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Inherency In The Prior Art: The Rules Are Becoming Clearer

When is your invention "known" from a prior art reference thus rendering your invention unpatentable? If a prior art reference teaches your invention but does not explicitly recite each and every element, must the presence of the unrecited element, the inherent element, be apparent from reading the reference?

This comment explores recent decisions in the Court of Appeals for the Federal Circuit ("CAFC") regarding the knowledge requirement for one of ordinary skill in the art when inherency is at issue. Although some uncertainty exists, it would appear the CAFC is moving toward the view that inherency does not require recognition by one skilled in the art. In other words, if a feature of a prior art reference is necessarily present in that disclosure, that feature will be found to be inherently disclosed for purposes of anticipation and validity, regardless of whether one of ordinary skill in the art, or even an expert, recognized the existence of that feature in the reference.


A claim is anticipated, and thus invalid, if a single reference, either expressly or inherently, discloses every limitation of the claim at issue. Inherency is predicated on the fact that anticipation cannot be avoided merely because an element is undisclosed and unrecognized in the reference, but is a "deliberate or necessary consequence" of the reference's disclosure. Described another way, an inherent disclosure flows naturally from the teachings of the prior art reference. The Court of Appeals for the Federal Circuit ("CAFC") analyzes inherent disclosures on the basis of requiring an inherency to be "necessarily present" and not merely sometimes, occasionally, or possibly present. At the patent prosecution stage, the United States Patent and Trademark Office similarly requires an examiner to supply an applicant either with a rationale for the inherent disclosure or evidence demonstrating the presence of the inherency.

The relationship between inherency and obviousness is more tenuous. While inherency certainly applies to obviousness determinations, the concepts of obviousness and inherent anticipation are not the same. One court observed that "a retrospective view of inherency is not a substitute for some teaching or suggestion supporting an obviousness rejection." Additionally, "[o]bviousness cannot be predicated on what is unknown." Because the suggestion to combine or modify references must occur prior to an applicant's date of invention, an unknown inherency cannot supply this suggestion at the required time. Later "discovery" of the inherency does not alter the analysis.

Inherency is a factual issue and, as part of an invalidity determination, must be proven by clear and convincing evidence. Extrinsic evidence may be, and indeed should be, used to establish the inherency. The extrinsic evidence used to establish inherency does not have to antedate the critical date of the patent at issue. "Such evidence must make clear that the missing descriptive matter is necessarily present in the thing described in the reference, and that it would be so recognized by persons of ordinary skill." As discussed infra, the CAFC has rendered some important recent decisions regarding whether a party challenging validity must show that one of ordinary skill in the art recognizes an inherent feature as being present in a prior art reference.


The currently prevailing view of the CAFC is that one of ordinary skill in the art is not required to recognize an inherent feature in a prior art disclosure. Schering Corp. v. Geneva Pharmaceuticals, Inc., 339 F.3d 1373 (Fed. Cir. 2003) [hereinafter Schering I], specifically "reject[ed] the contention that inherent anticipation requires recognition in the prior art." In Schering I, the patent at issue, U.S. Patent No. 4,659,716 assigned to Schering Corp. ("'716 patent"), covered the metabolite of the active component in the antihistamine Claritin®. When a patient ingests Claritin®, the active component loratadine is metabolized to descarboethoxyloratadine ("DCL"). The prior art patent, U.S. Patent No. 4,282,233 also assigned to Schering Corp. ("'233 patent"), disclosed only the structure of loratadine; its metabolite was unknown until disclosed by the '716 patent. The lower court held that, while DCL was not expressly disclosed in the '233 patent, the treatment process disclosed therein necessarily produced the conversion of loratadine to its metabolite upon ingestion.

The CAFC agreed with the District Court's inherency determination. Specifically, Schering I refuted the notion that recognition of an inherent feature by one of ordinary skill in the art is, or ever was, a part of an inherent anticipation analysis. Because "DCL necessarily and inevitability forms" when loratadine is ingested by a patient, recognition of the formation can occur at any time. Further, the formation of DCL is not accidental, thus excluding the "716 patent from the protection of such cases as Eibel Process Co. v. Minnesota & Ontario Paper Co., 261 U.S. 45 (1923), and Tilghman v. Proctor, 102 U.S. 707 (1880).

