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SCOTUS Ruling Shows Consistency Is Key for Invention Descriptions

July 8, 2021, 8:01 AM

In a 5-4 decision writen by Justice Elena Kagan in Minerva Surgical Inc. v. Hologic Inc., the U.S. Supreme Court declined to overturn its assignor estoppel precedent set in 1924 in Westinghouse Elec. & Mfg. Co. v. Formica Insulation Co. that: “If one lawfully conveys to another a patented right, fair dealing should prevent him from derogating from the title he has assigned.”

Instead, the court clarified limitations that uphold the underlying doctrine of fairness and equitable dealing in assignor estoppel.

Assigning a patent implies a guarantee of validity and value. An assignor raising an invalidity defense against the assigned patent “disavows that implied warranty. And he does so in service of regaining access to the invention he has just sold,” according to the decision. The doctrine of assignor estoppel prevents the assignor from guaranteeing validity and then revoking that guarantee.

Questions Raised

Minerva raises an interesting question: Is there still an implied warranty on the validity of any claims having a broader scope than known at the time of assignment?

In the late 1990s, Csaba Truckai invented a device, including a moisture-permeable applicator head (Device I), to treat abnormal uterine bleeding. He later assigned a related patent application, along with any future related applications, to Novacept Inc. U.S. Patent No. 6,816,520 (the ’520 Patent) subsequently issued on Device I. Hologic Inc. later acquired Novacept and its portfolio of patents and applications.

In 2008, the inventor founded Minerva Surgical Inc., where he developed a second abnormal uterine bleeding device but included a moisture-impermeable applicator head (Device II). Hologic applied for and received claims, based on the originally assigned patent, that encompass applicator heads generally, without any limitation regarding moisture permeability. Those claims issued in U.S. Patent No. 9,095,348 (the ’348 Patent).

Hologic sued Minerva for infringing the ’348 Patent. Minerva alleged that the written description of the ’520 patent did not support the claims of the ’348 Patent. Hologic invoked the doctrine of assignor estoppel. The district court agreed that assignor estoppel barred Minerva’s written description defense, and the Federal Circuit affirmed.

The Supreme Court agreed to maintain assignor estoppel. However, the court also noted that the Federal Circuit “applied the doctrine too expansively” (because it failed to recognize the doctrine’s limitations) and held that assignor estoppel may not apply when later claim scope is much broader than contemplated at assignment.

The court vacated and remanded the case to the Federal Circuit to examine the underlying facts of the case. Namely, consistency is key—the Federal Circuit will need to determine whether the claims of the ’348 Patent are materially broader in scope than the claims of the ’520 Patent, and also look at any comments and/or representations made during the prosecution of the ’520 Patent.

While an issued claim scope is fixed, the claim scope in an application is not. The claims of the ’348 Patent did not exist when the inventor assigned his invention.

If the inventor did not warrant the validity of the claims of the ’348 Patent during the prosecution of the ’520 Patent, then assignor estoppel does not apply, and he can challenge the new claims in litigation. The decision stated, “The limits of the assignor’s estoppel go only so far as, and not beyond, what he represented in assigning the patent application.”

Impact on Assignors and Assignees

The practical impact of the Minerva decision will be of paramount importance to both assignors and assignees. When assigning patent rights, an inventor (assignor) should ensure that the scope of the invention being assigned is included in any agreement between the assignor and the assignee.

The scope of any such assignment, and any remarks submitted during prosecution of the patent/application, may govern the outcome of a future dispute.

On the other hand, Minerva limits the extent to which an assignee can assert the doctrine of assignor estoppel. The assignee now has a higher burden of proof to show that any post-assignment claims being asserted are similar, or narrower, in scope than the assigned invention and/or the assignor made statements or representations regarding the assigned patent that are inconsistent with any asserted invalidity defenses.

Chief Justice John Roberts Jr. and Justices Stephen Breyer, Sonia Sotomayor and Brett Kavanaugh joined Justice Kagan. Justice Amy Coney Barrett, joined by Justices Clarence Thomas and Neil Gorsuch, dissented on the ground that the Patent Act of 1952 lacks any explicit, or implicit, incorporation of the doctrine of assignor estoppel, and does not include any exceptions to any invalidity defenses when the inventor is the defendant. Justice Samuel Alito dissented because the court declined to decide whether to overrule Westinghouse.

This column does not necessarily reflect the opinion of The Bureau of National Affairs, Inc. or its owners.

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Author Information

Debodhonyaa Sengupta is a Dentons patent attorney with a doctoral degree in chemistry. She advises clients on matters related to the preparation and prosecution of domestic and international patent applications, patent infringement and validity opinions, and due diligence and freedom-to-operate analyses in the chemical, pharmaceutical, and nanotechnology arts.

Kevin Greenleaf is a Dentons patent attorney specializing in post-grant practice before the Patent Trial and Appeal Board of the Patent and Trademark Office.