A.C. Aukerman Company, 960 F.2d at 1041. See also ABB Robotics, Inc. v. GMFanuc Robotics Corporation, 52 F.3d 1062 (Fed. Cir.), cert. denied, ___ U.S. ___, 116 S.Ct. 306, 133 L.Ed.2d 211 (1995). In contrast to laches, equitable estoppel focuses upon the reasonableness of the Defendant's conduct.

[CL5] With respect to the first element, making an accusation of infringement and then "not follow[ing] up for years" may provide a basis for an equitable estoppel defense when such conduct is also "combined with other facts respecting the relationship or contacts between the parties . . . giv[ing] rise to the necessary inference that the claim against the defendant is abandoned." Aukerman, 960 F.2d at 1042 (emphasis added); see also ABB Robotics, Inc. v. GMFanuc Robotics Corp., 52 F.3d 1062, 1064 (Fed. Cir. 1995) ("We agree with the trial court that CM's long period of inaction after GMF had denied infringement combined with the 'other factors' found by the trial court led GMF to reasonably conclude that CM did not intend to enforce the '536 patent against it."); Meyers v. Brooks Shoe Inc., 912 F.2d 1459, 1462 (Fed. Cir. 1990) ("[A] mere verbal charge of infringement, if made, followed by silence [is] not sufficient affirmative conduct to induce a belief that [Plaintiff] had abandoned an infringement claim."), overruled on other grounds by Aukerman, 960 F.2d 1020. [CL6]Deckers Outdoor Corp. v. Romeo & Juliette, Inc., No. 2:15-cv-02812, 2017 WL 2588065 (C.D. Cal. June 13, 2017), upon which Defendant relied, (Dkt. No. 852, 6/29/2017 P.M.

Knowledge as to whether the device itself actually infringe[d] one's patent is not required to establish laches." Thomas v. Echostar Satellite LLC, 2006 U.S. Dist. LEXIS 91748, at *15 (W.D.N.C. Dec. 19, 2006) (citing ABB Robotics, Inc. v. GMFanuc Robotics Corp., 52 F.3d 1062, 1391 (Fed. Cir. 1995)); id. ("It is settled that the laches period begins when the plaintiff discovers the facts which create his right or cause of action . . . . Even if Dr. Coleman did not know whether the Corvac was technically an 'infringement'. . . he knew all the facts concerning the Corvac project.").

Where established, it may bar all relief on a claim. See id.; ABB Robotics, Inc. v. GMFanuc Robotics Corp., 52 F.3d 1062, 1063 (Fed. Cir. 1995). There are three essential elements to an equitable estoppel claim:

1994) (constructive knowledge where patentee's agent saw challenged device at several trade shows, obtained and examined samples and consulted with patent counsel); Teradyne, Inc. v. Hewlett-Packard Co., 1994 WL 327213 at *7-8 (N.D.Cal. June 24, 1994) (constructive knowledge where patentee's researcher attended conference on challenged device, composed memo, and sent memo with manuals on device to legal counsel); ABB Robotics, Inc. v. GMFanuc Robotics Corp., 828 F. Supp. 1386, 1391 (E.D.Wis. 1993) (constructive knowledge where patentee saw challenged device at exhibition and later discussed with infringer possibility of infringement), aff'd, 52 F.3d 1062 (Fed. Cir. 1993). R2's infringement claims rest upon the alleged similar structure between Katecho's and R2's electrodes and its assertion that Katecho's electrodes use stannous chloride "affixed" to their tin surface.

"[A] party advancing an estoppel defense must prove each of the elements." ABB Robotics, Inc. v. GMFanuc Robotics Corp., 52 F.3d 1062, 1064 (Fed. Cir. 1995) (citation omitted). "[T]he court must consider all evidence relevant to the equities."

Equitable estoppel is a flexible doctrine that is "committed to the sound discretion of the trial judge." ABB Robotics, Inc. v. GMFanuc Robotics Corp., 52 F.3d 1062, 1063 (Fed. Cir. 1995). It is "not limited to a particular factual situation nor subject to resolution by simple or hard and fast rules."

The evidence also establishes that Defendants suffered economic prejudice through expenditures that would not have occurred if Plaintiffs had filed their lawsuit sooner. See, e.g., ABB Robotics v. GMFanuc Robotics Corp., 52 F.3d 1062, 1062–64 (Fed.Cir.1995). 2.4 Equitable Estoppel Bars Post–Suit Recovery

Id. "Misleading action by the patentee may be silence, if such silence is accompanied by some other factor indicating that the silence was sufficiently misleading to amount to bad faith." ABB Robotics v. GMFanuc Robotics Corp., 52 F.3d 1062, 1064 (Fed. Cir. 1995). "In the cases that have applied intentionally misleading silence in the patent infringement context, a patentee threatened immediate or vigorous enforcement of its patent rights but then did nothing for an unreasonably long time."

Misleading action or communication by the patentee may be "silence, if such silence is accompanied by some other factor indicating that the silence was sufficiently misleading to amount to bad faith." ABB Robotics, Inc. v. GMFanuc Robotics Corp., 52 F.3d 1062, 1064 (Fed. Cir. 1995) (citations omitted). Zimmer asserts that Howmedica cannot rely on silence alone to satisfy the requirements of equitable estoppel. Rather, Zimmer asserts that the period of silence must have been preceded by a threat of immediate and vigorous enforcement.