Addressing the issue of claim construction and whether a preamble limits the claim, the U.S. Court of Appeals for the Federal Circuit vacated and remanded a grant of summary judgment in favor of the accused infringer, finding that the lower court had erred in finding a term in the preamble as limiting the claimed invention. In a strong dissent, Judge Dyk argued that everything in a claim should limit the scope of invention. American Medical Systems, Inc. v. Biolitec, Inc., Case No. 09-1323 (Fed. Cir., Sept. 13, 2010) (Bryson, J.) (Dyk, J., dissenting).

American Medical Systems appealed an order granting summary judgment of non-infringement to Biolitec. The patent in suit claims methods and devices for vaporizing tissue using laser radiation. The district court granted summary judgment based on its conclusion that Biolitec’s accused device does not perform "photoselective vaporization of tissue," a term that is recited only in the preamble of the asserted claims. American Medical appealed.

On appeal, the Federal Circuit concluded that, in this case, the preamble did not limit the asserted claims. Rather, the Court concluded that the preamble was merely a "descriptive name" for the set of limitations in the body of the claim. The Federal Circuit explained that whether a preamble is construed as a limitation depends on the facts of each case, but the general rule is that the preamble does not limit the scope of a claim when the body of the claim describes a structurally complete invention in such a way that deletion of the preamble does not affect the structure or steps of the claimed invention. The Court further explained that the preamble of a patent claim may be limiting "if it recites essential structure of steps, or if it is ‘necessary to give life, meaning, and vitality’ to the claim."

Judge Dyk, in dissent, suggested the Court review the issue en bancto eliminate its vague and confusing precedent regarding preambles. In his opinion, the Court should dispense with the current fact-based analysis of preambles and instead hold patentees to a strict rule by which each word included in a claim acts as a limitation. Under this rule, the patentee would be unable to suggest or imply one position to secure an allowance of the patent and a different, typically inconsistent position, during infringement litigation.

Practice Note: Consider limiting the length of your claim preambles and be sure that any fundamental characteristics of the invention appear in the body of the claim.