O2 Micro Intern. Ltd. v. Monolithic Power Systems, Inc.

O2 Micro International Limited and O2 Micro, Inc. (collectively, O2 Micro) (plaintiffs) filed a claim for patent infringement against Monolithic Power Systems, Inc. (Monolithic) (defendant) in the United States District Court for the Northern District of California. The preliminary infringement contentions filed by O2 rested on one theory of infringement. After a claim-construction hearing, O2 served its final infringement contentions, which relied solely on the previously identified theory of infringement. The discovery process continued, and O2 deposed James Moyer, Monolithic’s chief integrated-circuit engineer. Almost three months after deposing Moyer, O2 sent supplemental infringement contentions to Monolithic that relied on a new theory of infringement, which O2 stated it discovered during Moyer’s deposition. O2 offered no explanation for the delay of several months in amending the contentions. Monolithic objected to the new contentions based on the new theory of infringement. O2 formally filed a motion to amend two weeks after sending the supplemental contentions. O2’s motion for leave to amend the contentions was denied. Monolithic filed a motion for summary judgment for noninfringement. In its response to the motion for summary judgment, O2 raised a new, third theory of infringement. The court granted the motion for summary judgment, relying solely on the initial theory expressed in the preliminary and final infringement contentions and finding no support for that theory in the record. O2 appealed.