infringement, are supported by substantial evidence. We disagree: the verdict must be
upheld if substantial evidence supports either legal theory. Microsoft’s argument fails to
distinguish between defects in legal theories and defects in the factual evidence. In this
case, the jury was instructed that it could rely on any of three legal theories—direct,
contributory, or induced infringement. All of these theories are legally valid and the
corresponding instructions on each were proper. Because the jury could not have relied
on a legally defective theory, the only remaining question is whether there was sufficient
evidence to support either of i4i’s independently sufficient legal theories, contributory
infringement or induced infringement.1 We conclude that there was.
1. Direct Infringement
To succeed on a theory of contributory or induced infringement, i4i was required
to show direct infringement of the ’449 patent. Lucent, 580 F.3d at 1317; see also
Glenayre Elecs., Inc. v. Jackson, 443 F.3d 851, 858 (Fed. Cir. 2006). Because the
claims asserted by i4i are method claims, Microsoft’s sale of Word, without more, did
not infringe the ’449 patent. Lucent, 580 F.3d at 1317. Direct infringement occurs only
when someone performs the claimed method. Id.
Based on the evidence presented at trial, a reasonable jury could have found that
at least one person performed the methods claimed in the ’449 patent. This evidence
included testimony by i4i’s expert (Dr. Rhyne), a joint stipulation, and Microsoft’s
response to interrogatories. Rhyne opined that Word’s custom XML editor met all of the
1 Even though we could affirm the jury’s verdict of infringement so long as there was sufficient evidence of direct infringement by Microsoft, here we focus on indirect infringement because that was the basis for i4i’s damages estimate, which the jury apparently credited. See Lucent, 580 F.3d at 1334-35; Dynacore Holdings Corp. v. U.S. Philips Corp., 363 F.3d 1263, 1274 (Fed. Cir. 2004).