Doctrine of Equivalents and Prosecution History Estoppel Around the World

However, courts generally adopt “purposive construction,” meaning that patent claims are construed based on how a skilled person would understand them in light of the specification.

Section 186 of the Patent Statute states that patent infringement occurs even if the infringement is “limited to the use of means that are equivalent to the claimed matter.” Most courts apply the US or European function-way-result test for equivalence.

Most courts would hold that a patentee who made narrowing amendments or arguments during examination cannot use DOE to extend the scope of a claim to encompass the excluded subject matter, especially when such amendments or arguments were made to avoid a prior art rejection.

Purposive construction is applied. Principles of purposive construction have been outlined by the Supreme Court which promote adherence to the language of the claims, but state that claim language must also be read in an informed and purposive way.

Confirmed by the Federal Court of Appeal in 2016.

Claim scope is determined by considering the necessary technical features and features equivalent to the necessary technical features. Equivalent features (1) use substantially the same means, perform substantially the same function, and produce substantially the same result as the technical features, and (2) can be contemplated by an ordinarily skilled artisan without inventive labor.

DOE cannot be used to extend the scope of a claim to include (1) a technical solution abandoned in patent granting or invalidation, or (2) features described in the specification or drawings but not in the patent claim.

According to Art. 2 of the Protocol on the Interpretation of Art. 69 EPC, “due account shall be taken of any element which is equivalent to an element specified in the claims.”

Very few court cases have progressed to the final stages of infringement analysis, and these cases have adopted a literal infringement analysis. But, it is possible that courts may consider relying on the principles of DOE and prosecution history estoppel adopted by the US/UK courts.

Applies to an accused product/process that has an element differing from a claim when (1) the differing element is not essential to the patented invention, (2) the accused product/process has the same object and effect as the patented invention, (3) the differing element is an obvious variant of the patented invention, (4) the accused product/process is not in the prior art or obvious in view of it, and (5) no special conditions preclude a finding of infringement, such as applicant having excluded the accused product/process from its scope of protection during examination.

A patentee who made narrowing amendments or arguments during examination cannot use DOE to extend the scope of a claim to include the excluded subject matter.

However, courts generally adopt “purposive construction,” meaning that patent claims are construed based on how a skilled person would understand them in light of the specification.

Prescribed by regulations.

Not prescribed by regulations, but used in court practice.

Applies when (1) the technical idea or principle to solve a problem is identical between the patented invention and the accused product/process, (2) an element recited in the claim accomplishes substantially the same function and effect as a corresponding element in the accused product/process, and (3) the interchangeability of the claimed element with the corresponding element in the accused product/process is obvious to a person skilled in the art.

According to the Supreme Court, DOE cannot be used to extend the scope of a claim if the accused product/process was (1) publicly known or easily conceivable from the prior art, or (2) intentionally excluded from the scope of the claim during examination.

Prescribed by regulations.

Not prescribed by regulations, but used in court practice.

Not prescribed by law, but used in court practice.

Not prescribed by law, but used in court practice. A patentee who made narrowing amendments or arguments during examination cannot use DOE to extend the scope of a claim to include the excluded subject matter. DOE also cannot be used to extend the scope of a claim to include features described in the specification or drawings but not in the patent claim.