Defending the Patent Case – Make Sure to Serve This Interrogatory

Patent cases are very discovery intensive, and many courts now have “patent local rules” that provide regulated process by which plaintiffs disclose their infringement contentions (i.e., explanations of why the defendant’s acts infringe the plaintiff’s patent) and by which defendants disclose their invalidity contentions (i.e., explanations of why the plaintiff’s patent claims are invalid). These contentions are intended to flesh out disputes over what particular patent claim terms mean, and the court resolves those disputes as a matter of law, typically after conducting what is known as a “Markman Hearing.”

There is one piece of discovery that can be very helpful to a defendant and which is not usually required by patent local rules. If you are defending a patent case, I would strongly recommend that you serve an interrogatory that requires the patent holder to map the claim elements to the corresponding features in the patent specification’s embodiments. Patent holders want to apply their claims in a way that covers a defendant’s accused product while avoiding the prior art. In some cases, they avoid defining claim terms explicitly but then apply them to the accused product and the prior art inconsistently and try to camouflage the inconsistency. Toward that end, patent holders will often seek claim constructions that are so tautological as to be virtually meaningless.

Forcing the patent holder to identify where each claim term is found in the embodiments can provide a check against the patent holder’s use of implicit claim constructions that cannot be reconciled with the specification embodiments. Generally, courts are reluctant to adopt claim constructions that exclude or “read out” embodiments of the asserted patent, and forcing the patent holder to map the claim language to the embodiments can reveal that it is doing just that. Otherwise, the patent holder may just seek a construction that covers the accused product notwithstanding any inconsistency with the patent’s teachings.

Also, a response to this type of discovery may show that certain claim terms are not depicted or described anywhere in the specification, which can provide significant ammunition if you seek to invalidate the claims for violating the written description and/or enablement requirements of the Patent Statute. We recently worked on a couple of cases where this type of interrogatory had not been served, and it allowed the patent holder to play fast and loose with the meaning of claim language. A patent holder does not have a legitimate basis for refusing to respond to this type of interrogatory, and in our experience, it can be very helpful.