In reaching this result, Schering I carefully distinguished the recognition language in Cont'l Can that has caused confusion for the CAFC in inherency cases. The Schering I panel believed that Cont'l Can stood for the principle that a court may need the assistance of experts in determining factual questions revolving around the inherent disclosure of a prior art reference. Because Cont'l Can did not address the issue of whether recognition was required before or after the critical date of the patent at issue there, the only issue decided by Cont'l Can was that opinions of one of ordinary skill in the art were necessary to determine if the inherency was present in the prior art disclosure. This interpretation seems valid because Cont'l Can remanded that case to the district court wherein "technologists" in the relevant field could aid the district court in identifying the existence of any inherent disclosure in the prior art reference. Cont'l Can did not require, however, that the district court analyze whether the one of ordinary skill recognized the inherency prior to the patent at issue's critical date.

Similarly, cases cited by Schering I have at least alluded to not requiring one of ordinary skill in the art to recognize an inherency. For example, MEHL noted that "[i]nherency is not necessarily coterminous with the knowledge of those of ordinary skill in the art." In In re Cruciferous Sprout Litig., 301 F.3d 1343 (Fed. Cir. 2002) the CAFC held that one of ordinary skill in the art growing the claimed plants would not have to recognize the "sprouting [of] something rich in glucosinolates and high in Phase 2 enzyme-inducing potential." Additionally, Atlas Powder Co. v. Hanex Prods., Inc., 190 F.3d 1342 (Fed. Cir. 1999) noted that "[i]nsufficient prior understanding of the inherent properties of a known composition does not defeat a finding of anticipation."

Thus, Schering I and related cases only require that an inherent feature is necessarily present in the prior art reference. To be necessarily present, one must show more than a mere probability or possibility of the inherent feature's existence. Additionally, it should be noted that not only can individual features of a prior art reference be inherent, but also all limitations of a claim can be inherently disclosed in a single reference.

Another line of CAFC cases has held, however, that one of ordinary skill in the art must recognize the inherent feature of the prior art disclosure. A vacated case indicated that one must show that "the undisclosed information was known to be present in the subject matter of the reference." Noteworthy is the fact that the Elan I majority, Judges Newman and Gajarsa, dissented from the denial of panel or en banc rehearing for Schering I. Specifically, in Schering II, Judge Newman argued that "precedent requires that the missing element was nonetheless known to be present in the subject matter of the reference." Further, in a curious statement, Judge Newman stated that "a previously unknown product does not become unpatentable simply because it existed before it was discovered." Regardless, Judge Newman correctly suggests that an en banc court should have decided the recognition issue, eliminating any questions in the future.

Another CAFC case, Rosco, Inc. v. Mirror Lite Co., 304 F.3d 1373 (Fed. Cir. 2002), apparently required one of ordinary skill in the art to recognize an inherent feature of a prior art reference. The court held that an inherency question is not based on whether a prior art process inherently results in a claimed invention, but "whether one of skilled in the art would read [a prior art reference] as inherently disclosing [an] invention." In Rosco, the patentee's claimed invention covered a mirror having a varying radius of curvature along its major axis. The prior art reference at issue disclosed a production of a mirror and apparently disclosed an inherent varying radius of curvature feature. By following the disclosure, one of ordinary skill in the art would necessarily produce a mirror having a varying radius of curvature. The Rosco panel, however, was more concerned that one of ordinary skill in the art must be able to read the prior art patent "as inherently disclosing a mirror of varying radius of curvature along the major axis. Thus, unlike Schering I, the Rosco panel of Judges Lourie, Plager, and Dyk read Cont'l Can as requiring recognition of an inherent feature of a prior art. Curiously, Schering I fails to mention Rosco in its analysis of recognition of inherent disclosure.

