Think Before You Draft: Patent Prosecution Has Consequences For Patent Litigation

Time 7 Minute Read
December 5, 2023
Legal Update

The Federal Circuit recently issued several opinions focused on claim construction, specifically Salazar, Finjan, ABS Global, and Actelion. The first three deal with the issue of whether a term is singular or plural within the context of the claim and the last addresses interpretation of a claimed range. These cases, outlined below, offer important lessons in patent drafting for prosecutors and serve as a reminder that careful drafting can be vital to subsequent litigation.


In Salazar v. AT&T Mobility LLC, 64 F.4th 1311 (Fed. Cir. 2023), the appeal centered on the meaning of the claim terms “a microprocessor” and “said microprocessor.”

The patent owner argued the terms require one or more microprocessors, any one of which may be capable of performing the claimed actions, but the district court construed the terms to mean “one or more microprocessors, at least one of which is configured to perform” the claimed actions in the claim (emphasis added). The Federal Circuit affirmed the district court, confirming that “a” may mean “one or more” in open-ended claims and “said” does not change the general plural rule for “a.”

The Court distinguished the patent owner’s proposed construction, finding it would require “any one of the one or more” processors perform each claimed function, which is at odds both with Federal Circuit precedent and with the use of “said” microprocessor. In reaching this conclusion, the Court relied on its prior opinion, In re Varma, 816 F.3d 1352 (Fed. Cir. 2016), stating, “[f]or a dog owner to have a dog that rolls over and fetches sticks, it does not suffice that he has two dogs, each able to perform just one of the tasks” (internal quotations omitted).

Finjan and ABS Global

In Finjan LLC v. SonicWall, Inc., 84 F.4th 963 (Fed. Cir. 2023) and ABS Global, Inc. v. Cytonome/St, LLC, 84 F.4th 1034 (Fed. Cir. 2023), the Federal Circuit also considered whether claim terms were singular or plural. In Finjan, the term at issue was “a computer.” In ABS Global, the term at issue was “the sample stream.” The Court reached opposite conclusions in these cases.

In Finjan, the Federal Circuit’s holding was along the same lines as in Salazar; that is, the Court found that the same computer that satisfies the “a computer” limitation must perform the subsequent functions listed in the claims.

In contrast (but relying on Salazar), in ABS Global, the Federal Circuit found that the “the” in the term “the sample stream” refers back to the first instance of the term and takes any singular or plural meaning thereof. The Court observed that two factors “strongly support” a plural meaning here. First, the use of “a” generally allows for a construction of “one or more.” Second, there is language in the patent specification demonstrating that terms such as “a” or “an” could refer to one or more of an entity and “a” or “an” and “one or more” or “at least one” could be used interchangeably. This is key: the Federal Circuit noted that this specification language “brought into play the lexicography principle—that, with narrow exceptions, [w]here the specification instructs as to the meaning of a claim term the inventor’s lexicography governs” (internal quotations omitted). The Court also looked at dependent claim 2 and observed that the narrowing limitation in this claim did not support confining the term to a singular meaning.


Finally, in Actelion Pharmaceuticals LTD v. Mylan Pharmaceuticals Inc., No. 2022-1889, 2023 WL 7289417 (Fed. Cir. Nov. 6, 2023), the Federal Circuit held that the district court must consider extrinsic evidence to determine how a person of ordinary skill in the art would understand the claim language, “a pH of 13 or higher.”

During claim construction, both parties proposed plain and ordinary meaning for the term, but disagreed on what that meaning is. Citing three chemistry textbooks that discuss pH measurement errors and significant digits, Actelion argued the number is “subject to rounding” and proposed that, e.g., a pH of 13 could mean 12.5 rounded to 13. Mylan argued that the claim language did not allow for any pH values less than 13, further noting that if the court were inclined to consider pH measurement errors, Actelion’s textbooks supported only a narrow range of 12.995-13.004. The district court reasoned that the claims consistently used two significant digits for pH and no further precision is needed; thus, the term “a pH of 13” includes values that round up or down to 13.

The Federal Circuit remanded, faulting the district court for not reviewing the extrinsic evidence offered by the parties (including the chemistry textbooks) as part of the claim construction process. The Court found that turning to extrinsic evidence is required here because the specification and prosecution history do not provide sufficient clarity as to the proper interpretation of the claimed range.


These cases are a reminder that a specification should be drafted clearly and provide specific support for claim terms, particularly terms that include ranges and/or words that may be interpreted as singular or plural.

A good specification will include details on the architecture of the claimed embodiments. For example, if there are “multiple processors,” how many processors are there? It will also detail how entities perform any claimed functions. For example, again, if there are “multiple processors,” which processors perform which functions? Does one perform all functions or can different processors from a plurality perform different functions?

A patent drafter should also ensure that clarity carries over into the claim language, where practical. For example, if a range is part of a claimed embodiment, the drafter should include details regarding the range in the specification, with consistency, as well as details regarding what range is suitable for a claimed embodiment (is a range permitted above and below a certain threshold?). You likely do not want the court deciding whether 13 means 13 or 12.5 or 12.9 or 12.995 or all of the above.

Including boilerplate language in a specification, such as that used in ABS Global, is important when it comes to claim interpretation. Such language was lacking in Finjan, which is perhaps a factor in why the Federal Circuit came to an opposite holding in that case. Also, as demonstrated in ABS Global, carefully crafted dependent claims can serve to clarify the scope of an independent claim and reinforce desired interpretation of claim terms.

Finally, a patent drafter would be wise to make sure that claims track the disclosure of the specification as closely as practical to try to ensure the interpretation of the claim language is in line with the invention. Patent prosecutors often draft broad claims in order to achieve the widest coverage for a patent. But broad language can have drawbacks when it comes to patent litigation and seeking a claim construction to support infringement, particularly if the specification and prosecution history lack clarity—as the cases discussed above illustrate.

Accordingly, and perhaps the greatest takeaway of these recent cases: when drafting claims, it is important to not just “draft away” in a bubble, but also to think about how the claims might be interpreted down the road in litigation.

Jump to Page