Federal Circuit Finds Use of Word “a” in Claim Limited Scope To A Single Element

In Norian Corp. v. Stryker Corp., the Federal Circuit affirmed the District Court’s grant of summary judgment of non-infringement based upon a narrow interpretation of the claim term “a.”  Specifically, Norian asserted infringement based upon claims 8-10 of U.S. Patent No. 6,002,065.  Claim 8 recites, among other features “a solution consisting of water and a sodium phosphate” with the sodium phosphate being in concentration of 0.01 to 2.0 M.  Claims 9 and 10 depend from claim 8 and recite different amounts of the sodium phosphate.  The District Court held that the solution recited in claim 8 requires a mixture having the recited range for a single type of sodium phosphate and does not cover solutions with mixtures of sodium phosphates.  Since Stryker’s accused solution includes a mixture of different types of sodium phosphates (i.e., monobasic sodium phosphate and dibasic sodium phosphate), the District Court held that there was no single type of sodium phosphate meeting claim 8.

In affirming the District Court’s opinion, the Federal Circuit noted that, while claim 8 recites “at least one calcium source” and “at least one phosphoric acid source,” claim 8 does not recite at least one sodium phosphate.  According to the Federal Circuit, if Norian had intended to cover more than one type of sodium phosphate, “it would have been simple to use the same language.”

Additionally, the Federal Circuit noted that, while the word “a” is generally open ended and means more than one, “a” is only open ended when open ended claim terminology is used.  As such, the word “a” following “comprising” can mean more than one.  However, where closed terminology such as “consisting of” is used or where there is evidence in the prosecution history that the word “a” is intended to mean a single item as opposed to more than one item, the word “a” is limited to a single item.  Since claim 8 uses closed terminology (consisting of), the District Court’s interpretation is supported by the claim language by itself.

Lastly, the Federal Circuit noted that, even assuming closed terminology was not used, the specification and the prosecution history support the more narrow interpretation.  Specifically, while each of the disclosed examples uses only a single sodium phosphate in the example solutions, there is no example or suggestion in the specification that a solution has multiple sodium phosphates.  The Federal Circuit further noted that, during prosecution, Norian had further made representations that the solution includes only a single sodium phosphate, and had represented to the Examiner that the specification’s examples show that the scope of the claimed invention was explicitly for sodium phosphates used individually and not in combination.  As such, the Federal Circuit upheld the District Court’s dismissal on the basis of non-infringement.

A copy of the case can be found at Norian Corp. v. Stryker Corp. 2005 U.S. App. LEXIS 26528, Civ. Case No. 05-1172 (Fed. Cir. December 6, 2005).


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