In EIDOS DISPLAY, LLC v. AU OPTRONICS CORP., Appeal No. 2014-1254, the Federal Circuit held a claim term was not indefinite when the specification used a similar term to describe a similar but unclaimed embodiment, because the embodiment revealed how a person of ordinary skill in the art would understand the disputed term.

Eidos sued LCD manufacturers for patent infringement.  After struggling with a disputed claim term during claim construction and on a motion for summary judgment of noninfringement, the district court ordered briefing on indefiniteness.  The district court rejected the parties’ proposed constructions and granted the manufacturers’ motion for summary judgment of indefiniteness.

The Federal Circuit reversed and held the disputed term was not indefinite.  The parties did not dispute there was a “well-established practice” regarding the term.  Nothing in the patent indicated that a person of ordinary skill in the art would deviate from this practice, and the only use of the term in the specification was consistent with the well-established practice.  Although the use was in the context of an unclaimed embodiment, the Federal Circuit held the description nevertheless informed the determination of how a person of ordinary skill in the art would understand the claimed limitation.