By Dave Maiorana

It is well-established that a counterclaim for invalidity in a district court litigation does not trigger the 35 U.S.C. § 315(a) bar.  See 35 U.S.C. § 315(a)(3).  See also our previous posts here and here discussing strategies for declaratory judgment claims.  But what if the patentee asserts fewer than all the claims of the patent-at-issue and the defendant files declaratory judgment counterclaims for invalidity of unasserted claims?  Does that trigger the bar?  That was the question before a panel of the Board in AMP Plus, Inc. (dba ELCO Lighting) v. DMF, Inc., Case IPR2019-01094.  The Board in this case answered the question in the negative.

In the companion district court litigation, patentee DMF filed a complaint alleging infringement of “at least claim 1 and its dependent claims.”  Defendant ELCO filed an answer and counterclaims in due course.  Later, DMF filed an identification of asserted claims, listing claims 1-2, 4-22, 25, 26, 28 and 29.  DMF then filed formal infringement contentions, asserting only claims 1, 2, 5, 7, 9–11, 13, 15–16, and 30.  ELCO filed a second amended answer and counterclaims, seeking a declaratory judgment of invalidity of the asserted claims plus unasserted claims 12, 17, 20, 22, and 27.  ELCO later filed an IPR seeking review of both asserted and unasserted claims.  DMF moved to dismiss the IPR, arguing that ELCO’s counterclaim for invalidity of unasserted claims triggered the 315(a) bar.

DMF asserted to the Board that at the time that ELCO filed its second amended declaratory judgment counterclaim, it went beyond the scope of DMF’s asserted claims.  DMF contended that the Board must conduct the 315(a) analysis on a claim-by-claim basis.  Because, according to DMF, ELCO’s counterclaim included claims 12, 17, 20, 22, and 27, which were unasserted at the time of that counterclaim, the counterclaim was not compulsory and thus barred ELCO’s later-filed IPR under 315(a).  ELCO argued that its counterclaims were compulsory and that

Section 315 considers any counterclaim challenging the validity of a claim in an asserted patent to be a counterclaim pursuant to § 315(a)(3), not a new civil action pursuant to § 315(a)(1).

The Board agreed with ELCO and denied the motion.  First, the Board found that the language of 315(a)(3) supports ELCO’s position because it says a counterclaim challenging validity does not constitute a civil action challenging validity.  Second, the Board found that Fed. R. Civ. Pro. 13 supports  ELCO’s position that its counterclaims were compulsory, even as against unasserted claims.  Finally, the Board disagreed that the 315(a) analysis must be done claim-by-claim.  Even if it did, the Board reasoned, the record in the district court showed that it was unclear exactly which patent claims DMF was asserting such that ELCO’s counterclaim included claims that DMF appeared to have been asserting as some point during the litigation.  The Board expressly distinguished the situation where a defendant seeks a declaratory judgment counterclaim of a previously unasserted patent, not unasserted claims in an otherwise asserted patent.


Defendants in patent infringement litigation need to carefully consider whether and when to file declaratory judgment counterclaims seeking a finding of invalidity if they have not already filed an IPR against the claims that may form the basis for the counterclaims.  Section 315(a)(3) is clear on its face, but this decision shows that an unwary petitioner can still find itself under scrutiny for its actions prior to filing an IPR petition.


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Dave Maiorana is a trial lawyer with a notable combination of significant experience as a United States Patent and Trademark Office (USPTO) Examiner and more than 25 years litigating complex intellectual property matters. He has represented clients as both plaintiffs and defendants around the country and in the International Trade Commission (ITC). Dave has experience in diverse technology areas, including e-cigarettes, teeth whitening, diapers, fem care, antibodies, self-inflating tires, oxygen concentrators, flash memory, and digital cameras.