Finjan LLC v. ESET, LLC, Appeal No. 2021-2093 (Fed. Cir. 2022).

The Federal Circuit reversed a district court’s summary judgment that interpreted the claims based on a definition in a separate patent that was incorporated by reference.

The patents at issue are directed to systems and methods for detecting computer viruses in a Downloadable. A non-asserted family member patent defines the term “Downloadable” as “a small executable or interpretable application program which is downloaded from a source computer and run on a destination computer.”[1] Two of the asserted patents define “Downloadable” without using the term “small.” Though they do incorporate by reference a patent that does define a Downloadable as “a small executable ….”

The district court construed the term “Downloadable” to be restricted to “small” executable applications based on the definition of Downloadable in the family member patent that was incorporated by reference. The word “small” was determined to be indefinite, so the claims were invalid.

Claims are read in light of the specification, which includes any patents that are incorporated by reference. The incorporated references are effectively part of the specification and can be used to construe the claims.[2] While they may be part of the specification, the Federal Circuit explained that “incorporation by reference does not convert the invention of the incorporated patent into the invention of the host patent.”[3] The error was that the district court decided that the claims should be limited to the most restricted definition of Downloadable. It was not necessary to limit the term, especially since the asserted patents purposely deleted the term “small” despite incorporating by reference the earlier patent.

Consequently, the claim term “Downloadable” does not include the indefinite term “small” and the district court’s determination of invalidity due to indefiniteness was reversed.


[1] Finjan LLC v. ESET, LLC, Appeal No. 2021-2093, at 4 (Fed. Cir. 2022), citing U.S. Patent No. 6,167,520, at col. 1, ll. 31-34.

[2] Id. at 7.

[3] Id. at 8, quoting Modine Mfg. Co. v. U.S. Int’l Trade Comm’n, 75 F.3d 1545, 1553 (Fed. Cir. 1996), abrogated on other grounds by Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 234 F.3d 558 (Fed. Cir. 2000) (en banc).