The district court in a patent infringement case granted plaintiff’s ex parte request to strike defendant’s prior use defense under 35 U.S.C. § 273. Because defendant failed to plead the defense and did not raise it until just prior to the final pretrial conference, the court struck the defense as untimely.

Amended by the America Invents Act in 2011, Section 273 provides a noninfringement defense to a claim for patent infringement based on the defendant’s prior commercial use of the claimed product. This defense is separate and distinct from an invalidity defense based on prior public use under Section 102(a). And to rely on it, the defendant must introduce clear and convincing evidence that the defendant commercially used a product that meets the claim limitations prior to the effective filing date of the claims.

Here, after the court granted plaintiff’s motion for summary judgment of no invalidity, defendant sought to raise a defense under Section 273. In response, plaintiff filed an ex parte request to strike the defense as untimely. According to plaintiff, the first-time defendant had raised the defense was in its pretrial Memorandum of Contentions of Fact and Law. Defendant argued that it had pleaded facts consistent with a prior use defense. But the court struck the defense, holding that defendant had to actually plead a prior commercial use defense to infringement and could not merely rely on background facts consistent with the defense to establish that the defense had been timely raised. The court noted that the statutory language of Section 273(f), which requires a reasonable basis for asserting the defense, also suggests that the defense must be actually pleaded. 

Relatedly, the court granted-in-part plaintiff’s motion in limine seeking to exclude defendant’s arguments and evidence comparing its own products to prior art devices. Defendant argued that these comparisons were relevant to plaintiff’s infringement claims, defendant’s prior use defense to infringement and damages. Because the court struck defendant’s purported prior commercial use defense as untimely and concluded that the evidence was irrelevant to infringement, the court excluded defendant’s evidence and arguments suggesting that its own products practice the prior art. The court did, however, refrain from excluding defendant’s arguments and evidence for the narrow purpose of potentially rebutting plaintiff’s willful infringement arguments by showing that defendant had a good faith belief that the asserted patents were invalid. 

Practice Tip: Although some defendants may be hesitant to rely on Section 273, which requires clear and convincing evidence that the accused product meets the claim limitations, the defense may still be useful where, for example, infringement is not contested. But if a defendant wants to assert the prior commercial use defense, the defense should be raised expressly in the pleadings to avoid waiver. Alleging facts that are merely consistent with the defense will not be sufficient. 

Delta T LLC v. MacroAir Technologies, Inc., Case Nos. 5:20-cv-00728-GW-GJS, D.I. 399 (C.D. Cal. Apr. 19, 2024).