Patent Invalidity Defenses

Test: Alice/Mayo two-step test

Claims directed to abstract ideas, laws of nature, or natural phenomena are patent-ineligible unless they contain an 'inventive concept' that transforms the ineligible concept into something more. Alice Corp. v. CLS Bank (2014) for software; Mayo Collaborative Services v. Prometheus (2012) for method-of-treatment. Frequently used against software, business method, and diagnostic claims. Available in district court and PGR; NOT available in IPR.

Test: Single prior art reference discloses every claim element

A claim is anticipated if a single prior art reference — patent, publication, prior use, on-sale bar, or prior art otherwise available — discloses every element of the claim, either explicitly or inherently. The reference must disclose each element in the claim, arranged as in the claim. Missing even one element defeats anticipation. Post-AIA effective filing date triggers the prior art analysis.

Test: Graham v. John Deere four-factor analysis + KSR

A claim is invalid if the differences between it and the prior art would have been obvious to a POSITA at the time of invention. Graham factors: (1) scope/content of prior art; (2) differences between prior art and claims; (3) level of ordinary skill; (4) secondary considerations. KSR expanded the grounds for combining references. Secondary considerations (commercial success, long-felt need, failure of others, unexpected results) can rebut a prima facie case.

Test: Wands factors (enablement) / Ariad (written description) / Nautilus (indefiniteness)

Three sub-grounds: (1) Enablement — claims not fully enabled without undue experimentation (Wands factors); (2) Written description — inventor not shown to have possessed the claimed invention at filing (Ariad); (3) Indefiniteness — claims fail to inform POSITA with reasonable certainty of scope (Nautilus). All three available in district court and PGR. NOT available in IPR.

What is the burden of proof for patent invalidity?

The burden of proof for patent invalidity depends on the forum. In federal district court, a patent is presumed valid under 35 U.S.C. § 282, and invalidity must be proven by clear and convincing evidence — a high bar that requires the challenger to overcome the USPTO's expert presumption that the patent was properly granted. In PTAB proceedings (inter partes review and post-grant review), invalidity is established by preponderance of evidence — a lower standard that essentially means 'more likely than not.' This difference in burden is one reason PTAB has become the preferred forum for defendants: institution rates in IPR have historically been 60–70%, and cancellation rates for instituted claims have been 50–65%. In ex parte reexamination, the examiner applies the preponderance standard.

What is the difference between anticipation and obviousness?

Anticipation (§ 102) and obviousness (§ 103) are the two prior-art invalidity grounds. Anticipation: a single prior art reference discloses every element of the claim, either explicitly or inherently. If even one element is missing from the reference, anticipation fails — you need 100% coverage from a single source. Obviousness: even if no single reference discloses every claim element, the claim is invalid if a person of ordinary skill in the art (POSITA) would have been motivated to combine references in a way that arrives at the claimed invention — using the Graham v. John Deere four-factor framework and the flexible KSR International v. Teleflex (2007) rationales. Obviousness allows combining multiple references and can reach broader claim scope than anticipation. The key distinctions: anticipation requires a single reference and is binary; obviousness requires the Graham analysis, is based on combinations, and the patent owner can rebut with secondary considerations (commercial success, long-felt need, failure of others, unexpected results).

What is indefiniteness as a patent invalidity ground?

Indefiniteness is an invalidity ground under 35 U.S.C. § 112(b), which requires that patent claims 'particularly point out and distinctly claim the subject matter' the inventor regards as the invention. Nautilus, Inc. v. Biosig Instruments, Inc. (Supreme Court 2014) established the current standard: a claim is indefinite if it fails to inform a person of ordinary skill in the art, with reasonable certainty, of the scope of the invention — when read in light of the specification and prosecution history. Common indefiniteness situations: (1) 'about,' 'substantial,' 'approximately,' and similar relative terms — indefinite if no objective standard is provided in the specification; (2) Means-plus-function claims (§ 112(f)) where the corresponding structure is not identifiable in the specification; (3) Claims using multiple inconsistent antecedents; (4) Claims with numerical ranges that cannot be determined with precision. In district court, indefiniteness is decided by the court (not the jury) at Markman claim construction. In PTAB, § 112(b) grounds are available in PGR but not in IPR.

Should I challenge a patent in IPR or in district court?

The choice between IPR and district court invalidity requires strategic analysis. IPR advantages: lower burden (preponderance vs. clear and convincing); specialized PTAB judges with technical expertise; faster resolution (12 months after institution vs. 3–5 years for trial); lower cost ($200K–$600K vs. $3M–$10M+); co-pending IPR can stay district court litigation. IPR disadvantages: grounds limited to § 102 and § 103 prior art (no § 101 Alice challenges, no § 112 written description or enablement); strong estoppel at final written decision — any ground raised or reasonably could have been raised is foreclosed in district court; 1-year deadline from service of infringement complaint; if petition denied, defendant loses the IPR option but not the district court invalidity defense. PGR is available only for AIA patents within 9 months of grant — it allows all grounds including § 101 and § 112. Best practice: for a patent that has both prior art and § 101 issues, consider a coordinated strategy — PGR (if within 9 months of grant) for all grounds, or selective IPR for the strongest prior art grounds while preserving § 101 and § 112 for district court. Consult patent litigation counsel to model the estoppel consequences of each path.

Can a patent be invalid due to the on-sale bar or prior public use?

Yes — under 35 U.S.C. § 102(a)(1), a patent claim is invalid if the claimed invention was patented, described in a printed publication, in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention (post-AIA) or more than 1 year before the filing date (pre-AIA grace period). The on-sale bar applies when: (1) the claimed invention was the subject of a commercial sale or offer for sale; and (2) the invention was ready for patenting (either reduced to practice, or depicted in drawings or written descriptions sufficient for enablement). Helsinn Healthcare S.A. v. Teva Pharmaceuticals USA, Inc. (Supreme Court 2019): the AIA's 'on sale' language includes even confidential sales — a secret sale to a third party still triggers the bar. Public use invalidation: the claimed invention was used by someone other than the inventor, in public, without restriction. Pre-AIA: these events more than 1 year before the US filing date create a statutory bar. Post-AIA: the grace period protects only the inventor's own disclosures within 1 year of filing; third-party disclosures and sales do not have a grace period and create prior art immediately.