Siemens Medical Solutions v. Saint-Gobain Ceramics & Plastics (CAFC 2010-1145, 1177) precedential

Although '080 was the only asserted patent, two others were involved: 6,624,420 and 6,323,489. '420, licensed to Saint-Gobain, claims a similar technology to '080, citing '080 as prior art. '489 and '420 had an interference spat. So, these three patents are in the same neighborhood.

Saint-Gobain filed a post-trial motion for JMOL or a new trial, in which Saint-Gobain challenged the following decisions of the district court: (1) a decision not to instruct the jury that infringement by equivalence must be proved in this case by clear and convincing evidence; (2) a decision not to instruct the jury that the '420 patent is presumed valid; (3) a decision not to admit into evidence the '489 patent and certain expert testimony; and (4) a decision to permit the jury to consider lost profits damages. Saint-Gobain further argued that the court should remit the jury's damages award.

In its opinion and order dated May 15, 2009, the district court denied Saint-Gobain's post-trial motion for JMOL or for a new trial. JMOL Opinion at 320. However, the court granted Saint-Gobain's request to reduce the jury's damages award, finding that evidence supported the jury verdict only up to $44,937,545. Id. at 319.

The district court lowered the number of infringing scanners sold prior to '080's expiration, thus reducing the award.

Saint-Gobain appeals the district court's denial of its motion for JMOL or for a new trial. In particular, SaintGobain challenges the district court's jury instructions with regard to the doctrine of equivalents and the presumption of validity, the decision of the district court to exclude certain evidence, and the district court's decision to permit the jury to consider lost profits damages. Siemens cross-appeals the district court's reduction of the jury's damages award.

A. Jury Instructions

1. Burden of Proof for Infringement under the Doctrine of Equivalents

Heightened burden of proof has become a popular cry for losers. Loser Microsoft (v. i4i) has that going for invalidity all the way to the Supreme Court, which always toadies to power, governmental or corporate.

Saint-Gobain argues that the district court legally erred in its jury instructions regarding proof of infringement under the doctrine of equivalents. Saint-Gobain asserts that, in cases where an alleged equivalent is separately patented, a heightened evidentiary burden is required.

The doctrine of equivalents prohibits one from avoiding infringement liability by making only "insubstantial changes and substitutions . . . which, though adding nothing, would be enough to take the copied matter outside the claim, and hence outside the reach of law." Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 607 (1950). The "essential inquiry" in any determination under the equivalents doctrine is whether "the accused product or process contain[s] elements identical or equivalent to each claimed element of the patented invention." Warner-Jenkinson Co., Inc. v. Hilton Davis Chem. Co., 520 U.S. 17, 40 (1997). We have assessed the insubstantiality of an alleged equivalent by applying the function-way-result test as set forth in Union Paper-Bag Mach. Co. v. Murphy, 97 U.S. 120, 125 (1877), which asks whether an element of an accused product "performs substantially the same function in substantially the same way to obtain the same result" as an element of the patented invention. See, e.g., TIP Sys., LLC v. Phillips & Brooks/Gladwin, Inc., 529 F.3d 1364, 1376 (Fed. Cir. 2008); Abraxis Biosci., Inc. v. Mayne Pharma (USA) Inc., 467 F.3d 1370, 1379 (Fed. Cir. 2006); see also Graver Tank, 339 U.S. at 608. We remain mindful, however, that "'[e]quivalence, in the patent law, is not the prisoner of a formula and is not an absolute to be considered in a vacuum.'" Warner-Jenkinson, 520 U.S. at 24-25 (quoting Graver Tank, 339 U.S. at 609).

Rule of law is a flexible veneer. Note the weasel words about not being a prisoner to formula, as in, consistency is the hobgoblin of small-minded judges. In this case, however, the formula holds 2-1.

