The Doctrine of Equivalents

This lesson introduces the doctrine of equivalents, which permits a finding of patent infringement where the accused structure or process does not literally infringe, but differs only insubstantially from the claimed structure or process.

Learning Outcomes

On completion of the lesson, the student will be able to:

1. Define when infringement under the doctrine of equivalents applies.
2. State the “triple identity test.”
3. Explain the "insubstantial differences" test.
4. State the nonobviousness test.
5. Discuss when equivalence is determined.
6. Discuss "file wrapper" estoppel.