Court Opinion

ID: 9622721
Source: CourtListenerOpinion
Date Created: 2023-08-22 06:22:34.68539+00
Date Added: 2024-06-11T17:37:02.106784
License: Public Domain

LINN, Circuit Judge,
concurring-in-part and dissenting-in-part.
I am pleased to join Part III of the majority opinion affirming the judgment of noninfringement, but I respectfully dissent from Part II affirming the district court’s inequitable conduct ruling. With regard to Parts I and IV, I concur in the result and with much of the majority’s reasoning in affirming the judgments of obviousness and anticipation, but I write separately to express my disagreement with the majority’s unnecessary, and in my view improper, reference in this case to the claims of the prior art as a measure of what the prior art discloses.
I. Inequitable Conduct
This case involves attorney arguments submitted to the EPO in the '636 patent (the European counterpart of the '382 patent) over its interpretation, which allegedly refute, or are inconsistent with, arguments submitted to the PTO in the '551 patent over the interpretation of the same language. The question for purposes of materiality here is not whether Abbott’s arguments to the PTO were meritorious (i.e., that the word “preferably” in the '382/'636 patent would actually have been interpreted by a skilled artisan to mean “required”); rather, the question is whether anything in Abbott’s EPO submissions “refutes, or is inconsistent with,” its arguments to the PTO. 37 C.F.R. § 1.56(b)(2) (2009). Even if this information were material, however, the individuals who owed a duty of disclosure to the PTO produced a good faith explanation as to why they withheld the EPO submissions. Far from a mere blanket denial of deceptive intent, the individuals’ explanation includes specific, detailed reasons as to why they subjectively believed that the withheld information was immaterial during prosecution. Such an explanation will defeat a charge of inequitable conduct if it is “plausible.” The question, thus, is not whether it is plausible that the information is immaterial—a question asked under the objective materiality prong—but rather, whether it is plausible that the individuals subjectively believed that the reference was immaterial at the time they withheld it-a question presented under the subjective intent prong.
I address these questions in turn.
A. Materiality
In Scanner Technologies Corp. v. ICOS Vision Systems Corp., 528 F.3d 1365 (Fed.Cir.2008), we stated:
Whenever evidence proffered to show either materiality or intent is susceptible of multiple reasonable inferences, a district court clearly errs in overlooking one inference in favor of another equally reasonable inference. All reasonable inferences must be drawn from the evidence, and a judgment then rendered on the evidence as informed by the range of reasonable inferences. Where the rule is breached, no inequitable conduct may be found. The rule is necessary, for without it findings of inequitable conduct, with the punishment of unenforceability of the entire patent, could wrongly stand.
Id. at 1376 (footnote omitted). In that case, an applicant asked the PTO to expedite the handling of its application in view of an allegedly infringing device on the market. The applicant told the PTO that it had made a “rigid comparison” of the device with the claims of the application, and that the device was on “open display” at a trade show. Id. at 1372. The district court found these statements materially misleading. It inferred from these state*1313ments that the applicant had actually seen the accused device when, in fact, the device was in a black sealed box and an inspection of it would not have revealed how the device meets the limitations of the claims. Although we acknowledged that the district court’s interpretation of this language was “not unreasonable,” we ultimately reversed, holding that, under an equally reasonable favorable interpretation, a “rigid comparison” would not require physical inspection, and that the device was on “open display” in the sense that the black box was located in a public, as opposed to private, setting. Id. at 1376-77.
Accordingly, a district court “overlooks” a favorable inference, within the meaning of Scanner Technologies, not simply when it ignores or fails to mention the possibility of such an inference, but when it actually “adopt[s] an unfavorable inference ... over an equally reasonable favorable inference.” Id. at 1377. Citing this rule, we have stated that an unfavorable inference “must not only be based on sufficient evidence and be reasonable in light of that evidence, but it must also be the single most reasonable inference able to be drawn from the evidence to meet the clear and convincing standard.” Star Scientific, Inc. v. R.J. Reynolds Tobacco Co., 537 F.3d 1357, 1366 (Fed.Cir.2008) (emphasis added) (citing Scanner Techs., 528 F.3d at 1376).
I believe that the “rule” of Scanner Technologies has been breached in this case. The submissions made by Abbott to the EPO are susceptible of multiple reasonable inferences and, depending on the inference drawn, may or may not be material. In each instance, the district court inferred one meaning from the EPO submissions, rendering them material, when an equally reasonable (if not more reasonable) inference renders them immaterial.
The district court found that Abbott’s “submissions made to the EPO were inconsistent with the submissions made to the PTO in at least two important ways.” Trial Opinion, 565 F.Supp.2d at 1109.1 First, in the district court’s words, “The EPO was told that under the '382 a protective membrane was merely preferred and not required when dealing with live blood and specifically quoted the ‘optionally, but preferably’ sentence in support.” Id. at 1109-10 (emphases in original). Second, “The EPO was told that the critical sentence was ‘unequivocally clear’ and taught skilled artisans that ‘the protective membrane [was] optional, however it is preferred when used on live blood____’ ” Id. at 1110 (alteration and omission in original).
In my view, the district court arrived at these two findings in error. I address these findings in turn.
1. “merely preferred and not required”
The first clearly erroneous finding inappropriately attributes to Abbott statements that it did not make. Abbott never said that the membrane was “merely preferred” or “not required” when dealing with blood. Such a statement would be devastating to Abbott and would clearly be material. Instead, Abbott’s EPO submissions simply quoted the “[o]ptionally, but preferably” sentence from the '382/'636 *1314patent and, tracking closely the just-quoted language, stated that the protective membrane is “preferably to be used with in vivo measurements” and is “preferred when used on live blood.” J.A. 6531, 6585. The word “preferably” is the very same word used in the '382/'636 patent. Abbott never said “merely preferred,” and it certainly never said “not required.” Nor did Abbott ever use any synonym that might have shed some light on the meaning of the word as used in the patent. Instead, Abbott used the very same word (preferably) in the very same context (blood) as the word appears in the '382/'636 patent. Because Abbott’s submissions to the EPO tracked the very language of the '382/'636 patent, they add nothing to the meaning of the word “preferably” beyond what was already before the examiner in the '382/ '636 patent.2
If anything, the EPO submissions bolster, rather than refute, Abbott’s argument to the PTO that a protective membrane was thought by persons of ordinary skill to be required for use in blood. One of the EPO submissions explains that the protective membrane serves to “prevent the larger constituents of the blood, in particular erythrocytes, from interfering with the electrode sensor.” J.A. 6585. Indeed, it is this very function that makes it a “protective” membrane: the membrane protects the electrodes from fouling caused by the larger constituents found in blood.3 The EPO Board itself, upon reviewing Abbott’s submissions, recognized as much when it held: “The Board can therefore agree with the Appellant that by a protective membrane is meant exercising a filtering function, preventing the grosser components of blood from reaching the electrode....” J.A. 6570-71. Given that the Board itself recognized that the protective membrane serves an important “filtering function” in blood, it cannot be said that Abbott’s EPO submissions somehow denigrated the role of a protective membrane when used on blood.4
It is important to appreciate that, aside from testing on “blood,” the sensor recited in claim 1 of the '636 patent is also claimed for testing on “interstitial fluid.” Interstitial fluid does not contain those larger constituents in blood that cause fouling of the sensor’s electrodes. Because the larger constituents are absent in interstitial fluid, all parties agree that a protective membrane is optional when the sensor is used to test interstitial fluid.5 It is therefore reasonable to interpret the word “optionally,” in the phrase “[o]ptionally, but preferably when used on live blood,” as governing those situations in which the *1315fluid being tested is something other than blood, such as interstitial fluid.6
Abbott’s submissions to the EPO do not contradict this interpretation. Abbott never said that the membrane is optional all the time, in all fluids, or under all conditions. Rather, Abbott said that the membrane is “optionally utilized with the glucose sensor of the patent in suit,” J.A. 6530-31 (emphasis added), more specifically, “claim 1 of the patent in suit,” J.A. 6530 (emphasis added). Claim 1 of this patent recites, in the disjunctive, “blood or interstitial fluid.” No claim is directed to blood alone.7 Abbott’s EPO submissions can therefore be interpreted, consistent with the quoted “[ojptionally, but preferably” sentence, to mean that a protective membrane is used “preferably” on blood, and “optionally” on fluids other than blood, such as interstitial fluid. And again, the word “preferably” is not defined in the EPO submissions or otherwise explained, except to say that the membrane serves to “prevent the larger constituents of the blood, in particular erythrocytes, from interfering with the electrode sensor”—a statement that tends to support, rather than refute, Abbott’s argument to the PTO. J.A. 6585.
But instead of giving Abbott the benefit of a reasonable favorable interpretation, in which the words “optionally” and “preferably” are directed to interstitial fluid and blood, respectively, the district court drew a negative inference by extending the word “optionally” to govern both interstitial fluid and blood, collectively. In this way, the district court inferred from Abbott’s EPO submissions that a membrane was “not required when dealing with live blood”—language that Abbott itself never used in its submissions. Trial Opinion, 565 F.Supp.2d at 1109 (emphasis in original). By adopting one inference (i.e., “optionally” governs both blood and interstitial fluid) over an equally reasonable favorable inference (i.e., “optionally” governs interstitial fluid, and “preferably” governs blood), the district court, in my view, clearly erred.
2. “unequivocally clear”
The second clearly erroneous finding concerns Abbott’s submission to the EPO that “[i]t is submitted that this disclosure is unequivocally clear.” J.A. 6585. The district court found this statement to be inconsistent with Abbott’s argument to the PTO that the word “preferably,” as used in the patent’s “[ojptionally, but preferably” sentence, was not being used in a colloquial sense (to express a mere preference) but rather constituted “patent phraseology” (to express a requirement). Because Abbott had told the EPO that “this disclose is unequivocally clear,”8 the district *1316court inferred from this submission that that each and every word of the “[optionally, but preferably” sentence must carry its plain and ordinary meaning.
While plausible, the district court’s inference is not the only inference that can reasonably be drawn from Abbott’s submission. Abbott did not say that any specific word is unequivocally clear. Rather, what was said to be unambiguously clear is “this disclosure”—i.e., the full quoted sentence from the '382/'636 patent, which reads:
Optionally, but preferably when being used on live blood, a protective membrane surrounds both the enzyme and the mediator layers, permeable to water and glucose molecules.
This sentence sets forth two functional characteristics of the membrane: (1) it is “protective,” and (2) it is “permeable to water and glucose molecules.” It is these two functional characteristics that Abbott, in its argument, went on to describe immediately after calling this disclosure “unequivocally clear.”9 First, with regard to the membrane being “protective,” Abbott told the EPO that its membrane serves “to prevent the larger constituents of the blood, in particular erythrocytes from interfering with the electrode sensor.” J.A. 6585. Second—or in Abbott’s words “[furthermore”10—the membrane is “permeable” to glucose molecules because it “should not prevent the glucose molecules from penetration.” J.A. 6585. These two concepts, as articulated in Abbott’s submission, flow directly from the quoted sentence of the '382/'636 patent, in the same order that they appear in that sentence. It is reasonable to read Abbott’s argument as saying no more than what is “unambiguously clear,” in the quoted sentence, is that the membrane serves the dual roles of preventing larger constituents in blood from interfering with the electrode sensor, while also allowing smaller water and glucose molecules to pass through.