Saint-Gobain makes an interesting argument, not illogical, (and ably articulated by the dissent) regarding a correspondence between the nonobviousness of an accused product, as shown by its separate patentability, and its infringement of another patent under the doctrine of equivalents. However, we agree with Siemens that the district court did not legally err by instructing the jury that infringement in this case may be proved by a preponderance of the evidence. Patent infringement, whether literal or by equivalence, is an issue of fact, which the patentee must prove by a preponderance of the evidence. Cross Med. Prods., Inc. v. Medtronic Sofamor Danek, Inc., 424 F.3d 1293, 1310 (Fed. Cir. 2005) ("To prove direct infringement, the plaintiff must establish by a preponderance of the evidence that one or more claims of the patent read on the accused device literally or under the doctrine of equivalents."); see also Morton Int'l, Inc. v. Cardinal Chem. Co., 5 F.3d 1464, 1468 (Fed. Cir. 1993); SRI Int'l v. Matsushita Elec. Corp. of Am., 775 F.2d 1107, 1123 (Fed. Cir. 1985) (en banc) ("The patentee bears the burden of proving infringement by a preponderance of the evidence.").

The issue of infringement by a separately patented equivalent was addressed in the Supreme Court decision of Sanitary Refrigerator Co. v. Winters, 280 U.S. 30 (1929). In that case, the patent in suit, filed by Winters and Crampton, claimed an improved refrigerator door latch that automatically locked as the door closed. Id. at 36-37. The allegedly infringing door latch was covered by a later-issued U.S. patent to Schrader. In its opinion, the Court first acknowledged that the accused device did not literally infringe the narrow claims of the Winters and Crampton patent. Id. at 41. The Court then proceeded to apply the function-way-result test to the accused device and found infringement by equivalence. Id. at 41-42. The Court held that infringement cannot be avoided in a device that has "no substantial departure" from the claimed invention. Id. at 42. The Court further noted: "Nor is the infringement avoided . . . by any presumptive validity that may attach to the Schrader patent by reason of its issuance after the Winters and Crampton patent." Id. at 43. The Court thus found equivalence in the face of separate patentability without imposing a heightened evidentiary burden.

The passage in Festo relied on by Saint-Gobain includes citations of numerous cases in which we, like the Court in Sanitary Refrigerator, rejected arguments that separate patentability warrants anything more than consideration of this fact together with all others weighing for and against equivalency. Festo, 493 F.3d at 1379 n.8 (citing Glaxo Wellcome, Inc. v. Andrx Pharms., Inc., 344 F.3d 1226 (Fed. Cir. 2003); Hoechst Celanese, 78 F.3d 1575; Nat'l Presto Indus. v. W. Bend Co., 76 F.3d 1185 (Fed. Cir. 1996); Atlas Powder Co. v. E.I. du Pont De Nemours & Co., 750 F.2d 1569 (Fed. Cir. 1984)).

None of these cases cited in Festo supports a requirement of proof of equivalency by clear and convincing evidence in cases involving separate patentability. Indeed, in other cases we have likewise indicated that separate patentability, while potentially relevant to the equivalence issue and deserving of due weight in the infringement analysis, does not merit a heightened evidentiary burden. See, e.g., Abraxis Biosci., 467 F.3d 1370, 1382 (Fed. Cir. 2006) (affirming the district court's finding of infringement by equivalence and stating that separate patentability of the accused pharmaceutical formulation did not outweigh substantial evidence of its equivalence); Fiskars, Inc. v. Hunt Mfg. Co., 221 F.3d at 1324 (holding that the trial court judge did not err by withholding evidence of separate patentability from the jury, because "it is well established that separate patentability does not avoid equivalency as a matter of law"); Zygo Corp. v. Wyko Corp., 79 F.3d 1563, 1570 (Fed. Cir. 1996) ("The nonobviousness of the accused device, evidenced by the grant of a United States patent, is relevant to the issue of whether the change therein is substantial.").

Saint-Gobain tried to handcuff infringement equivalence to invalidity obviousness. The majority didn't bite, but there was a well-reasoned dissent going the other way.

Moreover, with regard to Saint-Gobain's contention that equivalence is tantamount to obviousness, we disagree. The two legal principles require different analytical frameworks. The doctrine of equivalents, although "not the prisoner of a formula," Graver Tank, 339 U.S. at 609, typically involves application of the insubstantial differences test, usually via the function-way-result test. Obviousness, by contrast, requires analysis under the four Graham factors. Graham v. John Deere Co., 383 U.S. 1, 17-18 (1966); accord KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398, 406-07 (2007). Unlike equivalence, an obviousness inquiry may center on, for example, objective evidence of commercial success, e.g., Symbol Techs., Inc. v. Opticon, Inc., 935 F.2d 1569, 1579 (Fed. Cir. 1991), or on the level of predictability in the art, e.g., SanofiSynthelabo v. Apotex, Inc., 550 F.3d 1075, 1089 (Fed. Cir. 2008). Indeed, although we express no view regarding the validity of the '420 patent, we note that Saint-Gobain's "constructive invalidity" argument fails to account for the commercial success of its own 10% Y LYSO crystals or the unpredictability in the field of crystallization. See, e.g., id. (noting experts' agreement regarding the unpredictability of crystallization).

