Is there any possible danger in using the abbreviation “i.e.” in the specification of a U.S. patent application?  The Federal Circuit’s recent decision in TF3 Limited v. TRE Milano, LLC shows that the answer is “yes.”  The court provided a reminder that use of “i.e.” in the specification signals an intent to define the term to which it refers.  Thus, the court held that the term cannot be interpreted to be broader than the definition provided in the specification by the use of “i.e.” when interpreting the term under the broadest reasonable interpretation standard before the U.S. Patent and Trademark Office.

More particularly, in this case the Federal Circuit reviewed a Patent Trial and Appeal Board (PTAB) decision in an inter partes review (IPR) of U.S. Patent No. 8,651,118 (the ‘118 Patent).  Representative claim 1 of the ‘118 Patent reads, with emphasis added:

1. A hair styling device having:

         a body defining a chamber adapted to accommodate a length of hair, the chamber having a primary opening through which the length of hair may pass into the chamber;

         a rotatable element adapted to engage the length of hair adjacent to the primary opening;

         an elongate member around which, in use, the length of hair is wound by the rotatable element, the elongate member having a free end;

         the chamber having a secondary opening through which the length of hair may pass out of the chamber, the secondary opening being located adjacent to the free end; and

         a movable abutment which can engage the length of hair in use, the movable abutment having an open position in which the length of hair can pass through the secondary opening, and a closed position in which the length of hair is retained within the chamber, wherein the movable abutment is located within one of (i) the secondary opening, (ii) the primary opening, and (iii) a passageway connecting the secondary opening to the primary opening.

Of relevance to the court’s reliance on the use of the term “i.e.” in the specification, the court reviewed the district court’s claim interpretation of “the length of hair can pass through the secondary opening.”  The Federal Circuit held that the district court erred in its broadest reasonable interpretation of this claim language because it resulted in an unreasonably broad interpretation that read the claims more broadly than the specification by not requiring the length of hair to pass through and out of the secondary opening.  The court pointed to a sentence in the specification stating that “the abutment 52 in its open position allows the styled length of hair to pass out of the secondary opening 50, i.e. to slide along the elongate member 20 towards and subsequently off its free end.”  The court cited to its earlier decisions in Edwards Life Sciences LLC v. Cook Inc. and SkinMedica, Inc. v. Histogen Inc. in support of the proposition that the use of the term “i.e.” in this sentence of the ‘118 Patent signifies an intent for the length of hair to pass through and out of the secondary opening.

This case thus serves as a good reminder to carefully evaluate during patent application drafting whether to use the term “i.e.” in the specification in view of how its use can affect claim interpretation under the broadest reasonable interpretation standard during prosecution or before the PTAB.