A middle ground exists wherein knowledge by one of ordinary skill may be required in certain circumstances. In EMI Group North America, Inc. v. Cypress Semiconductor Corp., 268 F.3d 1342 (Fed. Cir. 2001), the court noted that requiring one of ordinary skill in the art to recognize the inherent feature in the prior art reference "may be sensible for claims that recite limitations of structure, compositions of matter, and method steps which could be inherently found in the prior art." Because of the requirement that the inherency be necessarily present, recognition may be a factor when determining whether all permeations of a claim limitation are inherently disclosed in a reference. With the facts before EMI Group, however, the court held that recognition was unnecessary because the inherent feature at issue was a law of nature. Schering I also fails to mention EMI Group in its recognition of inherent disclosure analysis.


The problem of determining inherent anticipation also has an interesting twist. At least one CAFC case has treated inherent anticipation as an enablement problem. The Elan panel, in a revised opinion, converted the inherency issue into an enablement problem. The court asserted that Defendant's inherency arguments were more properly construed as enablement arguments. Elan II remanded the case to district court for determination of whether one would need undue experimentation to practice the invention disclosed in the prior art reference.

Alternatively, there are indications that some members of the CAFC consider section 101 to have a broader scope than merely defining patentable subject matter. Under section 101, patentable subject matter only includes a "new . . . process, machine, manufacture, or composition of matter, or any new . . . improvement thereof." At least one case has changed an inherency question into a section 101 question, that is, was what the patentee claimed actually new. In other words, if a patent claiming a prior art composition was found to be valid, the public would have to stop using what has been part of the prior art or risk an infringement suit.

Recently, a CAFC panel summarily rejected this line of thinking. In SmithKline Beechham Corp. v. Apotex Corp., Nos. 03-1285, 03-1313, 2004 WL 868425 (Fed. Cir. April 23, 2004), a panel majority rebuked the concurrence's theory that section 101 includes a review of claim scope. The panel majority noted that a section 101 inquiry is limited to determining whether "the claimed invention represents subject matter eligible for patent protection." As such, claim scope is irrelevant under section 101.

Judge Gajarsa's concurring opinion, however, argued for a determination of whether a claim's scope is truly new under section 101. While not specifically implicating inherency, Judge Gajarsa's argument that a process that naturally reproduces itself is unpatentable under section 101 parallels the argument in Titanium Metal that a patentee cannot claim something that is not new.


So, what is the effect of these rulings? At first glance, it appears that one of ordinary skill in the art is no longer required to recognize that a reference discloses an inherent feature of an invention. A deeper look, however, warrants a more cautious conclusion. Schering I was never heard en banc. While the entire court heard arguments to decide whether an en banc hearing should be allowed, the court only denied the en banc hearing. In accordance with CAFC rules, the Schering I decision is thus only precedential as far as its panel is concerned. The situation in the Elan line of cases only adds to the confusion. While Elan I was overruled en banc, no reason for the decision to overrule was given in the opinion. As a result, practioners must live with the possibility that CAFC panels not comprised of the Schering I judges, for example a panel comprising Judges Newman and Gajarsa, are free to follow their own precedents, which may include knowledge requirements in inherency cases.

Further, the CAFC has an established rule that earlier decisions of a panel are binding upon that panel unless overruled en banc. Thus, for example, the Newman, Gajarsa, and Dyk panel has, because of Elan II, a binding decision that converts a patentee's lack of inherent anticipation argument into an enablement analysis under section 112. Because of cases like Titanium Metals, the status of patentability under section 101 also remains in question.


Schering I and Toro decided that inherency does not require recognition in the art, which seems to reflect common sense and should make the lives of patent practitioners a bit more certain. These recent CAFC decisions are based upon a simple point: an inherent feature of a prior art disclosure is always present regardless of whether one of ordinary skill in the art, or even an expert, recognizes the inherent feature's existence. As noted in Atlas Powder, "[t]he public remains free to make, use, or sell prior art compositions or processes, regardless of whether or not they understand their complete makeup or the underlying scientific principles which allow them to operate." Novelty demands a higher threshold than merely permitting an "inventor" to discover what already exists in an unknown state. While the inventor's discovery may constitute a valuable contribution to science, it should not constitute patentable subject matter.

Unfortunately, though, as is often the case, the guidance from the CAFC is not yet entirely clear regarding inherency assessments, in that additional CAFC opinions still suggest that recognition in the art is sometimes required or that some other section of the Patent Act applies.

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