Does the Preamble Constitute a Limitation of the Claim?

On September 13th, the United States Court of Appeals for the Federal Circuit decided American Medical Systems, Inc. v. Biolitec, Inc., which involved an important issue in patent claim interpretation: when does the preamble of a patent claim constitute a limitation of that claim?

For the uninitiated, a patent claim defines the scope of protection conferred by the patent and is usually divided into three separate parts: a preamble, a transitional phrase, and a body.  The preamble comes first and is often used to describe the environment in which the invention resides, to describe a field of intended use, and/or to provide antecedent basis for (i.e., to introduce) one or more terms in the claim body.  As an example, a representative claim from the patent involved in American Medical Systems is shown below with its preamble underlined and in boldface:

31.        A method for photoselective vaporization of tissue, comprising:

delivering laser radiation to a treatment area on the tissue, the laser radiation having a wavelength and having irradiance in the treatment area sufficient to cause vaporization of a substantially greater volume of tissue than a volume of residual coagulated tissue caused by the laser radiation, wherein the delivered laser radiation has an average irradiance in the treatment area greater than 10 kiloWatts/cm2 in a spot size at least 0.05 mm2.

In this case, the majority found that the above preamble phrase “photoselective vaporization of tissue” did not constitute a limitation of the claim.  The majority found it significant that the preamble: (1) merely describes the invention set forth in the body of the claim; (2) was not used to overcome prior art; and (3) was not necessary to provide antecedent basis for the term “tissue” (even though it was used for this purpose).

Before announcing its decision, the Court reviewed the case law in this area and summarized the general guidelines for determining whether a preamble constitutes a claim limitation:

1.         Generally, a preamble does not limit a claim

2.         Whether a preamble limits a claim is determined based on the facts of each case in light of the claim as a whole and the invention described in the patent

3.         A preamble phrase will limit a claim where the phrase: (a) recites essential structure or steps; (b) is necessary to give “life, meaning, and vitality” to the claim; or (c) was added during prosecution to overcome prior art

4.         A preamble phrase will not limit a claim where: (a) the deletion of the phrase does not affect the structure or steps of the claimed invention; (b) the phrase is duplicative of the limitations in the claim body; or (c) the phrase is merely descriptive

As readily argued by the dissent, these guidelines will be difficult to apply in some cases, and this entire body of law should probably be reviewed by the Court en banc.  Until then, however, patent applicants and their attorneys must carefully consider the implications of these guidelines when drafting patent claims or conducting non-infringement or invalidity investigations.

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Andrew Haynes

About Andrew Haynes

Andrew Haynes concentrates his practice on intellectual property matters with a focus on patent and trademark prosecution. He is registered to practice before the U.S. Patent and Trademark Office. Andrew’s practice includes drafting and prosecuting domestic and foreign patent applications that cover a wide range of industries, including those in the mechanical, electrical, software, and business method fields. He also regularly conducts freedom-to-practice, invalidity, and infringement investigations, and has experience counseling clients on a variety of intellectual property matters.


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