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Two Contexts for Interpretation of Claim Terms

Posted Sunday, January 22, 2012 by Mike Gibbons

The intellectual property an inventor regards as his or her own is detailed in a set of patent claims. Analogous to the legal description of a parcel of real estate included in a title to a home, patent claims precisely describe the boundaries of invention. Patent claims provide notice to other parties exactly what the patented invention is, so that another party doesn’t inadvertently infringe the patent. This is akin to placing a fence on the property lines of a home, so that would-be trespassers know where to find the boundary that shouldn’t be crossed.

An important difference between a legal description of real estate and a patent claim, however, is that the terminology of a real property legal description is standardized, while the terminology of a patent claim varies with the invention itself. Thus, during the patent examination process, a patent examiner takes care to ensure that the terms used in the patent claim are clearly defined and have meanings that would be easily understood by one reading the patent claim.

This can be trickier than one might imagine. Consider a patent claim for a chemical compound to “restore hair growth.” Does “restore hair growth” mean to return a full head of hair? Or does it mean to get some amount of hair growing again? In order for the patent to issue, the meaning of “restore hair growth” would have to be clarified so as to provide the notice to others discussed above.

Of course, what seems clear to a patent examiner who allows a patent might not seem clear to everyone. Occasionally, that lack of clarity becomes the basis for a patent infringement suit. In other words, a patent-holder and an accused infringer might disagree on what a claim term means. From the standpoint of the accused infringer, infringement may not have occurred because what the accused infringer produced isn’t within the accused infringer’s interpretation of the meaning of the patent claim. Conversely, the patent-holder may believe the patent claim has a different meaning, one which encompasses the item the accused infringer produced. In a patent litigation suit, such a dispute would be resolved judicially.

Consequently, the precision and clarity of a patent claim may be considered in two different contexts: first, during the prosecution of the application, and second, in litigation after the patent has been issued.

During prosecution, an examiner may require the applicant to revise the proposed patent claims to increase the precision and clarity of a claim. Claims need to be concise, however. For example, say the examiner feels “restore hair growth” is indefinite. It may not be practical to provide a definition for “restore hair growth” in the claim itself, because the claim might get lengthy. So we look to the specification, including the detailed description that is a part of every patent application, to see if the meaning of “restore hair growth” is more apparent. If there is additional definition in the specification, the patent claim may be refined in accordance with the detailed description.

In the litigation context, when the opposing parties assert the patent claim has different meanings, the specification and detailed description is again consulted to ascertain what the patentee meant by a particular claim term. If the meaning of the term is not apparent, the court may consult additional sources to arrive at the meaning. There is a hierarchy for the values a court should apply to different types of additional source.

This leads to an important principle for preparing the content of an application for a patent. Detailed descriptions have to be carefully crafted to provide meaning for claim terms. During patent prosecution, if patent claims must be revised for a patent to issue, a patent attorney or patent agent must limit the revisions to content taken from the application as it was originally filed, or limit the refinements to claim terms that would be commonly understood. There is a prohibition on appending new matter into an application after it is filed. It is difficult to clarify patent claims with language that didn’t appear in the original application.

If one assumes that a claim term has an easily understood meaning and that assumption turns out not to be correct, there might be an unexpected challenge ahead during patent prosecution. Even if one is able to come to an agreement with the patent examiner resulting in an issued patent, a claim term appearing ambiguous might still be subject to additional scrutiny in patent litigation.

Two Contexts for Interpretation of Claim Terms ›› Ruttler Mills PLLC