Earlier this year, the Supreme Court finally resolved an issue that divided the U.S. Court of Appeals for the Federal Circuit (CAFC) for nearly 20 years. In Teva Pharm. USA, Inc. v. Sandoz, Inc., 135 S. Ct. 831, the Supreme Court unanimously held that a trial court’s underlying factual determinations with respect to extrinsic evidence used in patent claim constructions must be reviewed on appeal under the clearly erroneous standard rather thande novo.1

Before the Supreme Court’s decision in Teva, the CAFC reviewed patent claim constructionsde novo, including any allegedly fact-based questions relating to the trial court’s claim construction. As a result, it was quite common for the CAFC to reverse a trial court’s claim construction well after the completion of a lengthy jury trial. The case would be remanded to the trial court (unless the CAFC determined that the error would not have affected the judgment), in some instances leading to an entirely new trial on the merits (and, perhaps, another appeal to the CAFC). After Teva, many hope that CAFC claim construction reversals will be less frequent, particularly when litigants are able to introduce extrinsic evidence such as expert witness testimony into the claim construction process.

The CAFC has now had an opportunity to reconsider on remand not only its decision in Teva, but also Lighting Ballast Control LLC v. Philips Electronics N.A. Corp. which the Supreme Court also remanded to the CAFC for reconsideration in light of Teva.

In Teva, the CAFC held firm and once again reversed the trial court’s claim construction. InLighting Ballast, on the other hand, the CAFC changed course and affirmed the trial court’s claim construction, arguably giving more deference to the trial court’s decision than mandated by the Supreme Court. These two decisions, by different panels at the CAFC, demonstrate that though the issue of whether deference should be given to the trial court’s underlying factual findings has been resolved, the new challenge may be determining what is and is not a factual finding by the trial court.

In Part I we look at how the CAFC dealt with Teva on remand. In Part II (coming soon) we will examine the decision on remand in Lighting Ballast.

Patent claim construction2 and appellate review

The scope of a patent is defined by its claims, and construing and construing the meaning of patent claims is a question of law for the court — not a jury — to decide. Markman v. Westview Instruments, Inc., 517 U.S. 370, 390-91 (1996). Claim terms are given their ordinary and customary meaning to a person of ordinary skill in the relevant art, interpreted in the context of the patent as a whole. A court will also considers the prosecution history of the patent, with the claims, specification and prosecution history referred to as the “intrinsic evidence.” In some instances (but not all) a court will consider “extrinsic evidence” — evidence outside of the patent itself — if the court believes such evidence will aid in the claim construction. This extrinsic evidence typically includes things such as dictionaries, treatises and expert witness testimony.

Because patent claim construction is a question of law, the appellate court conducts a de novoreview of the construction of a claim, without giving deference to the trial court. Claim constructions are sometimes based, in part, on underlying factual findings by the trial court, such as determining the meaning of a technical term in the relevant art based on extrinsic evidence (e.g., expert testimony). Findings of fact, however, are normally reviewed on appeal under the clearly erroneous standard — the appellate court will not overturn the trial court’s factual determinations unless it has a “definite and firm conviction that a mistake has been committed.” United States v. United States Gypsum Co., 333 U.S. 364, 395 (1948). Nevertheless, prior to the Supreme Court’s decision in Teva, the CAFC reviewed patent claim constructions de novo, including any allegedly fact-based questions relating to the trial court’s claim construction.

In Teva Pharmaceuticals USA, Inc. v. Sandoz Inc., the Supreme Court held that though the CAFC must continue to review de novo a trial court’s ultimate interpretation of the patent claims, any underlying factual findings of the trial court must be reviewed using the clearly erroneous standard. The Supreme Court also established a clear delineation between a trial court’s evaluation of intrinsic and extrinsic evidence. “[W]hen the district court reviews only evidence intrinsic to the patent (the patent claims and specifications, along with the patent’s prosecution history), the judge’s determination will amount solely to a determination of law, and the court of appeals will review that construction de novo.” 135 S. Ct. 831, 841. However, when the trial court must “consult extrinsic evidence in order to understand, for example, the background science or the meaning of a term in the relevant art during the relevant time period,” such “subsidiary factfinding[s] must be reviewed for clear error on appeal.” Id.

