April 23, 2024

Tullio Corradini

Trusted Legal Source

Prior Narrow Definition Does Not (Necessarily) Limit Claim Scope in Family Member

Prior Narrow Definition Does Not (Necessarily) Limit Claim Scope in Family Member

Finjan LLC v. ESET LLC, — F.4th — (Fed. Cir. 2022)

Finjan’s patents claim a system for checking downloadable files for security concerns.  Back in 1996 when Finjan filed its original provisional application, the focus was on applets or other small downloadable programs.  But downloadables today are much bulkier.  Here, the claims require a number of operations on “a downloadable” and the parties have debated throughout the litigation how to construe that term.

The district court’s approach was a bit convoluted.

  • Construction: The district court first narrowly construed the term as limited only to “small downloadables.” Although the asserted patents do not appears to require smallness, the patents do incorporate-by-reference a family member that particularly defines downloadable as “applets” and as “small executable or interpretable application program[s] which [are] downloaded.”
  • Invalidation: Later, the district court reviewed that construction and concluded that the term “small” is a term of degree without any limiting theory and therefor is invalid as indefinite.

On appeal, the Federal Circuit has reversed on the following point of law:

The use of a restrictive term in an earlier application does not reinstate that term in a later patent that purposely deletes the term, even if the earlier patent is incorporated by reference.

Slip Op.  The court further explained that patents within a family can use two different definitions of the same term.  “[T]hese two definitions can exist in harmony within the patent family.”  The court noted that the earlier application with the “small” limitation was focused on downloading small executables while the patents at issue in this case claim an invention with a changed-focus that is “not limited to ‘small’ executable[s].” Here, the court noted that the patentee had also incorporated by reference another prior patent that did not include the small limit.  For the appellate court, all this means that, for the asserted patents the downloadables are not required to be small.

I have included an image of the patent family tree from the patentee’s brief.  You can see that there are several branches.  I believe that it is those branches (rather than a straight-chain of continuations) that helped the court reach its decision that the family-member definitions were not binding.  The court noted some about of difference in the disclosures as well.

Since the “small” definition was eliminated, that also mooted the question of whether “small” is indefinite.