Claim Differentiation Can BE Overcome by the Written Description or Prosecution History

Regents of the University of California v. Dakocytomation California, Inc., [2006-1334, -1452] (February 28, 2008) [LOURIE, Mayer, Prost] The Federal Circuit concluded that the district court correctly construed the term "heterogeneous mixture of labeled unique sequence nucleic acid fragments," erred in its construction of "morphologically identifiable cell nucleus," and erred by concluding that appellants were barred by the doctrine of prosecution history estoppel, it affirmed in part, reversed in part, and remanded for further proceedings.

BRIEF: The district court interpreted "heterogeneous mixture of labeled unique sequence nucleic acid fragments" based upon its belief that the patentee's earlier patent was prior art, but then corrected its decision after plaintiff pointed out that the patent in suit was a divisional from the parent, the district court then adopted the same construction because otherwise the patent would be invalid for double patenting. Although this, too, was incorrect, because the patentee had filed a terminal disclaimer, the Federal Circuit still found that the district court's construction was correct. The Federal Circuit said the district court correctly evaluated the prosecution history and determined the proper claim construction, and agreed that the patentees disclaimed embodiments that include repetitive sequences during the prosecution of the patent.

The Federal Circuit said that it is a truism that the claims of a patent define the invention that is claimed, but the prosecution history can often inform the meaning of the claim language by demonstrating how the inventor understood the invention and whether the inventor limited the invention in the course of prosecution, making the claim scope narrower than it would otherwise be. The Federal Circuit noted that the language "unique sequence" was added during prosecution, and although the patentees did not expressly state whether the "unique sequence" limitation was added in response to any particular rejection, given the patentees’ arguments accompanying the amendment, as well as previous statements patentees made during the prosecution of the parent application, the term "unique sequence" was clearly added to overcome the enablement rejection. Noting that in the parent application the applicant said that embodiments involving the removal of repetitive sequences would be pursued in a separate application. The addition of "unique sequence" to the heterogeneous mixture limitation, coupled with the patentees’ statements during prosecution, evince a clear intent to limit the claims of the patent to those embodiments in which the repetitive sequences have been excluded from the heterogeneous mixture in order to disable the hybridization capacity of repetitive sequences. The patentee relied upon AK Steel Corp. v. Sollac and Ugine, for the proposition that "dependent claims are presumed to be of narrower scope than the independent claims from which they depend" under the doctrine of claim differentiation. The Federal Circuit found the argument unpersuasive, however, because presumptions are rebuttable. While it is true that dependent claims can aid in interpreting the scope of claims from which they depend, they are only an aid to interpretation and are not conclusive. The presumption created by the doctrine of claim differentiation is not a hard and fast rule and will be overcome by a contrary construction dictated by the written description or prosecution history. The Federal Circuit found that the prosecution history overcomes the presumption; the correct construction of "heterogeneous mixture" is one that excludes repetitive sequences, notwithstanding the presence of certain dependent claims that do not exclude them. The Federal Circuit therefore affirmed the grant of summary judgment of non-infringement.

The Federal Circuit then turned to summary judgment that certain products did not infringe under the doctrine of equivalents. The Federal Circuit said that a narrowing amendment made to satisfy any requirement of the Patent Act may give rise to an estoppel. The presumption of surrender, however, may be rebutted if the patentee can demonstrate that: (1) the alleged equivalent would have been unforeseeable at the time the narrowing amendment was made; (2) the rationale underlying the narrowing amendment bore no more than a tangential relation to the equivalent at issue; or (3) there was some other reason suggesting that the patentee could not reasonably have been expected to have described the alleged equivalent. LOF: Whether the district court erred in its application of prosecution history estoppel to limit the effect of the doctrine of equivalents is also a question of law that is reviewed de novo. The Federal Circuit analyzed whether the amendment was merely tangential. The inquiry into whether a patentee can rebut the Festo presumption under the ‘tangential’ criterion focuses on the patentee’s objectively apparent reason for the narrowing amendment. Prosecution history estoppel will not bar the doctrine of equivalents when the reason for the narrowing amendment was peripheral, or not directly relevant, to the alleged equivalent. The prosecution history therefore reveals that in narrowing the claim to overcome the prior art rejections, the focus of the patentees’ arguments centered on the method of blocking—not on the particular type of nucleic acid that could be used for blocking. Indeed, the "nucleic acid" limitation was never narrowed during prosecution and was not at issue in the office action rejecting the claims, the Examiner Interview Summary Record, or the patentees’ remarks accompanying the amendment. The Federal Circuit concluded that appellants have met their burden of showing that the amendment did not surrender the equivalent in question because the narrowing amendment was only tangential to the accused PNA equivalent, i.e., the peptide nucleic acid. The Federal Circuit found that the court erred in concluding that appellants were precluded by estoppel from asserting that defedant's products infringe under the doctrine of equivalents.