The court reiterated, however, that there remains a clear distinction between subsidiary findings of fact, reviewed for clear error, and the ultimate legal construction of a claim term that must be reviewed de novo on appeal. “[E]xperts may be examined to explain terms of art, and the state of the art, at any given time, but they cannot be used to prove the proper or legal construction of any instrument of writing.” Id. Thus, though “in some instances, a factual finding may be close to dispositive of the ultimate legal question of the proper meaning of the term in the context of the patent,…the ultimate question of construction will remain a legal question.” Id. at 841-42.

Teva on remand

The claims at issue in Teva were directed to a particular polymer having a “molecular weight of about 5 to 9 kilodaltons.” All parties agreed that the claim term “molecular weight” of a polymer has no generally accepted meaning in the art, as it can refer to Mp, Mn or Mw.3Thus, because the patent did not explicitly indicate which of these three possibilities “molecular weight” referred to, the accused infringers asserted that the claims were indefinite and therefore invalid. Based largely on the testimony of Teva’s expert witness, the trial court construed “molecular weight” in the claims to refer to the peak average molecular weight (Mp), and therefore held that the claims were not invalid as being indefinite.4

In its original decision, the CAFC reversed the finding of validity, disagreeing with the trial court’s construction of “molecular weight.” In doing so, the CAFC reviewed the trial court’s claim construction de novo, without giving any deference to the trial court even with respect to underlying factual determinations. The Supreme Court vacated the original CAFC decision and remanded the case for further consideration.

On remand from the Supreme Court, a 2-1 panel majority of the CAFC held fast to its earlier decision, once again reversing the trial court. In doing so, the majority went to great lengths to explain that every identified fact finding by the trial court related to claim construction was not “clearly erroneous.” Nevertheless, reviewing the ultimate question of the meaning of “molecular weight” de novo, the CAFC held, as a matter of law, that the claims were indefinite and therefore invalid.5

The majority first noted that, as instructed by the Supreme Court, “[e]xperts may explain terms of art and the state of the art at any given time, but they cannot be used to prove the legal construction of a writing.” 2015 U.S. App. LEXIS 10229, *8. The majority went on to identify several subsidiary factual findings made by the trial court, all of which the majority determined were not clearly erroneous:

  1. Mp is the only molecular weight that can be directly obtained from the analytical method described in Example 1 of the patent (Mn and Mw can only be obtained after additional data manipulation and calculations not disclosed in the patent).
  2. Figure 1 in the patent was created by transforming data acquired from the analytical method described in Example 1.
  3. A person of ordinary skill would understand that the process of transforming such data could cause the peaks of each curve in Fig. 1 to shift slightly, such that the “average molecular weights” in Fig. 1 fall approximately at the peaks of the curves depicted in Fig. 1 (i.e., Mp).

However, the panel majority stopped there, stating that accepting these factual findings did not create a “presumption” that, as used in the claims, “molecular weight” meant Mp. Id. at *15. A district court should not defer to an expert’s ultimate conclusion about claim meaning in the context of the patent, and the CAFC should not defer to the district court on this question of law. Id. at *15-16.

The above factual findings, which the CAFC found to be not clearly erroneous, might ordinarily have been sufficient for the CAFC to affirm the trial court’s interpretation of “molecular weight” even under the de novo standard of review. However, as the panel majority pointed out, the prosecution history (part of the intrinsic evidence) is also relevant to claim construction and the legal question of whether one skilled in the art would be “reasonably certain that the claim’s use of molecular weight is Mp.” The prosecution history was very problematic for Teva.

During prosecution of two related Teva patents (having specifications identical to the patent in question), the examiner initially rejected the claims as being indefinite with respect to the meaning of “average molecular weight.” In the first related patent (the ‘847 patent), Teva obtained allowance of the patent by arguing that “[o]ne of ordinary skill in the art could understand that kilodalton units implies a weight average molecular weight” (i.e., Mw). Id. at *19. In the second (the ‘539 patent), Teva changed course and successfully argued that “a person of ordinary skill in the art, upon reviewing the specification, would understand that ’average molecular weight’ refers to the molecular weight at the peak of the molecular distribution curve in Figure 1” (i.e., Mp). Id. at *22. The trial court dealt with these contradictory statements by concluding that based upon the testimony of Teva’s expert, the statement during prosecution of the ‘847 patent that molecular weight meant Mw was based on a “scientifically erroneous” argument.[6] Therefore, one skilled in the art would have relied on the statement during prosecution of the ‘539 patent that “molecular weight” referred to Mp.

