Gideon Korrell Lists 6 Impacts of Estoppel in Patent Infringement
                     GIDEON 
KORRELL LISTS 
6 IMPACTS OF 
ESTOPPEL IN 
PATENT 
INFRINGEMENT
The Federal Circuit’s July 18, 2025 decision in Colibri 
Heart Valve LLC v. Medtronic CoreValve, LLC provides 
a significant lesson on the limits prosecution history 
estoppel places on patent infringement claims under 
the doctrine of equivalents. The court reversed a 
$106 million jury award for Colibri, finding that 
cancelling claims during prosecution prevented 
reclaiming that subject matter later in court.
Charles Gideon Korrell outlines six key impacts of 
estoppel from this case, offering critical insights for 
patent owners and litigators.
1. NARROWED CLAIMS 
LIMIT EQUIVALENTS
When a patent applicant cancels or 
amends claims to overcome examiner 
rejections, this narrowing restricts the 
scope of what can later be claimed as an 
equivalent. In Colibri, the cancelled claim 
covered the accused method’s key 
feature, so estoppel barred extending 
protection to that method.
2. ESTOPPEL 
APPLIES BEYOND 
ASSERTED 
CConLtraAry tIoM a coSmmon misconception, 
estoppel does not only arise from 
amending the exact claim asserted in 
litigation. Here, the cancelled claim was 
closely related to the asserted claim, and 
the court found estoppel applied because 
the cancelled claim’s subject matter was 
effectively surrendered.
3. LITIGATION 
ARGUMENTS 
CAN In arguing equivalence, Colibri relied on 
BACKFIRE “basic physics,” stating opposing forces 
(pushing and retracting) act together. 
This unintentionally confirmed that the 
accused method was encompassed by 
the cancelled claim, strengthening the 
estoppel effect.
4. EXCEPTIONS 
MUST BE ARGUED
Patent owners can sometimes avoid estoppel by 
showing exceptions such as unforeseeability of the 
accused equivalent, tangentiality of the 
amendment, or inadequate description. Colibri did 
not present such arguments, so estoppel stood 
without rebuttal.
5. 
PROSECUTION 
STRATEGY 
KMorrell emphasizes the importance of prAoseTcutTionE stRrateSgy. Rather than 
cancelling key claims that cover 
important alternative embodiments, 
patent owners should consider filing 
continuation applications or other 
measures to maintain options.
6. PROSECUTION 
HISTORY DEFINES 
PATENT SCOPE
The court reaffirmed that the prosecution 
record provides public notice of claim scope 
boundaries. Patentees cannot reclaim 
through litigation what they gave up during 
prosecution, preserving legal certainty for 
competitors and the public.
BACKGROUND 
AND CASE 
SUMMARY
The Colibri patent described a method to implant a 
collapsible heart valve featuring a “do-over” step—allowing 
partial deployment and repositioning if needed. Two 
independent claims originally covered this step: one by 
pushing the valve out of the delivery sheath, another by 
retracting the sheath to expose the valve. The retraction 
claim was rejected by the examiner for lack of written 
description and was cancelled.
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