## Facts

- Wilson owned U.S. Patent No. 4,560,168, directed to a golf-ball dimple pattern that divides the ball surface into geometric regions and places dimples so that no dimple center lies on specified great-circle boundary lines.
- Wilson sued Dunlop Slazenger Corp. and David Geoffrey & Associates (DGA), the exclusive U.S. distributor of one accused ball, alleging infringement by certain Dunlop/Slazenger golf balls.
- The accused balls used a different dimple layout in which some dimples intersected great-circle lines that Wilson’s claims required to remain free of dimple centers.
- Dunlop contended that, given prior art golf-ball patterns, extending Wilson’s claims to cover the accused layouts under the doctrine of equivalents would improperly capture what was already disclosed or suggested in the prior art.
- In the Dunlop action, a jury returned special verdicts finding the asserted claims valid and willfully infringed, and judgment was entered against Dunlop.
- In the DGA action, the court entered summary judgment of liability for Wilson based on collateral estoppel, reasoning that DGA’s interests were effectively represented in the Dunlop action.
- Dunlop and DGA appealed, and the Federal Circuit consolidated the appeals.

## Issues

1. Whether Dunlop’s post-trial motion for judgment notwithstanding the verdict (Rule 50(b) motion) was timely and sufficiently supported by an earlier directed-verdict motion.
2. Whether the doctrine of equivalents can support infringement when the equivalence needed to reach the accused product would also encompass prior art, and what method should be used to test that limitation.
3. Whether summary judgment against DGA based on collateral estoppel was proper.

## Decision

- The Federal Circuit held Dunlop’s Rule 50(b) motion was timely and procedurally adequate; the trial court erred in treating it as barred.
- The court reversed the infringement judgment, holding there was no infringement under the doctrine of equivalents because the necessary range of equivalents would cover prior art.
- The court applied a “hypothetical claim” analysis and concluded that any hypothetical claim broad enough to literally cover the accused balls would have been unpatentable over the prior art.
- Because the Dunlop liability judgment was reversed, the collateral-estoppel-based summary judgment against DGA could not stand; the court reversed in part and vacated in part the judgment against DGA.

## Legal Principles

- The doctrine of equivalents cannot extend a patent’s scope to cover subject matter that would have been unpatentable over the prior art.
- Prior art limits the range of permissible equivalents; there is no infringement where the required scope of equivalence would “ensnare” the prior art.
- A court may assess ensnarement by positing a hypothetical claim that literally covers the accused product and then asking whether that hypothetical claim would have been patentable over the prior art.
- The patentee bears the burden to show that the asserted range of equivalents, as tested through the hypothetical claim approach, does not capture the prior art.
- Collateral estoppel premised on a prior liability determination fails when the underlying liability judgment is reversed.

## Conclusion

The Federal Circuit reversed liability for infringement because Wilson’s doctrine-of-equivalents theory required a scope that would have covered prior art, and it endorsed a hypothetical-claim patentability inquiry—borne by the patentee—to police that limit; the related collateral-estoppel judgment against the distributor was set aside once the manufacturer’s liability judgment fell.


Wilson Sporting Goods Co. v. David Geoffrey & Assocs., 904 F.2d 677 (Fed. Cir. 1990)