Estoppel arises from claim amendments narrowing scope for reasons of patentability and from arguments distinguishing prior art. Festo creates a presumption of complete surrender for the territory between the original and amended claim.
The presumption is rebuttable in limited circumstances.
Alternative Names:
File Wrapper Estoppel|Prosecution Estoppel
Why it Matters?
The Festo presumption places the burden on the patentee to establish that the equivalent was unforeseeable, tangentially related to the amendment, or otherwise beyond reasonable expectation, which is a demanding showing that fails in most cases. Argument-based estoppel operates without any amendment, arising from statements distinguishing prior art, which makes the complete prosecution file essential reading rather than only the amendments.
Frequently Confused with
Related terms
Frequently asked questions
What does the Festo presumption require?
Does estoppel require an amendment?