Furthermore, the time frames of the two inquiries differ. Under the doctrine of equivalents, "the proper time for evaluating equivalency . . . is at the time of infringement, not at the time the patent was issued," Warner-Jenkinson, 520 U.S. at 37, yet obviousness asks whether a claimed invention "would have been obvious at the time the invention was made," 35 U.S.C. § 103(a). These and other differences between equivalence and obviousness undermine Saint-Gobain's theory of "constructive invalidation."

Saint-Gobain's professed justification for a clear and convincing standard also overlooks an important distinction regarding claim scope.

In summary, we agree with neither the proposed rule nor the rationale proffered by Saint-Gobain. We, like the district court, "decline[] to be the first (and only) court to depart from an extended history of patent infringement jurisprudence applying the preponderance of the evidence standard." JMOL Opinion at 310. We therefore hold that, even though the alleged equivalent in this case was separately patented, the district court did not legally err by instructing the jury that infringement under the doctrine of equivalents may be proved by a preponderance of the evidence.

2. Presumption of Validity

Saint-Gobain had another hogwash argument about jury instructions, that the jury was not informed that a patent was entitled to a presumption of validity.

We conclude that the district court's decision not to provide separate instructions to the jury about the presumption of validity did not "clearly mislead the jury." DSU Med., 471 F.3d at 1304 (internal quotation marks omitted). Patent validity was not an issue before the jury: the validity of the '080 patent was not challenged at trial, and, as we explained above, the verdict of infringement by equivalence in no way affected the validity of the '420 patent. As the district court correctly noted, Siemens probed aspects of the '420 patent in connection with Saint-Gobain's license defense to willfulness, but "appropriately stopped short of directly challenging the validity of the '420 patent." JMOL Opinion at 313. Thus, the requested instruction was not directly relevant to the issues before the jury.

B. Exclusion of Evidence

We review a district court's decision to exclude evidence under the law of the regional circuit. Del. Valley Floral Grp., Inc. v. Shaw Rose Nets, LLC, 597 F.3d 1374, 1379 (Fed. Cir. 2010). The Third Circuit reviews a district court's decision to exclude evidence for abuse of discretion. Glass v. Phila. Elec. Co., 34 F.3d 188, 191 (3d Cir. 1994); see also Rhodia Chimie v. PPG Indus., Inc., 402 F.3d 1371, 1376-77 (Fed. Cir. 2005). "A ruling excluding evidence under Rule 403 is accorded particular deference, and . . . it may not be reversed unless the determination is arbitrary and irrational." In re Paoli R.R. Yard PCB Litig., 113 F.3d 444, 453 (3d Cir. 1997) (internal quotation marks omitted). An erroneous evidentiary ruling "is harmless only if it is highly probable that the error did not affect the outcome of the case." Glass, 34 F.3d at 191 (internal quotation marks omitted).

Saint-Gobain had specious arguments "that the district court erred by excluding the '489 patent from evidence." The CAFC found that Saint-Gobain had not teed up the argument it presented on appeal until after trial, effectively waiving it, and "that any error associated with the district court's ruling was harmless."

Saint-Gobain had similar lack of luck about a portion of its expert (Dr. McClellan) testimony excluded.

The court's evidentiary ruling was justified and well reasoned. The court's judgment comports with Fed. R. Civ. P. 26(a)(2)(B)(i)-(ii), which requires experts to provide a written report containing "a complete statement of all opinions the witness will express and the basis and reasons for them" and "the facts or data considered by the witness in forming them." As the Advisory Committee Note accompanying the 1993 amendments to Rule 26 explains: "Given this obligation of disclosure, litigants should no longer be able to argue that materials furnished to their experts to be used in forming their opinions-- whether or not ultimately relied upon by the expert--are privileged or otherwise protected from disclosure when such persons are testifying or being deposed." Fed. R. Civ. P. 26 advisory committee's note.