The CAFC majority, though giving deference to the trial court’s fact finding that the statement made during prosecution of the ‘847 patent was “scientifically erroneous,” held that determining the significance of the prosecution statements with respect to claim construction was a question of law, and therefore reviewed de novo. As a result, the majority reached the legal conclusion that despite the subsidiary factual findings by the trial court, when viewed in light of the specification and prosecution history of the related patents, the patentee failed to inform with reasonable certainty those skilled in the art as to the meaning of “molecular weight.” Thus, the claim in question was held invalid for indefiniteness.

Judge Mayer, in dissent, argued that “the district court made a factual finding that an artisan skilled in the art of polypeptide synthesis would have inferred from the use of an analytic technique known as size exclusion chromatography (SEC) in [the patent in suit] that the term ‘molecular weight’ referred to peak average molecular weight.” Id. at *25. Judge Mayer further argued that the trial court also made a factual determination that “a person of ordinary skill in the art would have accepted a statement made by the patentee during prosecution of [the ‘539 patent] as ‘proof’ of what was meant by the term ‘molecular weight’.”Id. Because neither of these factual findings was clearly erroneous, Judge Mayer would have affirmed the trial court’s conclusion that the claim was not invalid for indefiniteness.

Though the Supreme Court in Teva stated that “in some instances, a factual finding may be close to dispositive of the ultimate legal question of the proper meaning of the term in the context of the patent,” Judge Mayer may have taken this statement too far. Indeed, the trial court’s determination that one skilled in the art would have inferred from the specification that the term “molecular weight” referred to Mp would appear to be a determination of the ultimate legal question of the meaning of “molecular weight” — not a “factual finding,” as Judge Mayer argues.

As the Supreme Court noted, for example, the trial court made a factual finding that the process of transforming certain data could cause shifts in the peaks of each curve in Fig. 1 to shift slightly. But the court went on to state that applying this factual finding to the context of the patent was a legal determination: “Based on that factual finding, the District Court reached the legal conclusion that figure 1 did not undermine Teva’s argument that molecular weight referred to the first method of calculation (peak average molecular weight).” 135 S. Ct. 831, 843 (emphasis added).

Furthermore, Judge Mayer appears to have gone too far when he asserted that the trial court made a factual determination that one skilled in the art would have accepted the statement made during prosecution of the ‘539 patent as “proof of what was meant by the term ‘molecular weight,”[7] while apparently ignoring the contrary statement made during prosecution of the ‘847 Patent. As the Supreme Court noted:

[I]f a district court resolves a dispute between experts and makes a factual finding that, in general, a certain term of art had a particular meaning to a person of ordinary skill in the art at the time of the invention, the district court must then conduct a legal analysis: whether a skilled artisan would ascribe that same meaning to that term in the context of the specific patent claim under review. That is because “[e]xperts may be examined to explain terms of art, and the state of the art, at any given time,” but they cannot be used to prove “the proper or legal construction of any instrument of writing.”Winans v. New York & Erie R. Co., 21 How. 88, 100–101 (1859).

135 S. Ct. 831, 841 (emphasis added). The prosecution history is part of the intrinsic evidence for patent claim construction — it is part of the “context of the specific patent claim.” Whether one skilled in the art would accept the second prosecution argument as “proof” of the meaning of a claim term while ignoring a contrary prosecution argument is not, in my opinion, a factual determination to be reviewed under the clearly erroneous standard on appeal. Claim terms cannot be redefined during prosecution. Therefore, it would seem that the argument made during prosecution of the ‘539 patent is no different than an expert witness opining that a person of ordinary skill in the art, upon reviewing the specification, would understand that “average molecular weight” refers to Mp. As such, it is not “proof” of the meaning of “molecular weight.” Rather, it is, at most, an expert’s opinion on the ultimate legal question of the meaning of a claim term, and therefore entitled to no deference on appeal.

As the split decision in Teva on remand demonstrates, applying the Supreme Court’s decision may not be as straightforward as it seems. Judge Mayer was willing to extend the clearly erroneous standard of review further than the other panel members, apparently even so far as the ultimate legal conclusion of the meaning of a claim term. As we will see in Part II, the CAFC panel in Lighting Ballast appears to taken an approach similar that of Judge Mayer, deferring to the trial court on every claim construction determination. This suggests that Tevamay have a more significant effect on appellate review than many expected.