The district court believed that only this second function, glucose permeability, was necessary to distinguish the Dl reference *1317in the EPO proceeding, and that Abbott’s argument to the EPO “plainly went beyond this point of distinction and submitted that it was ‘unequivocally clear’ that the '382/'636 needed no membrane at all for use with blood.” Trial Opinion, 565 F.Supp.2d at 1116. But Abbott never told the EPO that the '382/'636 patent “needed no membrane at all for use with blood.” Those are the district court’s words, not Abbott’s. Moreover, the fact that the '382/'636 patent can optionally be used with or without a “protective” membrane in some glucose-containing fluids, like interstitial fluid, was indeed an important point of distinction that ultimately convinced the EPO Board that the '382/'636 patent did not possess a “diffusion-limiting” membrane like that of the D1 reference.11 The D1 reference requires a diffusion-limiting membrane because its sensor cannot handle a rapid influx of glucose molecules. The pores of this membrane are small enough to partially reduce the flow of glucose molecules and to completely block the much larger blood constituents, like erythrocytes. The '382/'636 patent, by contrast, has no problem with a rapid influx of glucose molecules, so it does not need a diffusion-limiting membrane, only a protective membrane to protect against fouling by larger blood constituents. But the fact that the '382/'636 patent even discloses the use of a protective membrane shows that no diffusion-limiting membrane was present in the '382/'636 patent. If it were present, then the diffusion-limiting membrane would itself block larger blood constituents, thus rendering a protective membrane entirely redundant and unnecessary. The EPO Board understood this exact point, stating: “Common sense dictates moreover that the optional presence of a protective membrane would be unnecessary if a diffusion controlling membrane was present.” J.A. 6571. In other words, the presence of a protective membrane, which performs the erythrocyte-filtering function of a diffusion-limiting membrane, implies the absence of a diffusion-limiting membrane. The EPO Board therefore agreed with Abbott that the '382/'636 patent did not possess a diffusion-limiting membrane like the one in the D1 reference, which was precisely the point Abbott was trying to make.
By adopting one inference (i.e., what is “unambiguously clear” is the meaning of each individual word) over an equally reasonable favorable inference (i.e., what is “unambiguously clear” is the functional role of the membrane), the district court again, in my view, clearly erred.
The foregoing interpretation of the ambiguous language in Abbott’s EPO submission is, in my view, at least as reasonable as the district court’s and the majority’s. This favorable interpretation, unlike the contrary interpretation, does not rely on individual words or phrases in isolation, but properly views them in context: looking to the surrounding text in which those words and phrases appear, with an eye towards the purpose for which the arguments were submitted during prosecution, and is ultimately consistent with the way the arguments were interpreted by the EPO Board. As shown with regard to each substantive point in the foregoing materiality analysis, and with all due respect to my colleagues in the majority, this favorable interpretation was not invented on appeal; each point was argued to the district court.
*1318The majority concludes that Abbott’s EPO statements “cannot possibly be read in this manner,” because the “unequivocally clear” statement is “tied directly to the optional nature of the membrane.” Maj. Op. 1304. For this proposition, the majority focuses on the “three sentences in question” in the EPO submission: (1) the “[ojptionally, but preferably” sentence quoted from the '382/'636 patent; (2) the first sentence of a nine-sentence paragraph that reads, “It is submitted that this disclosure is unequivocally clear”; and (3) the second sentence of this paragraph that reads, “The protective membrane is optional, however, it is preferred when used on live blood in order to prevent the larger constituents of the blood, in particular erythrocytes from interfering with the electrode sensor.” There are seven more sentences in this paragraph, overlooked by the majority, that are dedicated to describing the glucose-permeability function of the membrane. See supra note 8. As previously discussed, it is reasonable to read this full paragraph as saying that what is “unambiguously clear” (first sentence) is that the protective membrane performs the dual functions of filtering erythrocytes in blood (second sentence) while allowing glucose to pass through (third through ninth sentences).
Instead of reading the paragraph as a whole, the majority links the paragraph’s topic sentence (“unambiguously clear”) only to the first five words of the second sentence (“The protective membrane is optional .... ”). The majority then ascribes the word “optional” to whole blood and the word “preferred” to live blood. It then concludes—“[njecessarily”—that “the membrane was not required for either whole blood or live blood.” Maj. Op. 1304. Each of these three logical steps is based on inference, and at each step, I believe the majority has inappropriately drawn an inference against the patentee.
First, the phrase “[t]he protective membrane is optional” says nothing of blood. As a general statement, moreover, it is factually correct: the membrane is optional in certain fluids, like interstitial fluid, which do not contain erythrocytes. As previously discussed, the fact that the protective membrane is optional in some glucose-containing fluids, like interstitial fluid, shows that the '382/'636 patent does not possess a diffusion-limiting membrane like the one in the D1 reference. The majority entirely misses this point.
Second, live blood is a species of whole blood; both contain all of the larger constituents of blood, including erythrocytes. Because both live and whole blood contain erythrocytes, the latter half of the second sentence describing the membrane’s filtering function—i.e., “in order to prevent the larger constituents of the blood, in particular erythrocytes from interfering with the electrode sensor”—applies equally to both types of blood. The majority, however, distinguishes whole blood from live blood and places the former into the “optional” category while retaining the latter under the “preferred” category. But nothing in this paragraph suggests any distinction between whole and live blood, as both contain erythrocytes. Moreover, to the extent that the majority relies on such a distinction for purposes of materiality, it fatally undermines the finding of deceptive intent: Attorney Pope testified that he considered the terms “whole blood” and “live blood” to be synonymous. Trial Tr. 629. The district court made no finding that Attorney Pope did not actually possess this belief, or even that this belief was unreasonable. Instead, the district court dismissed Attorney Pope’s mistaken belief because “th[e] EPO submissions represented that a membrane was merely optional when used with blood.” Trial Opinion, 565 F.Supp.2d at 1114 (em*1319phases added). This statement lumps together both live and whole blood under the “optional” category. The majority, however, relies on this distinction and ascribes the word “optional” to whole blood and the word “preferred” to live blood. Maj. Op. 1304 (“[Tjhe membrane was optional (lohole blood and other fluids) or preferred (live blood).” (emphases added)). Because the majority relies on this distinction for purposes of materiality, Attorney Pope’s honest but mistaken belief would serve as additional exculpatory evidence under the intent prong.
Third, the majority concludes that, irrespective of whether the membrane was “optional” or “preferable” in either whole or live blood, it “[njecessarily” follows that the membrane was “not required for either whole blood or live blood.” Id. (emphases added). It is unclear how the majority arrives at this conclusion. The question here is not what the word “preferably” means in isolation but whether anything in Abbott’s EPO submissions, which quotes and tracks the very language in the '382/ '636 patent, contradicts Abbott’s argument to the PTO. And again, Abbott never told the EPO that the membrane is “not required” for use in blood; nor did it use any synonym for the word “preferred.” Because the EPO submissions explain that the membrane serves to protect the sensor from erythrocytes found in whole blood, these submissions tend to bolster rather than refute Abbott’s arguments to the PTO.
