# Pannu v. Iolab: The Three-Part Test for Who Counts as a Joint Inventor

> The Federal Circuit set out the durable standard for joint inventorship and confirmed that misjoinder or nonjoinder is not automatic invalidity, because the patentee must be given a chance to correct under Section 256.

Topic: Patents  |  Author: Lidiia Levitska  |  Source: Intellectual Property Law (outsideipcounsel.com)
Canonical: https://outsideipcounsel.com/blog/pannu-v-iolab-joint-inventor-test-correction-section-256/


*Pannu v. Iolab Corp.*, 155 F.3d 1344, Nos. 97-1466, 97-1501 (Fed. Cir. Aug. 6, 1998), supplies the analytical spine of modern joint-inventorship law. While *Ethicon* showed what happens when a co-inventor is left off a patent, *Pannu* answered the prior question: what does it actually take to be a joint inventor in the first place? The court articulated a three-factor test that has been quoted in countless opinions since, and recently invoked by the USPTO in its guidance on AI-assisted inventions. *Pannu* also clarified the relationship between inventorship error and validity: a patent with the wrong inventors is not automatically void, because 35 U.S.C. § 256 gives the patentee a chance to correct the error (subject, under the pre-AIA statute the court applied, to the absence of deceptive intent).

## At a glance

- **Case:** *Pannu v. Iolab Corp.*, 155 F.3d 1344 (Fed. Cir. 1998)
- **Docket:** Nos. 97-1466, 97-1501; decided August 6, 1998
- **Court:** U.S. Court of Appeals for the Federal Circuit
- **Panel:** Chief Judge Mayer, Judge Lourie, Judge Rader
- **Patent:** U.S. Reissue Patent No. 32,525, an improved intraocular lens designed to reduce tissue snagging during cataract implantation
- **Parties:** Dr. Jaswant S. Pannu (named inventor/plaintiff); Iolab Corp. (accused infringer)
- **Holdings:** (1) the three-part test for joint inventorship (155 F.3d at 1351); (2) misjoinder/nonjoinder is not an automatic invalidity ground, because the patentee must be given an opportunity to correct under § 256
- **Status:** Vacated and remanded in relevant part for the district court to apply the correct framework

## The dispute over a co-inventor

Dr. Jaswant Pannu held Reissue Patent No. 32,525 covering an improved intraocular lens (an artificial lens implanted after cataract surgery) engineered so that its supporting elements would not snag delicate eye tissue during insertion. Pannu sued Iolab for infringement. At trial, evidence emerged that Dr. William Link, then president of lens manufacturer Heyer-Schulte, had suggested that Pannu's lens could be made from a single piece of plastic, yet Link was not named on the patent. Iolab argued that the omission rendered the patent invalid for improper inventorship.

The district court's handling of that argument is what brought the case up on appeal. Before the case went to the jury, the court granted Pannu judgment as a matter of law on the inventorship defense, reasoning that there was no evidence Link was ever the sole inventor and that, even if Link were a co-inventor, Iolab had not shown Pannu acted in bad faith, so the error would be correctable under § 256. The jury then found two of four accused lenses infringing and awarded Pannu $670,667.47. The Federal Circuit held that the inventorship defense should have reached the jury and used the appeal to lay down the proper two-step framework: first decide whether the omitted person is actually a joint inventor, and only then ask whether the resulting error is correctable.

## The three-part joint-inventorship test

The court's most enduring contribution is its statement of what makes someone a joint inventor. Conception is the touchstone, but not every contribution to a project rises to the level of co-invention. To qualify, a putative inventor must:

1. **Contribute in some significant manner to the conception or reduction to practice of the invention.**
2. **Make a contribution to the claimed invention that is not insignificant in quality, when that contribution is measured against the dimension of the full invention.**
3. **Do more than merely explain to the real inventors well-known concepts and/or the current state of the art.**

The test deliberately filters out two categories of participants who often feel they deserve credit but legally do not: those who supply only ordinary skill or routine assistance in reducing an idea to practice, and those who merely convey the existing state of the art or well-understood principles. A contribution must be both qualitatively significant relative to the whole invention and genuinely inventive rather than instructional. The framework's flexibility ("measured against the dimension of the full invention") is precisely what has made it adaptable, and it is why the USPTO turned to the *Pannu* factors when assessing whether a natural person made a significant enough contribution to an AI-assisted invention to be a proper inventor.

## Section 256 and the deceptive-intent gate

The second holding addresses what follows once a court finds the named inventors wrong. Improper inventorship, naming too many inventors (misjoinder) or too few (nonjoinder), is a condition of patentability under 35 U.S.C. § 102(f) (pre-AIA). But the Federal Circuit emphasized that such an error does not automatically doom the patent, because Congress provided a cure. The version of § 256 in force when *Pannu* was decided allowed correction where, "through error," a person was named who should not have been, or where "through error an inventor is not named in an issued patent and such error arose without any deceptive intention on his part." For nonjoinder, the deceptive-intent inquiry ran to the omitted inventor: correction was available "upon a showing that the error occurred without any deceptive intent on the part of the unnamed inventor."

