4.2 Combining Prior Art References & Motivation to Combine

4.2 Combining Prior Art References & Motivation to Combine

The Analogous Art Doctrine (MPEP § 2141.01(a))

Before a prior art reference can be combined with another reference under 35 U.S.C. § 103, it must qualify as "analogous art." The USPTO applies a strict two-prong test to determine whether a reference constitutes analogous art:

1. Prong 1: Field of Endeavor: Is the prior art reference from the same field of endeavor as the claimed invention, regardless of the specific problem addressed?
2. Prong 2: Reasonably Pertinent to the Problem: If the reference is not from the same field of endeavor, is it nevertheless reasonably pertinent to the particular problem with which the inventor was involved?

A reference is reasonably pertinent if it is one that a person of ordinary skill in the art (POSITA) would naturally look to for a solution to the specific problem facing the inventor. For example, in In re Bigio, 381 F.3d 1320 (Fed. Cir. 2004), a tooth-brushing structure was evaluated against prior art hairbrushes because both involved bristles mounted on hand-held substrates, placing them within a shared broader field of endeavor. Conversely, in In re Klein, 647 F.3d 1343 (Fed. Cir. 2011), references dealing with fixed-ratio liquid dividers were held not analogous to a claimed standing water divider because the prior art references failed to address the specific problem of dividing fluid from a standing, unpressurized source.

Analyzing the Field of Endeavor vs. Problem Solved

When evaluating Prong 1, examiners and practitioners look to the structure, function, and explicit disclosures of the prior art reference rather than its labeled title alone. If the reference originates from the same technical industry or discipline (e.g., semiconductor fabrication), it automatically satisfies Prong 1 even if it solves a different sub-problem.

When evaluating Prong 2, the inquiry focuses on the specific problem disclosed in the patent application. If an inventor is attempting to reduce mechanical friction in a high-speed hinge, references from aerospace engineering, automotive suspension, or office furniture hinges may all qualify under Prong 2 if they address friction reduction mechanisms, even though they belong to distinct commercial fields.

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Motivation to Combine & Reasonable Expectation of Success

To establish a valid obviousness rejection when combining multiple prior art references, an Examiner must demonstrate both:

• A clear motivation to combine or modify the references (supported by one of the MPEP § 2143 rational underpinnings).
• A reasonable expectation of success in achieving the claimed combination (MPEP § 2143.02).

Post-KSR, motivation need not be explicitly stated within the four corners of the prior art references; it can arise from market forces, design trends, scientific principles, or the background knowledge of a POSITA. However, Examiner speculation is strictly improper. The Examiner must articulate an explicit, reasoned explanation grounded in factual evidence. Furthermore, a reasonable expectation of success does not require absolute certainty or guaranteed results, but it demands more than a mere speculative hope. If unpredictable chemical reactions or complex biological interactions prevent a POSITA from expecting success, the combination is nonobvious.

Articulating a Sound Motivation under MPEP § 2143

Under MPEP § 2143, the Examiner must articulate a clear rationale explaining why a POSITA would have been prompted to combine the primary reference with the secondary reference. Standard rationales include:

• Design Incentives: Replacing a heavy metal casing with a lightweight composite polymer to improve portability or fuel efficiency.
• Market Demand: Adapting a desktop software user interface for touch-screen mobile devices based on consumer preference.
• Predictable Combination: Combining a known heating element with a known fluid pump where each component performs its conventional, expected function without unexpected synergistic interaction.

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The Teaching Away Doctrine (MPEP § 2145)

A prior art reference cannot support an obviousness rejection if it "teaches away" from the claimed invention. Under MPEP § 2145 and Federal Circuit precedent (In re Gurley):

A reference teaches away if a person of ordinary skill in the art, upon reading the reference, would be discouraged from following the path set out in the reference, or led in a direction contrary to the path taken by the applicant.

Distinguishing Teaching Away from Mere Preference

Examiners frequently cite prior art that discloses multiple embodiments or alternatives. It is a fundamental rule of patent law that a reference's disclosure of a preferred embodiment does not constitute a teaching away from its non-preferred embodiments. To establish a genuine teaching away, the reference must contain explicit statements disparaging the proposed modification (e.g., "adding water to this solvent mixture causes immediate decomposition") or demonstrating technical failure.

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Secondary Considerations & Objective Evidence (MPEP § 716)

Secondary considerations (objective evidence of nonobviousness) must always be considered by Examiners when presented, as established by Graham v. John Deere. Objective evidence can overcome even a strong prima facie case of obviousness.

The five primary categories of objective evidence under MPEP § 716 are:

1. Commercial Success: Widespread market acceptance of the claimed product. To carry evidentiary weight, the applicant MUST establish a nexus—a direct causal relationship between the claimed novel features and the commercial success (rather than advertising, brand recognition, or market positioning).
2. Long-Felt But Unsolved Need: Evidence that the industry faced a persistent problem for an extended period, which others attempted but failed to solve until the applicant's invention.
3. Failure of Others: Documented unsuccessful efforts by competitors or research institutions to achieve the claimed result.
4. Copying by Competitors: Competitors explicitly copying the applicant's proprietary design or product rather than relying on prior art.
5. Unexpected Results: Achieving properties or capabilities superior in kind or degree compared to what POSITA would have predicted (In re Soni).

Establishing the Legal Nexus Requirement

Under MPEP § 716.01(b), objective evidence of nonobviousness is entitled to no weight unless the applicant proves a legal nexus. A nexus is a demonstrated causal connection between the submitted evidence and the claimed invention.

For instance, if an applicant submits sales figures demonstrating $50 million in revenue, but the commercial product includes unclaimed promotional features or benefits from an enormous marketing budget, the Examiner will discount the evidence for lack of nexus. To establish nexus, the applicant must present a declaration under 37 C.F.R. § 1.132 demonstrating that consumers purchased the product specifically because of the technical features recited in the patent claims.