Rule 26, therefore, "proceeds on the assumption that fundamental fairness requires disclosure of all information supplied to a testifying expert in connection with his testimony." In re Pioneer Hi-Bred Int'l, Inc., 238 F.3d 1370, 1375 (Fed. Cir. 2001). We agree with the district court that "the fundamental principle of fairness" supports its sensible limitations on Dr. McClellan's testimony, as Siemens had "no principled way to test his recollection and opinion." Evidence Order at *1.

The court's ruling further complies with Fed. R. Civ. P. 37(c)(1), which states that, if a party fails to comply with Rule 26(a), "the party is not allowed to use that information or witness to supply evidence on a motion, at a hearing, or at a trial, unless the failure was substantially justified or is harmless." Saint-Gobain does not argue that its failure to disclose was substantially justified or harmless. Thus, the district court did not abuse its discretion by ruling that Dr. McClellan could not testify on matters not disclosed in his expert report or deposition, and that he could not rely on testing that was not disclosed to Siemens during discovery.

C. Lost Profits Damages

Whether lost profits are legally compensable in a particular situation is a question of law that we review de novo. Poly-Am., L.P. v. GSE Lining Tech., Inc., 383 F.3d 1303, 1311 (Fed. Cir. 2004) (citing Rite-Hite Corp. v. Kelley Co., 56 F.3d 1538, 1544 (Fed. Cir. 1995) (en banc)). "To recover lost profits, the patent owner must show causation in fact, establishing that but for the infringement, he would have made additional profits." Wechsler v. Macke Int'l Trade, Inc., 486 F.3d 1286, 1293 (Fed. Cir. 2007) (internal quotation marks omitted). Thus, in general, "the patent owner must prove (1) a demand for the patented product, (2) an absence of acceptable noninfringing substitutes, (3) the manufacturing and marketing capability to exploit the demand, and (4) the amount of profit the patent owner would have made." Cohesive Techs., Inc. v. Waters Corp., 543 F.3d 1351, 1373 (Fed. Cir. 2008) (quoting Standard Havens Prods., Inc. v. Gencor Indus., Inc., 953 F.2d 1360, 1373 (Fed. Cir. 1991)); see also Panduit Corp. v. Stahlin Bros. Fibre Works, Inc., 575 F.2d 1152, 1156 (6th Cir. 1978).

The pot calling the kettle black, Saint-Gobain argued that Siemens had not provided sufficient evidence. That got waved away. One argument over proper calculation of lost profits revolved around a third competitor, GE.

We perceive no legal error in the district court's decision to permit the jury to award lost profits damages. On appeal, the dispute between Saint-Gobain and Siemens over lost profits centers on (1) whether there existed a two-supplier, high-end market for PET scanners, and (2) whether LaBr3 scanners were available, acceptable noninfringing alternatives to LSO scanners. On both issues, Siemens presented substantial evidence to support a lost profits award.

Accurately identifying a two-supplier market "'requires an analysis which excludes alternatives to the patented product with disparately different prices or significantly different characteristics.'" Micro Chem., Inc. v. Lextron, Inc., 318 F.3d 1119, 1124 (Fed. Cir. 2003) (quoting Crystal Semiconductor Corp. v. TriTech Microelecs. Int'l, Inc., 246 F.3d 1336, 1356 (Fed. Cir. 2001)). Here, the parties disputed whether GE's BGO scanner was an alternative to the LSO and LYSO scanners such that a three-supplier market existed. The district court summarized the ample evidence that BGO was generally inferior to LSO with respect to important scintillator properties, including light output and decay time. JMOL Opinion at 315-16. In addition, the district court credited the testimony of Siemens' head of marketing and sales, who testified that BGO-based scanners do not compete with Siemens' LSO-based scanners in the high-end PET scanner market, id. at 316, because BGO scanners, with their relatively poor image quality, were purchased by "customers that are extremely tight in their budgets," whereas the more expensive LSO scanners were purchased by customers seeking the "highest performance and high technology." J.A. 985.

