must be genuinely unexpected, not marginally better than what came before.⁸

Declarations Under 37 CFR 1.132

When argument alone is not enough, applicants can submit sworn declarations providing factual evidence. Declarations may include data on unexpected results, evidence of commercial success, testimony about long-felt need, or expert opinion on the level of skill. The declarant affirms that statements based on personal knowledge are true and that statements based on information and belief are believed to be true, and the examiner weighs whether the evidence is enough to overcome the specific rejection.⁶

The Hindsight Problem

Hindsight is the quiet enemy of every obviousness analysis. Once you see how an invention works, the solution can look straightforward. Graham acknowledged the problem, and much of the analytical framework exists to impose discipline on what would otherwise be a subjective, backward-looking judgment.

The MPEP addresses this directly. Reconstructing the invention from prior art is permissible only when the analysis relies on knowledge that was within the ordinary skill level at the time of filing. The examiner cannot use information learned from the applicant’s own disclosure as the roadmap for the rejection.⁹ Reading the application, seeing how the pieces fit, and then hunting for references that match each piece is exactly what the rule prohibits.

Secondary considerations do most of the judicial work against hindsight. When an applicant can show competitors failed at the same problem, or that experts doubted the approach, that evidence counters the pull to treat the invention as simple after the fact. Skipping secondary considerations in prosecution leaves one of the strongest available tools on the table.

A Related Doctrine: Obviousness-Type Double Patenting

The Section 103 concept of obviousness also appears in a different setting worth flagging so it doesn’t cause confusion later. Obviousness-type double patenting is a judge-made doctrine, not a statutory requirement, and it prevents a patent owner from effectively extending a monopoly by obtaining a second patent whose claims are not patentably distinct from those of an earlier one. If the claims of a later application are an obvious variation of the claims in an earlier patent owned by the same applicant, the later application faces rejection.

The typical fix is a terminal disclaimer, which shortens the later patent’s term so it expires on the same date as the earlier one and includes a provision making the later patent unenforceable if the two are no longer commonly owned.¹⁰ Terminal disclaimers are only available while the reference patent is still active, so applicants with related applications should address potential double patenting early rather than waiting until the option is gone.

1
Office of the Law Revision Counsel. 35 USC 103 – Conditions for Patentability; Non-Obvious Subject Matter
2
Office of the Law Revision Counsel. 35 USC 102 – Conditions for Patentability; Novelty
3
United States Patent and Trademark Office. Manual of Patent Examining Procedure Section 2141
4
Justia U.S. Supreme Court Center. KSR Int’l Co. v. Teleflex Inc.
5
Justia U.S. Supreme Court Center. Graham v. John Deere Co.
6
United States Patent and Trademark Office. Affidavits or Declarations Under 37 CFR 1.132 and Other Evidence Traversing Rejections
7
United States Patent and Trademark Office. Manual of Patent Examining Procedure Section 2143 – Examples of Basic Requirements of a Prima Facie Case of Obviousness
8
United States Patent and Trademark Office. Manual of Patent Examining Procedure Section 2144 – Supporting a Rejection Under 35 USC 103
9
United States Patent and Trademark Office. Manual of Patent Examining Procedure Section 2145 – Consideration of Applicant’s Rebuttal Arguments and Evidence
10
eCFR. 37 CFR 1.321 – Statutory Disclaimers, Including Terminal Disclaimers