A final point deserves brief comment. The majority invokes the familiar adage that “[cjlose cases should be resolved by disclosure.” LaBounty Mfg., Inc. v. U.S. Int’l Trade Comm’n, 958 F.2d 1066, 1076 (Fed.Cir.1992) (emphasis added). It is sage advice, and practitioners should take it to heart, so that they may avoid even being accused of inequitable conduct, much less being found to have committed it. But this adage is not a legal rule. We have never recognized a “close case” standard for materiality. The majority, however, believes that if this is such a case, then the duty of disclosure “requires that the material in question be submitted to the examiner.” Maj. Op. 1305 (emphasis added). Our circuit already entertains five different standards for materiality. See Digital Control, Inc. v. Charles Mach. Works, 437 F.3d 1309, 1315-16 (Fed.Cir.2006). I do not think that we need a sixth.
B. Intent
“[Ijnequitable conduct requires not intent to withhold, but rather intent to deceive.” Dayco Prods., Inc. v. Total Containment, Inc., 329 F.3d 1358, 1367 (Fed. Cir.2003). The requisite level of intent is “specific intent”—not simple negligence, or even gross negligence. Star Scientific, 537 F.3d at 1368; Kingsdown Med. Consultants, Ltd. v. Hollister Inc., 863 F.2d 867, 876 (Fed.Cir.1988) (en banc) (holding even gross negligence insufficient to prove intent to deceive). As recognized by the Supreme Court and virtually every circuit, “specific intent” denotes a subjective rather than objective standard and is generally associated with actions deliberately and consciously taken to achieve a specific result.12
*1320Consistent with this subjective standard, “[ijntent to deceive cannot be inferred simply from the decision to withhold the reference where the reasons given for the withholding are plausible.” Dayco, 329 F.3d at 1367 (emphases added). One “reason” that a reference may legitimately be withheld is that the “applicant did not know of its materiality.” FMC Corp. v. Manitowoc Co., 835 F.2d 1411, 1415 (Fed.Cir.1987) (emphasis added). It is this lack of knowledge, or one’s subjective belief that the reference was immaterial, that a court must assess as either plausible or implausible for purposes of specific intent. Thus, when assessing an applicant’s reason for withholding a reference that he or she believed was immaterial, the question is not, “Is it plausible that the reference is immaterial?” That question belongs under the objective materiality prong, to be evaluated “on the evidence as informed by the range of reasonable inferences” both for and against materiality. Scanner Techs., 528 F.3d at 1376. Rather, the question for purposes of specific intent is, “Is it plausible that the applicant subjectively believed that the reference was immaterial?” This inquiry properly focuses on what the applicant knew or believed to be true about the reference at the time that he or she decided to withhold it.
In this case, it is significant that Attorney Pope and Dr. Sanghera were not aware of what the district court called the “one exception” in the prior art—U.S. Patent No. 4,388,166 (“Suzuki”)—of a membraneless sensor used on whole blood. Trial Opinion, 565 F.Supp.2d at 1099 & n. 6, 1106 n. 12. If they had known of Suzuki, it would have significantly undercut their argument to the PTO that persons of ordinary skill believed that membranes were required for use on whole blood. Moreover, if they had known of Suzuki, it would have made it far more difficult for them to explain why they interpreted the EPO submissions in a manner contrary to Suzuki. But, unlike Suzuki, all prior art of record and all prior art of which Attorney Pope and Dr. Sanghera were aware uniformly showed that “those skilled in the art typically employed a membrane on a sensor used with live or whole blood.” Id. at 1099. It is therefore entirely plausible that Attorney Pope and Dr. Sanghera subjectively believed that the EPO discussion of the '382/'636 patent—just like all other prior information known to them—did not contradict the use of membranes for testing on whole blood.
Nor did Attorney Pope or Dr. Sanghera have any knowledge that one of the inventors, Dr. Higgins, held a contrary view of the “[ojptionally, but preferably” language. Attorney Pope did not draft the original specification, and the two did not discuss this language with Dr. Higgins when they submitted their argument to the PTO. As we have made clear, “no duty to inquire arises unless counsel is on notice of the likelihood that specific, relevant, material information exists and should be disclosed.” Brasseler, U.S.A. I, L.P. v. Stryker Sales Corp., 267 F.3d 1370, 1383 (Fed.Cir.2001) (emphases added). “The mere possibility that material information may exist will not suffice to give rise to a duty to inquire.” Id. at 1382 (emphasis added). Here, the record does not show, and no party has argued, that Attorney Pope and Dr. Sanghera were on notice, at the time of the withholding, of the likelihood that Dr. Higgins held a different view of the “[ojptionally, but preferably” language. To the contrary, it appears that Dr. Higgins formulated his opinion of this particular language for the first time in the present litigation. Dr. Higgins’s personal opinion is therefore entirely irrelevant to what Attorney Pope and Dr. Sanghera subjectively believed at the time of the withholding.
*1321Nor is there any dispute that Dr. Sanghera was perfectly qualified to submit an expert declaration to the PTO as to the meaning of the “[ojptionally, but preferably” language. As the district court found, “a person of ordinary skill in the art would have had a doctoral degree or postgraduate experience working toward a Ph.D” and “would also have had some level of experience in actually constructing electrochemical sensors or would at least be familiar with them.” Trial Opinion, 565 F.Supp.2d at 1100 n. 8. Dr. Sanghera had earned a Ph.D in Electrochemical Bio-sensors and had worked in the research and development of biosensors for over ten years by the time he submitted his declaration to the PTO in 1997. J.A. 7636. Although he did not possess these qualifications in 1983 (the invention date of the '551 patent), this fact would not disqualify him from giving a competent opinion in 1995 as to what a hypothetical person of ordinary skill would have known in 1983. See Endress + Hauser, Inc. v. Hawk Measurement Sys. Pty. Ltd., 122 F.3d 1040, 1042 (Fed.Cir.1997) (stating that the “person of ordinary skill in the art” in § 103 is a “theoretical construct ... and is not descriptive of some particular individual”). In his declaration, Dr. Sanghera fully disclosed his qualifications and his employment with the assignee, Medisense (now Abbott). J.A. 7636. He also testified that he had thoroughly searched the prior art for any information that might contradict his declaration. Trial Tr. 709-10. There is no suggestion, much less any finding by the district court, that Dr. Sanghera did not actually perform this search or that it was not made in good faith.
