## Facts

- Insituform owned U.S. Patent No. 4,366,012, claiming a method for repairing underground pipelines by impregnating a tube liner with resin using vacuum applied through windows cut in an outer impermeable layer.
- Claim 1, as amended during prosecution, required using a single vacuum cup applied to a window, drawing resin under vacuum, then moving the cup “downstream” to successive windows while sealing prior windows.
- The patent applicant amended claim 1 to add the single-cup, move-along-windows limitation after a rejection over prior art and argued that the amended approach solved problems associated with suction applied from an end source.
- Insituform sued CAT Contracting and related entities for infringement; the accused methods used vacuum-cup arrangements during resin impregnation and were litigated through multiple phases, including a prior appeal and remand proceedings.
- The district court found infringement and awarded damages, found willful infringement by CAT and Firstliner, joined Insituform (Netherlands) B.V. as a plaintiff and Giulio Catallo as a defendant, and declined to impose alter-ego liability on Kanal Sanierung Hans Mueller GmbH & Co. KG (KS).

## Issues

1. Whether prosecution-history estoppel barred Insituform from asserting that multiple-cup vacuum processes infringed claim 1 under the doctrine of equivalents.
2. Whether the evidence supported the district court’s infringement findings against CAT, Firstliner, Catallo, and Michigan Sewer Construction Company.
3. Whether the district court’s willfulness finding against CAT and Firstliner was legally and factually supportable.
4. Whether joinder of Insituform (Netherlands) B.V. as a plaintiff and Catallo as a defendant was proper.
5. Whether KS should be held vicariously liable for induced infringement under an alter-ego theory.

## Decision

- The Federal Circuit affirmed the judgment of infringement against CAT, Firstliner, Catallo, and Michigan Sewer Construction Company.
- The court held that the prosecution history limited the scope available under the doctrine of equivalents because claim 1 was narrowed for patentability to include the single, movable vacuum-cup configuration.
- The court vacated the finding of willful infringement as to CAT and Firstliner and remanded for further proceedings on willfulness.
- The court affirmed joinder of Insituform (Netherlands) B.V. as a plaintiff and Catallo as a defendant.
- The court affirmed the refusal to impose alter-ego (veil-piercing) liability on KS.

## Legal Principles

- A narrowing amendment made for reasons related to patentability can trigger prosecution-history estoppel, restricting doctrine-of-equivalents arguments for surrendered subject matter.
- Prosecution statements and amendments may amount to a clear and unmistakable surrender that prevents recapture of what was given up to obtain allowance.
- Infringement findings, including equivalence determinations within the bounds left by estoppel, are upheld absent clear error.
- Willfulness requires a supported analysis of whether the accused infringer’s defenses and positions were objectively reasonable under governing law; if the analysis is incomplete, vacatur and remand are appropriate.
- Joinder of entities with relevant patent interests or involvement in accused conduct is permitted when it serves complete adjudication and preclusion goals and is within the trial court’s discretion.
- Alter-ego liability requires proof sufficient to disregard corporate separateness, including domination or misuse of the corporate form; absent such proof, veil-piercing is denied.

## Conclusion

The Federal Circuit left the infringement judgment intact but limited the patentee’s doctrine-of-equivalents reach through prosecution-history estoppel based on claim-narrowing amendments and arguments, vacated and remanded the willfulness finding for further analysis, and affirmed joinder and the denial of alter-ego liability.


Insituform Technologies, Inc. v. CAT Contracting, Inc., 385 F.3d 1360 (Fed. Cir. 2004)