SW Legal Educational Publishing

All Patents Are Not Created "Equivalent"
Description US Supreme Court reversed and remanded patent infringement injuction because the lower courts failed to apply the doctrine of equivalents to individual elements of the patent and not the investion as a whole.
Topic Intellectual Property
Key Words Doctrine of Equivalents, Patents
C A S E   S U M M A R Y
Facts Both firms make dyes from which impurities must be removed. W-J received a patent for an improved purification process that operated at pH levels between 6.0 and 9.0. It was different from existing technologies that operated at a pH above 9.0. The next year, Hilton developed a similar process that operated at a pH of 5.0. W-J sued for patent infringement based on the "doctrine of equivalents," which holds that a process may not be an exact copy of a patented process (or product) but may be found to infringe if there is "equivalence" between the elements of the two processes. The jury found an infringement based on the doctrine. The District Court entered a permanent injunction against Hilton. The Federal Circuit affirmed. Hilton appealed.
Decision Reversed and remanded. The doctrine of equivalents is valid but must be applied to individual elements of patent claims, not to inventions as a whole. The changing of the pH is the key point here and it was not resolved if that step alone violated the doctrine, which may have been the case here. [That is, it was not clear why the patent had a lower pH bound of 6.0; it may be that the pH could have been set at 5.0 in the patent, or it could be that Hilton had a novel invention that extended knowledge that did not exist before.] The intent of an infringer is not relevant in determining if a patent has been infringed.
Citation Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 117 S.Ct. 1040 (1997)

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