Section 103 does not, by its terms, define the “art to which [the] subject matter [sought to be patented] pertains,” but longstanding precedent couches this question of fact in terms of “whether the art is analogous or not.” See In re Clay, 966 F.2d 656, 658 (Fed. Cir. 1992); Application of Wood, 599 F.2d 1032, 1036 (C.C.P.A. 1979). There are two distinct, yet equally effective, criteria for determining whether a reference is analogous art.
“Two separate tests define the scope of analogous prior art: (1)whether the art is from the same endeavor, regardless of the problem addressed and, (2) if the reference is not within the field of the inventor’s endeavor, whether the reference still is reasonably pertinent to the particular problem with which the inventor is involved.”
In re Bigio, 381 F.3d 1320, 1325 (Fed. Cir. 2004); In re Oetiker, 877 F.2d 1143, 1447 (Fed. Cir. 1992). Whether or not a reference is analogous to subject matter sought to be patented is a threshold question as to whether the reference may be considered in an obviousness combination at all. See, JDS Uniphase Corporation v. Fiber, LLC, IPR2013-00336 at 34 (P.T.A.B. December 5, 2014) (after finding references analogous “[w]e still address, however, whether one of ordinary skill in the art would have had reason to combine the elements disclosed [in separate prior art references]”).
The PTAB regularly considers Patent Owner arguments that asserted grounds rely on non‑analogous art that is both outside the patent’s field of endeavor and fails to address the particular problem with which the inventor is involved. But a search of PTAB decisions illustrates that this argument rarely succeeds. Within the last quarter, for example, the PTAB issued sixteen decisions (under 37 C.F.R. §§ 42.73, 42.108) that consider the question of analogous art, and in each case the PTAB has sided with Petitioner finding that the asserted art was analogous art. These decisions predominantly are resolved under the first prong as in the same field of endeavor, but four of these decision considered the second prong asking whether an asserted reference is analogous art as “reasonably pertinent to the particular problem with which the inventor is involved.” In each case the PTAB found the asserted art to be pertinent to the problem faced by the inventor in spite of the Patent Owner’s arguments to the contrary. Many times, the result that a reference is analogous art is responsive to rote arguments reciting analogous art standards in the form of conclusory assertions, but a handful of decisions shed some light on the reasonably pertinent prong analysis.
In order for a reference to be reasonably pertinent, it must “logically  have commended itself to an inventor’s attention in considering his problem.” In re Icon Health and Fitness, Inc., 496 F.3d 1374, 1379-80 (Fed. Cir. 2007). This requires “consider[ing] ‘the reality of the circumstances’… in other words, common sense.” In re Oetiker, 977 F.2d at 1447 (quoting In re Wood, 599 F.2d 1032, 1036 (CCPA 1979)). The PTAB will find a reference analogous art if it “is at least reasonably pertinent to one of the problems confronting the inventors of the [challenged] patent.” Baker Hughes, a GE Company, LLC v. LiquidPower Specialty Products Inc., IPR2016-00734, Paper 85, at 50-52 (P.T.A.B. November 1, 2017) (emphasis added); see also Fisher & Paykel Healthcare Limited1 v. ResMed Ltd., IPR2017-00340, 2017 WL 2188526 at *11 (P.T.A.B. 2017). The Fisher & Paykel decision is illustrative of when art may be pertinent. See, 2017 WL 2188526 at *11-12; see also IPR2016-00734, Paper 85, at 51-52.
In Fisher & Paykel, for example, the PTAB rejected an argument that for a reference to be reasonably pertinent to the problem confronting the inventor of a challenged patent, the reference must address “each and every problem” addressed by the inventors of the patent. 2017 WL 2188526 at *11 (emphasis in original). Based on this argument, Patent Owner recited “several problems” addressed by the patent while arguing the asserted reference failed to address each of them, and so could not be analogous art. Id. But, the PTAB held it “[does] not read the law to be that restrictive,” finding the asserted reference was analogous art because it was reasonably pertinent to “an entire problem addressed by the [challenged patent].” Id. (emphasis in original). In other words, the Fisher PTAB concluded that a prior art reference is pertinent if it addresses at least one entire problem of one or more problems addressed by the patent. See, id.
In summary, when a reference is not in the same field of endeavor, a Petitioner can still attempt to rely on the reference being reasonably pertinent to just one problem addressed by the patent and succeed. And, practitioners should generally avoid making legally technical arguments that would limit the scope of the prior art without justification or that would defy common sense.