This is a patent infringement case that commenced as a trade secret dispute between two competitors in the non-chemical water treatment business. Clearwater Systems Corporation (“Clearwater”) brought an action in the U.S. District Court for the District of Connecticut (“district court”) against Evapco, Inc. (“Evapco”), as well as John W. Lane, a former Clearwater employee who was hired by Evapco, and Bullock, Logan & Associates (“Bul-lock”), a marketing consultant that provided marketing services for Clearwater and Evapco. Clearwater sought injunctive relief for alleged theft of trade secrets and other state business law torts. The district court concluded that Clearwater’s allegedly misappropriated information were not trade secrets under the Connecticut Uniform Trade Secrets Act and denied Clearwater’s request for a permanent injunction. Clearwater Sys. Corp. v. Evapco, Inc., No. 3:05-CV-507, 2005 WL 3543717, at *14 (D. Conn. July 26, 2005).Prior to the resolution of the trade secrets claim, Evapco counterclaimed for a declaratory judgment that its “Pulse-Pure” product did not infringe two of Clearwater’s patents, U.S. Patent No. 6,063,267 (“’267 patent”), disclos-ing an apparatus for non-chemical water treatment, and U.S. Patent No. 6,641,739 (“’739 patent”), disclosing a method of non-chemical water treatment. Evapco also counterclaimed for a declaration of invalidity and/or unenforceability of the ’267 and ’739 patents. In response, Clearwater amended its complaint to assert a claim of patent infringement against Evapco, alleging that the Pulse-Pure infringed the ’267 and ’739 patents.
The parties subsequently submitted cross-motions for summary judgment of literal infringement of the ’267 patent and invalidity of the ’267 and ’739 patents. After hearing arguments relating to the motions, the district court ruled that the ’267 patent is not invalid for anticipation, but concluded that the ’739 patent is invalid because it is inherently anticipated by the ’267 patent. Clearwater Sys., Corp. v. Evapco, Inc., 596 F. Supp. 2d 291, 313 (D. Conn. 2009). Furthermore, the district court ruled that the Pulse-Pure does not literally infringe the ’267 patent and sua sponte ruled that the Pulse-Pure does not infringe the ’267 patent under the doctrine of equivalents. Id. at 302, 308. For the reasons discussed below, we vacate and remand for proceedings consistent with this opinion.