Patents

Ethicon v. U.S. Surgical: One Omitted Co-Inventor Can Sink an Infringement Suit

A co-inventor of even a single claim becomes a co-owner of the whole patent — and the Federal Circuit let that overlooked inventor license the accused infringer and dismantle the case.

May 26, 2025
Surgeons using endoscopic instruments in an operating room
An electronics technician who helped design a trocar's safety mechanism turned out to co-own the entire patent — and licensed the defendant. Shutterstock
Educational content, not legal advice. This article explains general legal concepts. It does not create an attorney–client relationship. For your specific situation, consult a licensed attorney.

Ethicon, Inc. v. United States Surgical Corp., 135 F.3d 1456, No. 97-1269 (Fed. Cir. Feb. 3, 1998), is the case that makes patent owners lose sleep over the people they did not name. The Federal Circuit held that a person who contributes to the conception of even one claim of a patent is a joint inventor of that patent — and, absent an agreement otherwise, a co-owner of the entire patent with full rights to exploit and license it. The accused infringer in Ethicon found the overlooked co-inventor, took a retroactive license from him, and used that license to force dismissal of the suit. The plaintiff’s own incomplete inventorship became the defendant’s complete defense.

At a glance

  • Case: Ethicon, Inc. v. United States Surgical Corp., 135 F.3d 1456 (Fed. Cir. 1998)
  • Docket: No. 97-1269; decided February 3, 1998
  • Court: U.S. Court of Appeals for the Federal Circuit
  • Panel: Judge Newman (dissenting in part), Senior Judge Skelton, Judge Rader (author)
  • Patent: U.S. Patent No. 4,535,773 — a trocar with a safety mechanism for endoscopic surgery
  • Named inventor: Dr. InBae Yoon; omitted contributor: Young Jae Choi, an electronics technician
  • Claims at issue for co-inventorship: claims 33 and 47
  • Holding: Choi was a joint inventor of at least one claim, making him a co-owner of the entire patent; his license to U.S. Surgical, and his refusal to join as a plaintiff, required dismissal
  • Status: District court judgment affirmed in relevant part

How a technician became a co-owner

Dr. InBae Yoon, a surgeon and prolific inventor, conceived of an improved trocar — the instrument used to puncture the abdominal wall in endoscopic surgery — equipped with a safety device to prevent the blade from injuring internal organs after it passes through the wall. To develop the electronics, Yoon collaborated for a period with Young Jae Choi, a technician with expertise in electronic devices. The collaboration ended, and Yoon alone was named as the inventor on the resulting ‘773 patent. Choi’s name appeared nowhere on it.

Years later, Ethicon (Yoon’s exclusive licensee) sued U.S. Surgical for infringing the ‘773 patent. During pretrial investigation, U.S. Surgical located Choi and concluded that he had contributed to the conception of the claimed safety trocar. U.S. Surgical then obtained from Choi a retroactive, nonexclusive license to whatever rights he held in the ‘773 patent. Armed with that license, U.S. Surgical moved to correct inventorship to add Choi under 35 U.S.C. § 256, and then to dismiss the suit on the theory that Choi — now a co-owner — had both licensed the defendant and declined to consent to the litigation.

The conception inquiry: claims 33 and 47

The court framed joint inventorship around conception, “the touchstone of inventorship.” A joint inventor need not contribute to every claim; a contribution to the conception of a single claim is enough to confer the status of co-inventor of the patent as a whole. Nor must each collaborator contribute equally or work side by side at every step. What is required is a contribution to conception that is not insignificant when measured against the full invention, and something more than merely explaining the state of the art or following another’s instructions.

Applying that standard, the district court found, and the Federal Circuit affirmed, that Choi contributed to the conception of subject matter in two claims. As to claim 33, Choi contributed to the structure that allowed the safety mechanism to operate; as to claim 47, he contributed to the means by which the device sensed the absence of tissue and triggered the safety. The court rejected Yoon’s effort to characterize Choi’s role as mere technical implementation of Yoon’s own ideas. Because Choi’s contribution reached the conception of at least one claim, he qualified as a joint inventor of the entire patent. Judge Newman, in partial dissent, would have scrutinized more skeptically whether Choi’s contributions rose to the level of joint conception rather than ordinary skilled assistance.

The consequence of co-inventorship is the heart of the decision. Under 35 U.S.C. § 262, in the absence of an agreement to the contrary, “each of the joint owners of a patent may make, use, offer to sell, or sell the patented invention within the United States … without the consent of and without accounting to the other owners.” Each co-owner thus holds an undivided interest in the whole and may independently license third parties. A co-owner who licenses an accused infringer immunizes that infringer to the extent of the license.

That rule collided with another: all co-owners of a patent must ordinarily join as plaintiffs in an infringement suit, and one co-owner cannot be involuntarily forced to join in another’s litigation. Choi had licensed U.S. Surgical and would not consent to sue it. Because Ethicon’s complaint depended on Yoon’s rights alone and lacked the participation of co-owner Choi — who had, in effect, granted the defendant permission to practice the invention — the suit could not proceed. The Federal Circuit affirmed dismissal. The painful lesson: a single uncredited contributor, located years later by an adversary, can hold a veto over the entire enforcement effort.

Open questions

Ethicon sharpened the doctrine but left practical tensions. The opinion does not fully resolve how courts should distinguish a genuine contribution to conception from the skilled-but-ordinary assistance that every inventor relies upon — the line Judge Newman pressed in dissent, and one that recurs in modern disputes over engineers, consultants, and now AI tools. It also leaves the all-substantial-rights and standing analysis sensitive to the precise scope of a co-owner’s later license: how “retroactive” a license may be, and whether such a license can defeat claims for past damages, continues to be litigated. And because the result turns on the default rule of § 262, it leaves wide room for private ordering — but only for parties who anticipate the problem and contract around it in advance.

Implications

  • Inventorship is an enforcement issue, not a formality. Getting the inventor list wrong can hand an accused infringer a co-owner who licenses the defendant and refuses to join the suit, ending the case.
  • A contribution to one claim confers ownership of the whole patent. Co-inventor status is binary at the patent level; even a minor-but-significant contribution to a single claim makes someone a full co-owner absent an assignment.
  • Secure assignments from every contributor. Anyone who may have contributed to conception — employees, consultants, collaborators, technicians — should sign a present assignment before, not after, the patent issues.
  • Diligence the inventorship of patents you acquire or assert. Buyers, licensees, and litigation counsel should investigate whether unnamed contributors exist, because they can later be enlisted by an opponent.
  • Co-ownership without a governing agreement is dangerous. Section 262 lets any co-owner license freely and bars suit without all owners; joint development should be papered with exclusive grant-backs or covenants to sue.

Frequently asked questions

Did contributing to just one claim really make Choi a co-owner of the entire patent? Yes. The Federal Circuit held that conception of the subject matter of a single claim is enough to make a person a joint inventor of the patent, and a joint inventor is, by default, a co-owner of the whole patent with an undivided interest in all of it.

How did a license from the omitted inventor defeat the lawsuit? Under 35 U.S.C. § 262, each co-owner may independently license others. Choi licensed U.S. Surgical, immunizing it, and then declined to join the suit. Because all co-owners must ordinarily be plaintiffs and none can be forced to sue, Ethicon’s case had to be dismissed.

Could the patent owner have avoided this outcome? Largely, yes — through correct inventorship and, critically, by obtaining a written assignment from every contributor. An assignment from Choi would have consolidated title and eliminated his ability to license the defendant or block the litigation.

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