Background
Headwater Research LLC is a patent-assertion entity founded in 2008 by Dr. Gregory Raleigh alongside a sister company, ItsOn Inc. Headwater held the patents; ItsOn commercialized the technology. The patents at issue — U.S. Patent No. 8,589,541 and U.S. Patent No. 9,215,613 — both cover background data technologies that manage how mobile devices handle wireless data traffic.
Here is the twist: Verizon was not just a defendant — it was also an investor. Verizon purchased a 10% equity stake in Headwater in 2010 for $1.75 million (and still holds that stake). Between 2015 and 2017, Verizon invested an additional $30 million in ItsOn. Despite this investor relationship, Dr. Raleigh began investigating whether Verizon was infringing Headwater’s patents in 2017, when Verizon’s infringement allegedly started in February 2016. Headwater did not file suit until July 2023 — six years later. When it did sue, it sought the maximum six-year lookback in damages available under 35 U.S.C. § 286, the federal statute of limitations for patent damages.
A jury trial was held in July 2025. The jury found that Verizon had willfully infringed both patents and awarded $175 million in damages. But Judge Gilstrap reserved the equitable defenses of estoppel and waiver for a separate bench trial, which took place on February 4, 2026. On April 22, 2026, he issued this opinion — wiping out the $175 million verdict entirely.
The Court’s Holding
Judge Gilstrap denied equitable estoppel on both theories Verizon raised. He rejected the argument that Verizon’s investment in Headwater, or ItsOn’s representations in investment agreements that no suit was “pending or intended,” gave rise to a reasonable inference that Headwater had acquiesced to infringement. The 2010 investment agreement explicitly permitted Headwater to withhold information that would create a conflict of interest — and investigating patent infringement against an investor creates exactly that conflict. Headwater’s silence was therefore expected, not misleading.
But implied waiver was a different story. The court found that Headwater had full knowledge of Verizon’s infringement as of 2017, flatly rejecting Dr. Raleigh’s trial testimony to the contrary. The court’s reasoning was blunt: at the time Headwater investigated in 2017, it could only recover damages going back to February 2016 — less than two years. By waiting until July 2023 to file, Headwater could claim the full six-year damages window. “As a sophisticated patent-assertion entity, Headwater and Dr. Raleigh knew, or should have known, the obvious advantages of delaying suit.” The court based this credibility determination on firsthand observations of witnesses at both the jury trial and bench trial — something the written record alone cannot capture.
Having found knowledge in 2017, the court then held that Headwater’s six-year silence induced a reasonable belief by Verizon that Headwater had waived enforcement of those patents. The court put the point plainly: “Verizon is entitled to reasonably believe its practice of certain technologies is not encumbered by patent holders lying in wait to bring suit when it most benefits the patent holder.” Then came the opinion’s sharpest passage: “Every law student, early on, learns the equitable concept of unclean hands. Having realized in 2017 that its patents were being infringed, Dr. Raleigh and his corporate entities consciously delayed litigation against Verizon purely to benefit themselves. Six years later, they sued Verizon and asserted that such infringement had been willfully undertaken. This is conduct done with unclean hands.” The result: Headwater cannot enforce the asserted patents against Verizon.
On the SCA Hygiene question — whether the 2017 Supreme Court decision abolishing laches as a bar to patent damages also forecloses implied waiver — Gilstrap said no, on two grounds. First, SCA Hygiene only precludes laches as a defense to damages; here, the court is finding that Headwater has no right to enforce the patents at all, which goes to liability, not damages. Second, implied waiver requires proof of actual inducement of a reasonable belief — a stricter showing than laches — and both SCA Hygiene and its predecessor Petrella v. Metro-Goldwyn-Mayer expressly preserved equitable doctrines more demanding than laches.
Key Takeaways
- Implied waiver survives SCA Hygiene and can defeat an entire infringement case. A patent holder who knowingly delays filing suit to maximize the six-year damages lookback window risks losing the right to enforce entirely — not just having damages reduced. Gilstrap routes around SCA Hygiene by targeting liability rather than damages.
- The six-year damages window is not a timing strategy. Congress’s § 286 lookback period is a limitation on recovery, not an invitation to sit on known infringement. Calculating the optimal filing date based on maximizing the damages period may constitute implied waiver of the right to enforce.
- Knowledge of infringement starts the equitable clock. The critical window is not when suit is filed — it is when the patentee has actual or chargeable knowledge of infringement. Here, investigation in 2017 was sufficient. PAEs with early investigation records face serious implied waiver exposure if they delay filing.
- The investor relationship, while not creating affirmative duties, colors reasonableness. Verizon’s equity stake did not give rise to an implied license or a duty to disclose — but it made Verizon’s belief that Headwater would not run a silent damages clock “all the more reasonable.” Dual investor-target relationships carry strategic and litigation risk on both sides.
- Equitable defenses must be precisely pled. Verizon lost its implied license and acquiescence defenses outright because they appeared only in brief headings and citations rather than as formally asserted defenses. Every equitable defense must be squarely stated in the pleadings and briefing.
Why It Matters
This ruling is a significant check on the business model of patent-assertion entities — companies whose primary activity is licensing and litigating patents rather than making products. PAEs have long exploited the six-year lookback window under § 286, carefully timing lawsuits to capture the maximum possible damages period. Judge Gilstrap has now established that a court can use the doctrine of implied waiver to bar enforcement entirely when a PAE delays suit purely to maximize damages — and the $175 million jury verdict that preceded this ruling makes the stakes crystal clear. A nine-figure verdict can be erased in equity.
The decision also puts an interesting marker on the frontier left open by SCA Hygiene. The Supreme Court shut the laches door in 2017, but expressly left room for other equitable doctrines. Judge Gilstrap, one of the most experienced patent judges in the country, has walked through that opening with implied waiver — applied at the liability level rather than the damages level. Whether the Federal Circuit endorses this approach on appeal will be one of the most-watched patent decisions of 2026 or 2027.