The district court also credited Saint-Gobain's own documents and the testimony of Saint-Gobain's witnesses, which consistently described a two-supplier "high-end PET scanner market" consisting only of LSO and LYSO scanners. JMOL Opinion at 316. Saint-Gobain is correct in arguing that its damages expert provided testimony indicating that Siemens lost some sales to GE's BGO scanners during the relevant time period. However, as the district court correctly noted, there was ample evidence for a reasonable jury to infer the existence of a twosupplier market for high-end PET scanners consisting of Siemens' LSO scanners and Philips' LYSO scanners. Id.

Another lost cause for Saint-Gobain.

D. Cross-Appeal of the Reduction of the Jury's Damage Award

The dispute here centered over the sales status of 18 scanners.

Here, the jury determined that Saint-Gobain infringed the '080 patent by inducing and contributing to Philips' infringement. JMOL Opinion at 309. The district court correctly noted that substantial evidence supported the conclusion that Philips made the additional 18 scanners. Id. at 319. One who "makes" a patented invention without authorization infringes the patent. 35 U.S.C. § 271(a) (2006). Yet, after eliminating the jury's lost profits award on these 18 scanners, the district court failed to consider whether any "damages adequate to compensate for the infringement" were owed to Siemens. 35 U.S.C. § 284 (2006); see also JMOL Opinion at 319. If district court eliminates a lost profits award with regard to a portion of infringing devices, the court must then determine an appropriate measure of damages for that portion. Crystal Semiconductor, 246 F.3d at 1355. Overlooking the requirement of 35 U.S.C. § 284 is legal error. Id.

Here, the court abused its discretion by failing to determine a reasonable royalty for the remaining 18 scanners.

We therefore remand to the district court so that the court may determine a reasonable royalty for the additional 18 scanners, to be added to the award of $44,937,545 in lost profits for 61 scanners that were sold. In determining the reasonable royalty, the district court may rely on the present record if deemed adequate, or may elect to receive additional expert testimony on what royalty would be reasonable under the circumstances. 35 U.S.C. § 284 (2006).

Siemens scores. Again.

The district court's judgment entered in favor of Siemens is affirmed. However, we vacate the damages award and remand for the court to consider a reasonable royalty for the additional 18 infringing scanners, to be added to the $44,937,545 in lost profits for the 61 scanners that were sold.

Judge Lourie penned the majority opinion, with Judge Linn along.

A tense Judge Prost dissented with spry reasoning.

There is a tension between the equivalence and nonobviousness inquiries presented in this appeal.

As it has here, this tension comes to light when a patentee asserts the doctrine of equivalents against some feature that the U.S. Patent and Trademark Office ("PTO") declared to be a point of novelty in a separate patent. To prevail on equivalence, the patentee must prove that the feature is insubstantially different from the limitations of his asserted claim. Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 610 (1950); accord Chiuminatta Concrete Concepts, Inc. v. Cardinal Indus., Inc., 145 F.3d 1303, 1310 (Fed. Cir. 1998). In an ordinary case, we would say that the patentee's efforts to prove infringement will not be hindered by an accused infringer's proof of separate patenting. Atlas Powder Co. v. E.I. du Pont De Nemours & Co., 750 F.2d 1569, 1581 (Fed. Cir. 1984). The equivalence analysis, however, presents a unique circumstance.

Where equivalence is used against a feature that is separately patented, the patentee's attempts to show that the feature is insubstantially different from the asserted patent crash into the well-settled presumption that patents are nonobvious over the prior art. See Zygo Corp. v. Wyko Corp., 79 F.3d 1563, 1570 (Fed. Cir. 1996). When a fact finder concludes that a feature is "insubstantially different" from a patent, how are we then to view the validity of the patent putatively establishing that same feature as "nonobvious"?

Examining the legal standards underlying obviousness and equivalence only emphasizes the potential for overlap. The Supreme Court has instructed us that four factors should be used in assessing obviousness: (1) the scope and content of the prior art, (2) the differences between the prior art and the claims, (3) the level of ordinary skill in the art, and (4) secondary considerations such as commercial success, unexpected results, and longfelt need. Graham v. John Deere Co. of Kan. City, 383 U.S. 1, 17-18 (1966); accord Syntex (U.S.A.) LLC v. Apotex, Inc., 407 F.3d 1371, 1378 (Fed. Cir. 2005). These factors are intended to guide judges and juries in determining whether a hypothetical "skilled artisan" would have viewed the claimed invention as one that was suggested in a straightforward way by the prior art and the general level of knowledge in the field. KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398, 417-18 (2007). The caselaw is replete with courts elaborating these standards in the hope of making this difficult analysis as fair and straightforward as possible.