With regard to the foregoing, the majority correctly acknowledges: (1) that it is “undisputed” that Attorney Pope and Dr. Sanghera were unaware of the existence of either the Suzuki reference or Dr. Higgins’s contrary interpretation, (2) that the district court did not base its finding of intent on the existence of such knowledge, and (3) that it did not find that Dr. Sanghera was unqualified or misrepresented his credentials. Maj. Op. 1308. While calling these facts “irrelevant,” id. 1308, the majority nevertheless “finds support” for the district court’s finding of intent based on these very facts, namely, that “Pope relied on Dr. Sanghera, who was not a person having ordinary skill in the art at the time of the '382 patent, ... rather than the inventors of the patent, who appear to have had a view quite contrary to Abbott’s,” id. 1307. Indeed, far from being “irrelevant,” any facts tending to show what Attorney Pope and Dr. Sanghera did or did not know during prosecution are critical to discerning their intent and the plausibility of their explanation. All available evidence regarding an individual’s mental state, particularly facts “pointfing] away from an intent to deceive,” must be weighed when assessing culpable intent. Akron Polymer Container Corp. v. Exxel Container, Inc., 148 F.3d 1380, 1384 (Fed.Cir.1998) (stating that “requisite weight ... must be given” to evidence of good faith). The fact that these individuals were unaware of any information that would contradict their argument to the PTO, despite having performed a prior art search (a search that they had no obligation to perform) for the specific purpose of ensuring the validity of their argument, is evidence of good faith. But the district court expressly “found no[J” evidence of good faith and dismissed any “possible inferences of good faith.” Trial Opinion, 565 F.Supp.2d. at 1114. It necessarily gave no weight to any favorable inference.
The district court rejected Attorney Pope’s and Dr. Sanghera’s good faith explanations as “not plausible” and “unconvincing.” While considerable deference is *1322owed to a trial court’s credibility determinations, this does not mean that a trial court can “cloak the application of an erroneous legal standard in the guise of a credibility determination, and thereby shield it from appellate review.” Andreu v. Sec’y of Dep’t of Health & Human Servs., 569 F.3d 1367, 1379 (Fed.Cir.2009). Indeed, on closer examination, it becomes apparent that the district court simply disagreed with Attorney Pope’s and Dr. Sanghera’s interpretation of the EPO submissions. The district court’s opinion reflects that what proved “unconvincing” to the court was not the truthfulness of the witnesses’ subjective beliefs, but rather the notion that the submissions were not in fact material.
Attorney Pope testified that he believed the EPO submissions to be cumulative of the '382/'636 patent because those submissions quoted and tracked the very same “[ojptionally, but preferably” language in the '382/'636 patent, and that the word “preferably,” read in context of the entire '382/'636 patent, meant that the protective membrane was required in whole blood. Trial Tr. 640-41, 643, 645-47. As a patent attorney with over thirty years of professional experience, Attorney Pope testified that, when drafting and prosecuting applications, practitioners often use the word “preferred” rather than “required” in order to avoid a disclaimer of claim scope. Trial Tr. 632 (testifying that “[i]f the specification says ‘y°uust,’ then you’ve now precluded yourself from ever claiming more broadly”). See, e.g., Andersen Corp. v. Fiber Composites, LLC, 474 F.3d 1361, 1372 (Fed.Cir.2007) (construing product claim as product-by-process claim because the specification used “language of requirement, not preference ” (emphases added)); Chimie v. PPG Indus., Inc., 402 F.3d 1371, 1385 (Fed.Cir.2005) (construing claim to require unrecited feature where applicant told examiner that such feature “must be used” (emphasis added)). In his view, the earlier EPO submissions did not contradict his argument to the PTO regarding the meaning of the word “preferably,” because those submissions themselves explain why a membrane is “preferred” (i.e., “required”) in whole blood: “to prevent the larger constituents of the blood, in particular erythrocytes from interfering with the electrode sensor.” Trial Tr. 676-77 (quoting May 23, 1995 EPO submission). Thus, Attorney Pope believed that the EPO submissions were not material because they were both cumulative of the '382/'636 patent and not inconsistent with the PTO submissions.
This explanation is not conclusory. It relies on specific statements and information in the references, and it specifically provides that this was the reason why, at the time, the information was not disclosed to the PTO. Such an explanation is a far cry from a “mere denial of intent to mislead (which would defeat every effort to establish inequitable conduct).” FMC Corp., 835 F.2d at 1416. Compare Praxair, Inc. v. ATMI, Inc., 543 F.3d 1306, 1317-18 (Fed.Cir.2008) (affirming finding of deceptive intent where attorney’s explanation failed to “suggest that, at the time of the prosecution of the '115 patent, he believed that disclosure of the RFO art would have been cumulative; he also does not actually state that the alleged cumulativeness was the reason he failed to disclose prior art RFO devices to the PTO; and he was unable to identify any specific reference that rendered the RFOs cumulative” (emphases added)), with In re Harita, 847 F.2d 801, 806-07 (Fed.Cir.1988) (reversing finding of deceptive intent where Japanese patent agent explained that he believed, at the time, there was no duty to disclose to the PTO prior art dis*1323covered after filing, as was the practice in Japan).
“Intent to deceive should be determined in light of the realities of patent practice, and not as a matter of strict liability whatever the nature of the action before the PTO.” N. Telecom, Inc. v. Datapoint Corp., 908 F.2d 931, 939 (Fed.Cir.1990). Here, the trial court’s disagreement with Attorney Pope centered not on his subjective understanding of the facts but rather on the court’s normative view of the law. First, in dismissing his explanation that the word “preferably” in the context of the '382/'636 patent means “required,” the district court stated, “Words are supposed to mean what they say. Otherwise, our patent-disclosure system would collapse.” Trial Opinion, 565 F.Supp.2d. at 1114. But we have long recognized that “patentees frequently use terms idiosyncratically,” which is why persons of ordinary skill must look to the full context in which a term is used. Phillips v. AWH Corp., 415 F.3d 1303, 1314 (Fed.Cir.2005) (en banc). The district court’s second reason for dismissing Attorney Pope’s explanation was that, “since the claims of the '382 covered membraneless sensors used in blood, as both sides agree, the specification must have been sufficient to support the membraneless sensors.” Trial Opinion, 565 F.Supp.2d. at 1114 (emphases in original). I find this reasoning flawed. It presupposes that the specification of the '382 patent enabled such a “membraneless sensor[ ] for use in blood”—a fact that Abbott fiercely disputes. See Br. of Pl.-Appellant 14-15. Moreover, it relates to a product that is not specifically claimed in the '382 patent. See '382 patent cl.l (claiming “[a] sensor electrode for use in a liquid mixture of components ”—not specifically blood (emphasis added)). The district court concluded, “At all events, ... the fact remains that ‘preferred’ does not mean ‘required,’ which was a point made in the EPO appeal.” Trial Opinion, 565 F.Supp.2d. at 1114. This statement is circular, and it again shows that the district court anchored its assessment of Attorney Pope’s subjective beliefs to the court’s previous finding of objective materiality.13
