Federal Circuit Clarifies Secret Prior Art May Be Used in IPR Challenges

On January 14, 2025, the Federal Circuit in Lynk Labs Inc. v. Samsung Electronics Co. Ltd. clarified that inter partes review challenges may be “based upon published patent applications, and such published patent applications can be deemed prior art in IPRs as of their filing date.”

Both sides agreed that the reference at issue, Martin—a published patent application—was a “printed publication” within the scope of Section 311(b) of the Patent Act but disagreed about Martin’s treatment as prior art to the challenged patent. Applying the law prior to the effective date of the Leahy-Smith America Invents Act (pre-AIA law), the court held that “§ 102(e)(1) treats this type of printed publication as prior art as of a time before it became publicly accessible—i.e., as of its filing date.”[1]

Section 311(b) of the Patent Act permits inter partes review (IPR) unpatentability challenges “on the basis of prior art consisting of . . . printed publications.”[2] Although the patent owner agreed that Martin was a printed publication, it argued that Martin was not prior art because it was published after the priority date of the challenged patent.[3] The patent owner, however, relied on cases analyzing prior art status under Section 102(a) and (b) that contemplate “books, articles, [and] the like,” [4] which “stand for the proposition that, to be a prior art printed publication . . . the reference at issue must have been publicly accessible before the” priority date. [5]  

The issue with this approach, however, according to the Federal Circuit, was that it ignored Section 102(e)(1), which is “a special rule for published patent applications.”[6] In the court’s historical analysis, it explained that Lynk Labs’ cited cases predated Congress’s providing for the publishing of patent applications and enactment of the special prior-art rule that Congress prescribed in Section 102(e)(1), both of which were provided for in the American Inventors Protection Act in 1999.[7] Accordingly, under Section 102(e)(1)’s special rule, “even if a patent application was published after a claimed invention, it may serve as prior art to the invention if the application was filed before the invention.”[8] Accordingly, Martin was a prior art printed publication within the scope of Section 311(b) because it was filed before the challenged patent’s priority date.

Even though Lynk Labs applied pre-AIA law, IPRs applying post-AIA law are likely to apply the Lynk Labs holding, given similar statutory language relating to published patent applications. Pre-AIA Section 102(e)(1) states that “A person shall be entitled to a patent unless . . . (e) the invention was described in—(1) an application for patent, published under [35 USC §] 122(b), by another filed in the United States before the invention by the applicant for patent . . . .”[9]

Likewise, AIA Section 102(a)(2) states that “A person shall be entitled to a patent unless . . . (2) the claimed invention was described . . . in an application for patent published or deemed published under section 122(b), in which the . . . application . . . names another inventor and was effectively filed before the effective filing date of the claimed invention.”[10] Indeed, the Federal Circuit recently alluded to this similar treatment in Sanho Corp. v. Kaijet Technology International Ltd., which discussed the exception to prior art treatment under Section 102(b)(2)(B).[11] The Sanho decision, on appeal from an IPR and applying the AIA, states, that “[P]rior art includes other patent applications effectively filed . . . before the effective filing date of the patent at issue.”[12]

For stakeholders utilizing IPR proceedings, this precedential opinion serves to resolve an open question as to the scope of prior art available for IPR proceedings. For petitioners and patent owners alike, this decision now ensures uniformity between district court and IPR in terms of available prior art. Further, for patent-portfolio managers and patent prosecutors, this opinion serves as a reminder that hidden or secret prior art remains a concern. Thus, patent applicants should not expect that a prior art search conducted before filing a patent application will reveal every reference that can be cited as prior art. In certain circumstances, it may be wise for a patent owner to conduct a new prior art search prior to filing continuation and divisional applications, as well as prior to enforcement, to determine if any new prior art has appeared since the original filing.