potentially anticipatory patent); Henkel Corp. v. Procter & Gamble Co., 560 F.3d 1286
(Fed. Cir. 2009) (interference); Symantec Corp. v. Computer Assocs. Int’l, Inc., 522 F.3d
1279, 1295-96 (Fed. Cir. 2008) (“An alleged co-inventor's testimony, standing alone,
cannot rise to the level of clear and convincing evidence; he must supply evidence to
corroborate his testimony.”). However, this is not a case where witness testimony was
being used to overcome prior art by establishing an earlier date of invention.
To support its argument that S4 practiced the ’449 patent, Microsoft offered
specifically testimony by S4’s inventors, that S4 did not practice the claimed method.
Though we require corroboration of “any witness whose testimony alone is asserted to
invalidate a patent,” Finnigan Corp. v. Int’l Trade Comm’n, 180 F.3d 1354, 1369-70
(Fed. Cir. 1999) (emphasis added), here the inventor testimony was offered by i4i in
response to Microsoft’s attack on the validity of the ’449 patent. It was not offered to
meet Microsoft’s burden of proving invalidity by clear and convincing evidence. Cf.
TypeRight Keyboard Corp. v. Microsoft Corp., 374 F.3d 1151, 1159-60 (Fed. Cir. 2004);
Tex. Digital Sys., Inc. v. Telegenix, Inc., 308 F.3d 1193, 1217 (Fed. Cir. 2002); Finnigan,
180 F.3d at 1367. We know of no corroboration requirement for inventor testimony
asserted to defend against a finding of invalidity by pointing to deficiencies in the prior
art. Accordingly, we hold that corroboration was not required in this instance, where the
testimony was offered in response to a claim of anticipation and pertained to whether
the prior art practiced the claimed invention.