The majority does not deny that the district court found the individuals’ good faith explanations “not plausible” and “not credible” in light of its prior finding of objective materiality. Moreover, the majority itself rejects these good faith explanations based on the very same “plain English” rationale on which it affirms the materiality finding. Compare Maj. Op. 1304-05 (affirming materiality based on “plain English reading” of isolated words), with id. 1306-07 (rejecting good faith explanation because it contradicts “normal English” meaning of isolated words).14 Respectfully, this rationale misses the point as it relates to the question of intent. Attorney Pope testified that he read the “[ojptionally, but preferably” language, not in isolation, but “in the context of the *1324entire document,” and that he “would never attempt to understand something drawn out of a document standing alone.” Trial Tr. 668. That Attorney Pope actually read these words in context, rather than in isolation, has not been disputed. The isolated “plain English” meaning of those words, therefore, has little bearing on the plausibility of his subjective belief regarding his understanding of the EPO submissions.
In my view, Attorney Pope and Dr. Sanghera’s good faith explanations are entirely consistent with the alternative reasonable interpretation of the EPO submissions that renders them immaterial. Indeed, as demonstrated by the myriad footnote citations to the trial record, supra, this alternative reasonable interpretation is the one that the individuals’ themselves presented to the district court. Coupled with the fact that these individuals were unaware of the Suzuki patent (or any other contrary teachings), their explanations are certainly plausible.
It bears repeating that what is “plausible” here, for purposes of specific intent, is that the individuals subjectively believed that the withheld information was immaterial when they withheld it. This answers a different question than the one the district court appeared to ask, which was whether it is plausible that the withheld information was not in fact material—a test more appropriately considered under the objective materiality prong. To the extent that the district court assessed the plausibility of the individuals’ subjective beliefs based on the objective reasonableness of those beliefs, or otherwise required their mistake to be reasonable in order to defeat a finding of specific intent, it did so in violation of Kingsdown, 863 F.2d at 876 (holding even gross negligence insufficient to prove intent to deceive).
Because I am left with a definite and firm conviction that a mistake has been committed with respect to both materiality and intent, I would reverse the district court’s inequitable conduct ruling.
II. Invalidity
I agree with the majority that the prior art '382 patent renders the claims of the '551 patent obvious (Part I of majority opinion) and that the prior art '225 patent anticipates the claims of the '745 patent (Part IV of majority opinion). The descriptive portions of the prior art patents are alone sufficient to invalidate the claims-in-suit. It is therefore unnecessary, and I believe improper in this case, to look to the claims of the prior art patents as a measure of what the prior art discloses for purposes of obviousness and anticipation. See In re Benno, 768 F.2d 1340, 1346 (Fed.Cir.1985) (“The scope of a patent’s claims determines what infringes the patent; it is no measure of what it discloses.”). Here, although the claims of the prior art '382 and '225 patents are broad enough to cover a membraneless sensor and a diffusible redox mediator, respectively, those structures are not specifically recited in the claims but instead are disclosed in the descriptive portions of the specification.
The majority quotes Benno as follows: “[I]t is true ... that ‘a claim is part of the disclosure’....” Maj. Op. 1295. But the internal quotation is attributed to the PTO Solicitor and overlooks the more relevant statements made by the court immediately before and after it. The court’s full quotation reads:
Samuel F.B. Morse, the inventor of the telegraph, had a patent thereon, issued in 1840, containing a claim (which the Supreme Court held invalid) which was broad enough to read on the modern *1325Telex. By the board’s reasoning, Morse’s telegraph patent therefore would have made the Telex obvious. The scope of a patent’s claims determines what infringes the patent; it is no measure of what it discloses. A patent discloses only that which it describes, whether specifically or in general terms, so as to convey intelligence to one capable of understanding. While it is true, as the Solicitor suggested at oral argument, that “a claim is part of the disclosure,” that point is of significance principally in the situation where a patent application as filed contains a claim which specifically discloses something not disclosed in the descriptive part of the specification (claims being technically part of the “specification,” 35 USC 112, 2d par.), in which case the applicant may amend the specification without being charged with adding “new matter,” within the meaning of § 132. But that is not the situation here. Danti’s claim 1 does not disclose any structure additional to what the Danti specification discloses.
Benno, 768 F.2d at 1346 (emphases added; internal citations omitted). The court went on to reverse the Board’s rejections over the prior art Danti patent.
Here, the claims of the '382 and '225 patents do not specifically disclose a membraneless sensor or a diffusible redox mediator; those structures are instead disclosed in the descriptive parts of the specifications. It is also unclear whether the claims on which the majority relies were originally present in the applications that resulted in the '382 and '225 patents or whether they were added during prosecution, which may affect their prior art date.
The other cases cited by the majority to justify its reference to the claims of the prior art patents are not on point. In In re Smolak, 24 C.C.P.A. 1132, 88 F.2d 838, 840 (1937), it was appropriate to look to the claims of a reference patent for a disclosure of a “press molded” limitation because, “[t]he words ‘press molded’ appear only in the claims of the reference.” In Gabrielidis v. Prince Sports Group, Inc., 2000 WL 1648134, at *7 (Fed.Cir. Nov. 1, 2000) (non precedential), we held that certain elements were not disclosed anywhere in the reference patent, either in the claims or in the remainder of the specification, and therefore affirmed the denial of summary judgment of anticipation.
Thus, while I agree with the majority’s conclusion on obviousness and anticipation and with much of the reasoning in Parts I and IV of the opinion, I part company with my colleagues in their unnecessary, and in my view improper, reference to the claims of the prior art patents.

