“The court has taken this case in banc to clarify and apply principles of laches and equitable estoppel which have been raised as defenses in this patent infringement suit.”
“In summary . . . we hold with respect to laches: 1. Laches is cognizable under 35 U.S.C. § 282 (1988) as an equitable defense to a claim for patent infringement. 2. Where the defense of laches is established, the patentee’s claim for damages prior to suit may be barred. 3. Two elements underlie the defense of laches: (a) the patentee’s delay in bringing suit was unreasonable and inexcusable, and (b) the alleged infringer suffered material prejudice attributable to the delay. The district court should consider these factors and all of the evidence and other circumstances to determine whether equity should intercede to bar pre-filing damages. 4. A presumption of laches arises where a patentee delays bringing suit for more than six years after the date the patentee knew or should have known of the alleged infringer’s activity. 5. A presumption has the effect of shifting the burden of going forward with evidence, not the burden of persuasion. With respect to equitable estoppel against a patent infringement claim, we hold that: 1. Equitable estoppel is cognizable under 35 U.S.C. § 282 as an equitable defense to a claim for patent infringement. 2. Where an alleged infringer establishes the defense of equitable estoppel, the patentee’s claim may be entirely barred. Three elements must be established to bar a patentee’s suit by reason of equitable estoppel: a. The patentee, through misleading conduct, leads the alleged infringer to reasonably infer that the patentee does not intend to enforce its patent against the alleged infringer. Conduct may include specific statements, action, inaction, or silence where there was an obligation to speak. b. The alleged infringer relies on that conduct. c. Due to its reliance, the alleged infringer will be materially prejudiced if the patentee is allowed to proceed with its claim. 4. No presumption is applicable to the defense of equitable estoppel.”
