Two recent District Court decisions (D. Mass. and E.D. Tex.) highlight the increased difficulty faced by defendants when seeking to supplement invalidity contentions. In one decision, Canrig Drilling v. Omron, Judge Davis (E.D. Tex.) denied defendant's request to supplement its invalidity contentions because the "delay" in presenting the items was not explained.

In another decision, Abbott v. Centocor, Judge Saylor (D. Mass) denied defendant's request to supplement its invalidity contentions "to account" for the Court's claim construction order because the reasons for changes were not articulated. The Court reasoned that: