Doctrine of Equivalents
To understand Doctrine of Equivalents, we need to review what Patent Infringement means. A party who commercializes a product without acquiring a license from a patent holder is liable to be accused of a patent infringement.
There are two kinds of patent infringement, namely Direct Infringement & Indirect Infringement.
In Direct Infringement, the infringing device/system/process/method should fall within the literal scope of a patent claim(s). Whereas in Doctrine of Equivalents (DOE) which is one kind of an Indirect Infringement, the infringing device need not literally fall within the scope of the claim but must be equivalent to the claimed invention. When we say equivalent, it means that the device or process should perform substantially the same function, in substantially the same way, to achieve substantially the same result as that of the claimed invention. This is also called as function/way/result test.
The reason for this rule is to keep an infringer from taking the advantage of a protected invention by only making minor changes to the claim’s teaching and yielding a similar outcome.
This rule is followed in most countries with some minor changes.
What is an “All elements” test?
According to the “all element” test, the doctrine of equivalents should be tested for all the elements of a claim and not the claimed invention on the whole. Therefore, it becomes necessary to show the accused product performing similar functionalities of all the elements of a claim. Something is viewed as equivalent if there is only an insubstantial change between the accused device and the patent claim. However, this “all element” rule poses a limitation to the doctrine of equivalents.
Similarly, any existence of an element in prior art automatically prevents the patent owner from claiming equivalency to incorporate that element in the alleged device.
DOE also includes File History Estoppels. One being Amendment-based and the other Argument-based. In Amendment-based Estoppel, amendments made during the prosecution i.e. from the original claim to the amended allowed claim creates an assumption that all the scope in-between is given-up. Whereas, in Argument-based Estoppel, the applicant clearly gives-in to the scope of the claims. There are no presumptions done in this case.