Best Mode Requirement

The best mode requirement under 35 U.S.C. § 112(a) obligates inventors to disclose the best way they know to practice the claimed invention at the time of filing: STATUTORY TEXT: § 112(a): 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 pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention'; TWO-PRONG TEST (Chemcast Corp. v. Arco Indus., Fed. Cir. 1991): PRONG 1 (SUBJECTIVE): did the inventor subjectively contemplate a best mode at the time the application was filed? This is a subjective inquiry — what did THIS inventor actually believe was the best way?; PRONG 2 (OBJECTIVE): if the inventor had a best mode, was it adequately disclosed to enable one skilled in the art to practice it without undue experimentation?; WHAT CONSTITUTES A BEST MODE: the best mode is the preferred embodiment — the specific combination of materials, processes, parameters, or configurations the inventor believed was optimal; it may include specific commercial products the inventor used (e.g., a specific commercial grade of resin, a specific supplier), specific process conditions (temperature, pressure, timing), or specific implementation details the inventor discovered were superior; KEY POINT: the best mode requires more than mere enablement; the inventor must disclose the best way, not just any way.

The America Invents Act (AIA, effective September 16, 2012) made a significant change to the best mode requirement: PRE-AIA LAW: under pre-AIA law, failure to disclose the best mode was grounds for invalidity and unenforceability of a patent; a patent could be held invalid in district court infringement litigation if the defendant proved the inventor concealed or failed to disclose the best mode; this was a frequently asserted invalidity defense; AIA CHANGE (35 U.S.C. § 282(b)(3)): the AIA eliminated best mode as a basis for invalidity or unenforceability in CIVIL ACTIONS for patent infringement; § 282(b)(3)(A) explicitly states that best mode failure shall not be the basis on which a claim is held invalid or the patent is held unenforceable in a civil action; WHAT REMAINS: best mode still matters: (1) PROSECUTION: an examiner can reject claims under § 112(a) for failure to disclose the best mode during examination; applicants must still include the best mode in the specification; (2) POST-GRANT REVIEW (PGR): PGR proceedings under the AIA can challenge patents for best mode failure (for patents with effective filing dates on or after March 16, 2013); (3) INTER PARTES REVIEW (IPR): best mode cannot be raised in IPR (IPR is limited to § 102 and § 103 grounds); PRACTICAL EFFECT: the AIA change dramatically reduced the importance of best mode in litigation; defendants can no longer invalidate an otherwise-valid patent solely because the inventor failed to disclose their preferred embodiment; DISCLOSURE PRACTICE: patent drafters still include best mode disclosures in specifications to avoid prosecution rejections and PGR challenges.

A best mode violation occurs when an inventor knowingly conceals the preferred way to practice the invention: EXAMPLES OF BEST MODE VIOLATIONS: (1) SPECIFIC PREFERRED MATERIALS: inventor uses a specific commercially available adhesive that provides superior results; specification describes the generic category of adhesives without disclosing the specific product; if the inventor believed the specific product was the best mode, omitting it may be a violation; (2) OPTIMAL PROCESS CONDITIONS: inventor determines through experimentation that a specific temperature and pressure combination produces the best results; specification describes a range but omits the optimal point within that range; (3) PREFERRED EQUIPMENT VENDOR: inventor uses equipment from a specific vendor whose performance is superior; specification doesn't identify the vendor; (4) PROPRIETARY FORMULAS: inventor develops a proprietary formulation that achieves superior results but discloses only a generic description; WHAT DOES NOT VIOLATE BEST MODE: (1) UNKNOWING OMISSION: the best mode requires the INVENTOR to subjectively contemplate the best mode; if the inventor didn't realize they had a preference, there is no violation; (2) FUTURE IMPROVEMENTS: the best mode is determined as of the FILING DATE; improvements discovered after filing need not be disclosed in the original application; (3) ROUTINE EXPERIMENTATION: an inventor is not required to disclose every variable that a skilled artisan could optimize through routine experimentation; (4) NOT IN THE CLAIMS: technically, best mode applies to the 'invention' — which is defined by the claims; concealment of features outside the claimed scope may not be a best mode violation.

Best mode is one of three related but distinct requirements in § 112(a) — written description, enablement, and best mode: WRITTEN DESCRIPTION: the specification must describe the invention in sufficient detail to show the inventor actually possessed the claimed invention at the time of filing; asks: does the specification show the inventor had the complete invention?; ENABLEMENT: the specification must teach a person of ordinary skill in the art how to make and use the full scope of the claimed invention without undue experimentation; asks: can a skilled artisan make and use the invention from the disclosure?; BEST MODE: the specification must disclose the inventor's preferred way of practicing the invention; asks: did the inventor disclose the BEST way they knew, not just any way?; OVERLAP: the three requirements can overlap: a specification that enables the invention but conceals the best mode satisfies enablement but not best mode; a specification that discloses the best mode may still fail enablement if it doesn't teach a skilled artisan how to practice the full claim scope; BEST MODE AND ENABLEMENT — KEY DIFFERENCE: enablement focuses on what a skilled artisan needs to practice the invention; best mode focuses on what the inventor believed was the optimal way; an inventor can satisfy enablement without satisfying best mode (if they disclose enough to enable but conceal the optimal implementation); Amgen v. Sanofi (S.Ct. 2023): reinforced the full-scope enablement requirement; Amgen's genus antibody claims required enablement of the full scope — related to best mode analysis in that broad claims require broad disclosure.

Best practice guidance for satisfying the best mode requirement during prosecution and in anticipation of post-grant challenges: INTERVIEW THE INVENTORS: the most important step; specifically ask inventors: 'What is the best way you currently know to practice the invention?'; 'Have you tested different approaches and found one to be superior?'; 'Are there specific materials, suppliers, conditions, or processes you prefer?'; DISCLOSE SPECIFIC PREFERRED EMBODIMENTS: include specific preferred examples in the specification with actual conditions, materials, and parameters used by the inventors; don't abstract away specific information that the inventor knows to be optimal; disclose preferred suppliers, preferred commercial grades, preferred specific conditions; AVOID 'GENERIC DESCRIPTION OF PREFERRED': describing only 'preferred ranges' or 'preferred materials categories' without the specific preference may fail best mode if the inventor actually has a specific preference within that range; TIMING: best mode is assessed as of the FILING DATE; at the time of filing, include all known best modes; later developments are not required to be added (though they may be relevant to continuation applications); UPDATING IN CONTINUATIONS: if an inventor later develops an improved best mode, the continuation or CIP application should disclose the new best mode; INTERNATIONAL APPLICATIONS: foreign patent offices (EPO, JPO) have different disclosure requirements; under the EPC, there is no best mode requirement, but the EP specification must still enable the full claim scope; under PCT, the best mode requirement applies based on the applicable national law.