. See Trial Tr. 647, Jun. 2, 2008 (Attorney Pope testifying that the EPO submissions were "redundant of information already before the examiner” because "[t]hat quote appears precisely in the '382 patent”), 653 ("[T]hey paraphrased the quote that they use, and in so doing, they picked up the language 'preferable.' That was, in my mind, simply because they were tracking the quote... .”); 677 ("I understand they used the word 'preferred' in their argumentation because they were simply tracking and paraphrasing the quote that they were discussing.”).

. See Trial Tr. 676 (Attorney Pope testifying that the '382/'636 patent “doesn’t give any reason why it says ‘preferably when being used on live blood,' whereas, when we look down to the sentence [in the EPO submission], they give a reason why you want the protective membrane.”).

. See Trial Tr. 647 (Attorney Pope testifying that "[t]he decision at the [EPO] Technical Board of Appeals was entirely consistent with my understanding at the time” that "preferably” meant "required”).

. See Trial Tr. 674 (Attorney Pope testifying: "The protective membrane was definitely optional. It depended—the option depended on what was being analyzed.”).

. See Trial Tr. 690 (Attorney Pope testifying: "My understanding was it was optional for any fluid other than blood.”); Trial Opinion, 565 F.Supp.2d at 1100 (Abbott's Proposed Finding No. 90: “the 'preferably' language means that the membrane is optional when an in vivo sensor does not contact whole blood but that the membrane is required when the sensor contacts red blood cells [i.e., erythrocytes] in whole blood.”).

