Decisions restating the doctrine of equivalents by English and German courts within the past year, especially in the Eli Lilly v Actavis litigations, suggest a review of how the DOE is applied in the US, writes John Pegram of Fish & Richardson.
In the US, infringement by equivalents is determined by use of two threshold legal tests and a factual test. Two of these three have been clarified by US courts this year.
Ensnarement of the prior art
As stated in September by the US Court of Appeals for the Federal Circuit, “a doctrine of equivalents theory cannot be asserted if it will encompass or ‘ensnare’ the prior art” (Jang v Boston Scientific)”. The modern expression of this legal principle and use of the term “ensnare” are derived from the US Supreme Court’s opinion in one of the leading DOE cases, Warner-Jenkinson v Hilton Davis (1997).
John Pegram, Fish & Richardson, doctrine of equivalents, Eli Lilly v Actavis litigations, US patent infringement, , patent, equivalents, prosecution