See Panduit Corp. v. All States Plastic Mfg. Co., 744 F.2d 1564, 1574-75, 223 USPQ 465, 471 (Fed. Cir. 1984). Although Ninth Circuit law is controlling, we looked to Under Sea Indus., Inc. v. Dacor Corp., 833 F.2d 1551, 4 USPQ2d 1772 (Fed. Cir. 1987), for guidance in the resolution of this issue.See Donovan v. Mazzola, 761 F.2d 1411, 1414 (9th Cir. 1985).

The district court held a bench trial on January 25–28, 2010, and March 13, 2010. The court relied on Under Sea Industries, Inc. v. Dacor Corp., 833 F.2d 1551, 1557 (Fed.Cir.1987), which states that “[t]he burden always is on the patentee to show infringement,” and thus held that “[a]s the parties asserting infringement, defendants bear the burden of proof by a preponderance of the evidence.” Opinion at 766.

The district court held a bench trial on January 25-28, 2010, and March 13, 2010. The court relied on Under Sea Industries, Inc. v. Dacor Corp., 833 F.2d 1551, 1557 (Fed. Cir. 1987), which states that "[t]he burden always is on the patentee to show infringement," and thus held that "[a]s the parties asserting infringement, defendants bear the burden of proof by a preponderance of the evidence." Opinion at 17.

But it nonetheless believed that Mirowski, “[a]s the part[y] asserting infringement,” bore the burden of proving infringement. Medtronic, Inc. v. Boston Scientific Corp., 777 F. Supp. 2d 750, 766 (Del. 2011); see Under Sea Industries, Inc. v. Dacor Corp., 833 F. 2d 1551, 1557 (CA Fed. 1987) (“The burden always is on the patentee to show infringement”). After a bench trial, the court found that Mirowski had not proved infringement, either directly or under the doctrine of equivalents.

To sustain a claim of inequitable conduct, the alleged infringer must show by clear and convincing evidence that (1) the nondisclosed information would have been material to the patent examiner, and (2) the nondisclosure was intentional. Under Sea Indus., Inc. v. Dacor Corp., 833 F.2d 1551, 1559 (Fed. Cir. 1987). These two elements must be balanced against each other, and if one is particularly strong, a lesser degree of the other may suffice to show inequitable conduct.

Whereas claim construction is a question of law, the determination whether infringement has occurred is a question of fact, with the burden of proof on the patentee to show infringement. See Baxter Healthcare Corp. v. SpectraMed, Inc., 49 F.3d 1575, 1582 (Fed. Cir. 1995); Under Sea Indus., Inc. v. Dacor Corp., 833 F.2d 1551, 1557 (Fed. Cir. 1987). Infringement occurs when a properly construed claim "reads on" the accused product.

Madey v. Duke Univ., 307 F.3d 1351, 1358 (Fed. Cir. 2002). As the patent owner, Jackson bears the burden of proving infringement. Under Sea Indus., Inc. v. Dacor Corp., 833 F.2d 1551, 1557 (Fed. Cir. 1987) ("The burden always is on the patentee to show infringement."). As noted at the outset of this opinion, the `900 patent describes a system made up of hard-wired, digital logic circuit elements.

Anderson, 477 U.S. 242, 249-50, 106 S.Ct. 2505, 91 L.Ed.2d 202 (internal citations omitted). Additionally, in a patent case, the owner of the patent always has the burden to prove infringement. Under Sea Industries, Inc. v. Dacor Corp., 833 F.2d 1551, 1557 (Fed. Cir. 1987). However, if a party challenges a patent's validity, that party has the burden to show invalidity by clear and convincing evidence.

Hence, in this case, plaintiff must demonstrate by a preponderance of the evidence that defendant engaged in conduct which infringes upon plaintiff's patent. Under Sea Industries, Inc. v. Dacor Corp., 833 F.2d 1551, 1557 (Fed Cir. 1987); Uniroyal, Inc., v. Rudkin-Wiley Corp., 837 F.2d 1044, 1054 (Fed. Cir. 1988). In response to this contention, defendant Joyce asserts that plaintiff has no protectible interest since the patent is invalid as it is anticipated by the prior art and obvious.

Streamfeeder's reliance on National Presto is misplaced, however, because while the burden of going forward rests with the accused infringer, the burden of persuasion that the hypothetical claim does not ensnare the prior art remains with the patentee: In this context it is important to remember that the burden is on Wilson [the patentee] to prove that the range of equivalents which it seeks would not ensnare the prior art. . . . The patent owner has always borne the burden of proving infringement, see Under Sea Indus., Inc. v. Dacor Corp., 833 F.2d 1551, 1557, 4 USPQ2d 1772, 1776 (Fed. Cir. 1987), and there is no logical reason why that burden should shift to the accused infringer simply because infringement in this context might require inquiry into the patentability of a hypothetical claim. Any other approach would ignore the realities of what happens in the PTO and violate established patent law.