. See Trial Tr. 661-62 (Attorney Pope testifying that "the claims encompassed a sensor that could be used on a variety of analytes. So the claim scope didn't speak to th[e] issue” of whether a membraneless sensor could be used in blood).

. The full paragraph of the EPO submission dated May 23, 1995 reads:
It is submitted that this disclosure is unequivocally clear. The protective membrane is optional, however, it is preferred when used on live blood in order to prevent the larger constituents of the blood, in particular erythrocytes from interfering with the electrode sensor. Furthermore it is said, that said protective membrane should not prevent the glucose molecules from *1316penetration, the membrane is "permeable” to glucose molecules. This teaches the skilled artisan that, whereas the semipermeable membrane of Dl must be constructed, for example by crosslinking, in such a way that the membrane will in fact control the permeability of the glucose at the required low value, the purpose of the protective membrane in the patent in suit is not to control the permeation of the glucose molecules. For this very reason the sensor electrode as claimed does not have (and must not have) a semipermeable membrane in the sense of Dl. The fact that the same material (cellulose acetate) may be used both for the semipermeable membrane of Dl and the protective membrane of the patent in suit is not relevant. The decisive feature is the modification (crosslinking) of said material to an extent so as to control the permeation of the substrate glucose. Finding the semipermeable membranes satisfying the requirements set forth on page 3, lines 24 to 56 of Dl is tedious and involves considerable trial and error work. Reproducability [sic] of such membranes is always a critical factor.
J.A. 6585-86 (emphases in original).

. See Trial Tr. 672 (Attorney Pope testifying that the "unequivocally clear” statement is directed to "the nature of the membrane ”; "And in my understanding, I believed that the reason the entire quote appears [in the EPO submission] is that is the only clear disclosure in the '382 patent or the '636 patent with regard to the nature of the protective membrane "There isn’t another sentence, another clear disclosure in the '636 patent that talks about the nature of the protective membrane." (emphases added)).

. See Trial Tr. 658 (Attorney Pope testifying: "I would disagree with the fact that the mere use of the word 'furthermore' means that it’s a second argument,” rather than "simply being a transitional word.”).

. See Pl.-Appellants’ Reply Br. 13 (“Thus, by showing that the '382/'636 did not use a membrane for at least some fluid, MediSense proved that it did not use the Dl’s glucose-controlling membranes.”).

. Hartzel v. United States, 322 U.S. 680, 686, 64 S.Ct. 1233, 88 L.Ed. 1534 (1944); United States v. Philip Morris USA Inc., 566 F.3d 1095, 1118 (D.C.Cir.2009); Pierre v. Attorney Gen., 528 F.3d 180, 189 (3d Cir.2008); United States v. Nguyen, 493 F.3d 613, 624 (5th Cir.2007); United States v. Zunie, 444 F.3d 1230, 1234 (10th Cir.2006); United States v. Puckett, 405 F.3d 589, 596 (7th Cir.2005); United States v. George, 386 F.3d 383, 390 (2d Cir.2004); United States v. De Leon, 270 F.3d 90, 92 (1st Cir.2001); United States v. Gracidas-Ulibarry, 231 F.3d 1188, 1196 (9th Cir.2000).

. The majority states that the district court found the individuals' explanations “so incredible that they suggested intent to deceive.” Maj. Op. 1306. A review of the district court’s opinion reveals no such finding.

. By assessing the “plausibility" or “credibility” of an individual's good faith explanation in light of the objectively defined materiality of the withheld information, the majority has, either wittingly or not, tied all three of the Ferring factors to a prior finding of materiality. See Praxair, 543 F.3d at 1313-14 (permitting an inference of deceptive intent to be drawn “when (1) highly material information is withheld; (2) ‘the applicant knew of the information [and] ... knew or should have known of the materiality of the information; and (3) the applicant has not provided a credible explanation for the withholding.’ ” (quoting Ferring B.V. v. Barr Labs., Inc., 437 F.3d 1181, 1191 (Fed.Cir.2006) (emphases added))).