The standard for equivalence--"insubstantial difference"--has also been well-explored. If a skilled artisan, at the time of the accused infringement, viewed a substitution to a patented invention as insubstantially different from the claim, the substitution is equivalent and infringement may arise. Graver Tank, 339 U.S. at 610; Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 40 (1997). The doctrine prevents accused infringers from evading liability by making "trivial" changes to the patented invention. Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 733 (2002). That a substitution is "trivial" or "insubstantially different" may be proved by showing that the substitution performs the same function, in the same way, with the same result as the technology of the claim limitation. Catalina Marketing Int'l, Inc. v. Coolsavings.com, Inc., 289 F.3d 801, 813 (Fed. Cir. 2002).

The majority reasons that these two tests, obviousness and equivalence, are separate from one another. But while the details differ, I find there is an inevitable area of overlap. Assume a court, applying Graver Tank and its progeny, found that to a person of skill in the art a substitution was insubstantially different from a claim limitation. Having so found, and setting aside (for the moment) consideration of the time frames at which obviousness and equivalence are assessed, the court would need only a further finding that the skilled artisan had some reason to make the substitution to find the limitation obvious under Graham and KSR.¹ This is not a high bar. For a truly insubstantial change, the predictability of outcome when substituting the one for the other suggests that a reason to combine will be easy to prove. Rothman v. Target Corp., 556 F.3d 1310, 1319 (Fed. Cir. 2009).

¹In the past, some litigants attempted to avoid this second step entirely, and prove "anticipation by equivalents." This court rejected that theory, holding that a claim is invalid under § 102 if and only if each and every limitation of the claim is literally present in a single prior art reference. But while it rejected "anticipation by equivalents," this court noted that the doctrine of equivalents was, "if one wished to draw a parallel, . . . somewhat akin to obviousness." Lewmar Marine, Inc. v. Barient, Inc., 827 F.2d 744, 748 (Fed. Cir. 1987); see also Richardson v. Suzuki Motor Co., 868 F.2d 1226, 1236 (Fed. Cir. 1989) (discussing the doctrine of equivalents as "a legal theory that is pertinent to obviousness under Section 103, not to anticipation under Section 102"). Notably, however, this court has declined to extend the doctrine of equivalents to cover on infringement embodiments that were present in the prior art. Wilson Sporting Goods Co. v. David Geoffrey & Assocs., 904 F.2d 677, 685 (Fed. Cir. 1990), overruled in part on other grounds by Cardinal Chem. Co. v. Morton Int'l, Inc., 508 U.S. 83, 99-103 (1993).

Judge Nies anticipated the challenge we face when she wrote, "a substitution in a patented invention cannot be both nonobvious and insubstantial." Roton Barrier, Inc. v. Stanley Works, 79 F.3d 1112, 1128 (Fed. Cir. 1996) (Nies, J., Additional Views). A similar concern was voiced by Judge Dyk (and quoted by the majority) in this court's Festo decision. Maj. Op. at 10 (quoting Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 493 F.3d 1368, 1379-80 (Fed. Cir. 2007)). This appeal now squarely presents the issue.

I believe that the best path through this difficult situation is to expressly incorporate Judges Nies and Dyk's reasoning into the equivalence analysis: a separately-patented (and presumptively nonobvious) substitution cannot be "insubstantial" unless some fact distinguishes the equivalence finding from the PTO's earlier nonobviousness determination.

The passage of time presents one opportunity for such a distinction. The majority is correct that an equivalence analysis differs from an obviousness analysis in the time frame concerned. Obviousness is assessed at the time of the invention, and equivalence at the time of the alleged infringement. A finding that, from the time of the separately-patented invention to the time of accused infringement, the state of the art advanced in such a way as to make a previously non-obvious substitution obvious, would allow an equivalence finding without upsetting the presumption of nonobviousness. In the absence of such a finding, in my view a separately-patented substitution may not be held equivalent.

I therefore disagree with the majority in that I do not view it acceptable to leave the fact-finder--here, a jury-- without instruction on how it might navigate the equivalence inquiry without undermining the presumption of nonobviousness that we must accord issued patents.