The court therefore prescribed a sequence. First, the district court determines whether there is clear and convincing proof that the alleged omitted (or wrongly named) person is in fact a co-inventor under the three-part test. If so, the patentee must be given an opportunity to invoke § 256 and correct the inventorship. On that question the court observed that while lack of deceptive intent "may be hard for a patentee to prove when it claims relief under the statute, good faith is presumed in the absence of a persuasive showing of deceptive intent." Note where the clear-and-convincing burden sits: it governs proof of co-inventorship, not proof of deception. If the patentee does not claim relief under § 256, or the error cannot be corrected, the patent must be held invalid under § 102(f). Because the district court had collapsed these inquiries, the Federal Circuit vacated and remanded for proper application of the framework.

One point of currency: the America Invents Act (Pub. L. 112-29, effective September 16, 2012) struck the "without any deceptive intention" language from § 256 and repealed § 102(f) for patents governed by the AIA. *Pannu*'s three-factor test remains good law and is quoted constantly; its deceptive-intent gloss describes the pre-AIA statute.

## Open questions

*Pannu* gives a test but not a formula, and its qualitative language leaves recurring uncertainty. How "significant" a contribution must be, and how courts should weigh it "against the dimension of the full invention," are intensely fact-bound questions that continue to divide litigants, particularly for collaborators who contribute to some claims but not others, or whose input straddles the line between inventive insight and skilled execution. The deceptive-intent standard has its own afterlife: the AIA repealed § 102(f) and deleted the "deceptive intention" language from § 256 for patents it governs, so for AIA patents the gate *Pannu* described no longer appears in the statute, and the interaction between inventorship errors and inequitable-conduct doctrine after *Therasense* remains contested. Finally, the application of the *Pannu* factors to machine-assisted invention (where the "contributor" is a tool rather than a person) is only beginning to be worked out.

## Implications

- **Use the three factors as a checklist.** Before filing, evaluate each contributor against significance of contribution, quality relative to the whole invention, and whether they went beyond explaining known art.
- **Distinguish inventors from helpers.** Supplying ordinary skill, routine reduction to practice, or a recital of the state of the art does not make someone a joint inventor.
- **Inventorship errors are usually fixable.** Misjoinder and nonjoinder do not automatically invalidate a patent; § 256 permits correction, and the AIA removed the deceptive-intent condition for patents it governs.
- **Challengers must prove co-inventorship by clear and convincing evidence.** That is where the heavy burden sits in *Pannu*. Under the pre-AIA statute, good faith was then presumed absent a persuasive showing of deceptive intent, but a patent still failed if the patentee never sought correction.
- **Document contributions contemporaneously.** Inventor declarations, lab records, and contribution logs make both the *Pannu* analysis and any later § 256 correction far more defensible.

## Frequently asked questions

**What is the *Pannu* test?**
It is the Federal Circuit's three-part standard for joint inventorship: a co-inventor must (1) contribute significantly to conception or reduction to practice, (2) make a contribution not insignificant in quality measured against the full invention, and (3) do more than explain well-known concepts or the state of the art.

**Does naming the wrong inventors automatically invalidate a patent?**
No. Under *Pannu*, a challenger must first prove co-inventorship by clear and convincing evidence, and the patentee must then be given a chance to correct the error under 35 U.S.C. § 256. The pre-AIA statute conditioned correction of nonjoinder on the absence of deceptive intent by the unnamed inventor, with good faith presumed; the America Invents Act removed that condition in 2012.

**Why does *Pannu* matter for AI-assisted inventions?**
The USPTO has invoked the *Pannu* factors to assess whether a natural person contributed enough to an AI-assisted invention to be a proper named inventor: a person must make a significant contribution under these factors, not merely oversee or prompt an AI system.

## Authorities and sources

- Federal Circuit opinion, *Pannu v. Iolab Corp.*, 155 F.3d 1344 (Fed. Cir. 1998), full text (BitLaw): https://www.bitlaw.com/source/cases/patent/Pannu.html
- Leagle, *Pannu v. Iolab Corp.*, 155 F.3d 1344: https://www.leagle.com/decision/19981499155f3d134411349
- 35 U.S.C. § 256 (correction of named inventor), Legal Information Institute: https://www.law.cornell.edu/uscode/text/35/256
- USPTO, "Inventorship Guidance for AI-Assisted Inventions," 89 Fed. Reg. 10043 (Feb. 13, 2024) (applying the *Pannu* factors), govinfo: https://www.govinfo.gov/content/pkg/FR-2024-02-13/pdf/2024-02623.pdf