5.3 Best Mode Requirement & Current Post-AIA Status

5.3 Best Mode Requirement & Current Post-AIA Status

Under the statutory language of 35 U.S.C. § 112(a), the specification 'shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention.' The purpose of this requirement historically was to prevent an inventor from obtaining a patent monopoly while concealing from the public their preferred embodiment or superior method of practicing the invention.

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The Two-Prong Best Mode Test

Evaluating compliance with the best mode requirement requires a sequential two-prong analysis established by Federal Circuit case law (Chemcast Corp. v. Arco Industries Corp., 913 F.2d 923 (Fed. Cir. 1990)) and detailed in MPEP § 2165:

1. The Subjective Prong (Inventor State of Mind)

• Question: Did the inventor, at the time of filing the application, actually possess or contemplate a preferred mode of practicing the claimed invention?
• Nature: Entirely subjective. It focuses exclusively on what the inventor personally believed at the filing date.
• Timing: Evaluated as of the application filing date. If the inventor discovered a better mode after filing, there is no requirement to update the application.
• Result: If the inventor did not contemplate a best mode (believed all embodiments were equal), the analysis ends — there is no best mode violation.

2. The Objective Prong (Adequacy of Disclosure)

• Question: If the inventor contemplated a best mode, did the specification disclose sufficient information to enable a POSITA to practice that best mode?
• Nature: Objective. It asks whether the disclosure concealed the best mode or failed to enable POSITA to practice the inventor's preferred embodiment.
• Concealment Types: Express concealment (omitting critical parameters), passive concealment (burying the best mode in a mountain of inferior alternatives without indication), or failure to disclose essential proprietary trade secret settings.

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Post-AIA Statutory Change: 35 U.S.C. § 282(b)(3)(A)

The Leahy-Smith America Invents Act (AIA), enacted on September 16, 2011, fundamentally transformed how the best mode requirement is enforced in litigation and post-grant proceedings.

Congress enacted 35 U.S.C. § 282(b)(3)(A), which explicitly states:

'[T]he failure to disclose the best mode shall not constitute a basis on which any claim of a patent may be canceled or held invalid or otherwise unenforceable...'

Impact of AIA on Best Mode Enforcement

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Current Examination Standard at the USPTO (MPEP § 2165)

Despite the AIA litigation bar, the statutory text of 35 U.S.C. § 112(a) still includes the requirement to set forth the best mode. As a result, USPTO examination guidelines in MPEP § 2165 maintain that examiners must still apply the requirement during initial ex parte examination.

Practical Reality of USPTO Examination

In practice, rejections under § 112(a) for lack of best mode during examination are extremely rare. Why?

1. Lack of Evidence: Patent examiners examine applications based solely on the written record submitted. An examiner has no mechanism during initial examination to probe the subjective mind of the inventor to determine if they contemplated a preferred mode.
2. Presumption of Good Faith: Unless the applicant explicitly admits on the record that they concealed their preferred embodiment, the examiner must presume the applicant complied with the requirement.

When Might an Examiner Issue a Best Mode Rejection?

An examiner will issue a best mode rejection during examination only if:

• The applicant explicitly states in the specification or in a declaration under 37 CFR 1.132 that a specific un-disclosed trade secret or parameter is the preferred embodiment; or
• Evidence in a parent application or companion document explicitly shows the inventor concealed their best mode.

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Ethical & Inequitable Conduct Implications

Even though an infringer cannot invalidate an issued patent in court based on a best mode defense under 35 U.S.C. § 282(b)(3)(A), patent practitioners and inventors must remain compliant during drafting:

• Duty of Candor (37 CFR 1.56): Intentionally misleading the USPTO or making false statements regarding preferred embodiments during prosecution can constitute inequitable conduct, rendering the entire patent unenforceable.
• Foreign Filing Considerations: Many foreign patent offices (and international filing standards) scrutinize disclosure completeness. Omitting preferred operational parameters can severely damage international patent rights.