PTAB and District Court Litigation Strategies Post-Kroy v. Groupon

The Federal Circuit’s decision in Kroy v. Groupon has set the stage for new strategies in patent litigation. This episode explores staggered claim assertion strategies, discusses key distinctions from prior rulings, and shares practical tips for navigating the complexities of post-Kroy litigation. Insights from Angela highlight its unique impact in technology-driven sectors.

Published OnMarch 20, 2025

Chapter 1

The Federal Circuit’s Decision in Kroy v. Groupon

Erick
Welcome to this episode of the PTAB Podcast. As always, the views and opinions expressed in this podcast do not necessarily represent those of Brown Rudnick. This podcast is presented for informational and educational purposes only.
Erick
I am again here with my friend and fellow patent litigation attorney , Dr. Angela Liu. Thanks for joining me today, Angela!
Dr. Angela Liu
It's great to be here with you, Erick! Let's talk some PTAB!
Erick
Alright, Angela, let's dive into this Federal Circuit decision—_Kroy v. Groupon_. This one really shakes things up when it comes to how PTAB inter partes reviews interact with district court cases. The court's holding on estoppel? Kind of a game changer.
Dr. Angela Liu
Absolutely, it's a significant shift. The court essentially said that just because the PTAB invalidates certain claims, it doesn’t mean you’re barred from asserting other claims in district court—even if those other claims are pretty similar on the surface. That's huge for patent holders, especially smaller players.
Erick
Right, and it dismantles that assumption of a one-size-fits-all estoppel between the PTAB and district courts. They’re operating on different evidentiary standards. PTAB uses the preponderance of the evidence, while in district courts, it’s gotta be clear and convincing proof.
Dr. Angela Liu
Exactly. And let’s not forget how this decision contrasts with previous rulings like _XY_ and _Ohio Willow Wood_. Those cases applied estoppel much more rigidly, but here, the Federal Circuit carved out a careful distinction. They’re saying that unless you’re dealing with the exact same claims, estoppel just... doesn’t stick.
Erick
This opens the door for some crafty strategies, doesn't it? Like holding back certain claims just in case your strongest ones get knocked out at the PTAB. You can essentially keep a few aces up your sleeve for later district court proceedings.
Dr. Angela Liu
Definitely. It’s what I’d call the staggered assertion strategy—assert the broadest, strongest claims first, get discovery rolling, and, if need be, pivot to those backup claims. Smaller patent owners especially stand to benefit, since they can adapt as the litigation unfolds.
Erick
And the beauty of this strategy is—it’s almost like playing legal chess. You’re forcing the other side to change tactics mid-game. Imagine losing at the PTAB with Tier 1 claims and then surprising everyone with those Tier 2 fallbacks in district court.
Dr. Angela Liu
It’s a fantastic way to maintain leverage. But, Erick, I think it also promotes smarter drafting on the front end. Patent owners need to carefully differentiate their claims to create those fallback options—without making them so similar that they go down together.
Erick
Right, right. And this ties directly into what we see in infringement complaints. File that subset of your best claims first, leave gaps, and keep something in reserve for after the PTAB decision drops. It’s—it’s just smart litigation.
Dr. Angela Liu
And don’t forget the broader landscape here. This decision recalibrates how patent owners manage their claim portfolios and navigate this whole dual-track litigation environment. It’s not just about surviving PTAB; it’s about thriving in district court too.
Erick
Exactly. And this ruling makes that flexibility possible.

Chapter 2

Key Takeaways from Kroy

Erick
Alright, Angela, let’s continue from where we left off. This flexibility to sidestep estoppel isn’t just a game-changer—it’s an open invitation for patent owners to really strategize. What’s your take on how this might reshape courtroom tactics moving forward?
Dr. Angela Liu
Totally. The Federal Circuit here recognizes that these two forums aren’t interchangeable. With PTAB using the preponderance-of-the-evidence standard, and district courts requiring clear and convincing proof, they’re basically acknowledging the gap in how invalidity is treated.
Erick
Right. So now, claims that weren’t explicitly invalidated by the PTAB can have another life in district court. Even if they’re nearly identical on paper.
Dr. Angela Liu
Exactly. And that’s a critical distinction. This decision gives patent owners some real breathing room to regroup—and even counterattack—after PTAB proceedings.
Erick
It’s a game changer. And the way it sidesteps those older rulings from XY and Ohio Willow Wood? That’s important too. Those cases leaned much more heavily on estoppel because they involved the exact same claims being targeted over and over.
Dr. Angela Liu
That’s where Kroy adds all this nuance. They’re saying, “Look, if the claim isn’t identical and it wasn’t fully adjudicated, we’re not applying estoppel here.” It’s a sharp pivot from how courts used to interpret those earlier cases.
Erick
Okay, but let’s talk strategies, because Kroy isn’t just theoretical—it demands some real shifts. This idea of holding back claims in reserve during initial filings? For patent owners, that’s practically revolutionary.
Dr. Angela Liu
I know, right? It’s what we’ve been calling the strategic “hold-back” of claims. You start with your broadest, strongest claims—the ones most likely to grab attention in court—and hold back a tier of slightly narrower ones, just in case.
Erick
And you know, the brilliance lies in how flexible this makes your case. If Tier 1 claims fall at PTAB, you’ve still got ammunition. It’s almost like—like a backup generator kicking in when the power goes out.
Dr. Angela Liu
Such a great analogy. It’s just smart litigation planning. But—this only works well if those fallback claims are crafted with precision. They should be immaterially different—not so similar that they risk getting knocked out alongside the primary claims.
Erick
Exactly. And this has implications not just for litigators but for patent drafting itself. Differentiating claims effectively at the prosecution stage is key. You’re building in flexibility for future litigation without creating liability traps.
Dr. Angela Liu
And it’s not just about differentiation. It’s also about timing. Staggering the assertion of these claims across various phases—PTAB first, district court later—maximizes leverage and keeps those fallback claims available for when you really need them.
Erick
It’s tactical, no doubt. But let’s not forget, this strategy also forces your opponent into an uncomfortable position. It’s like—you’re narrowing the road they can take while keeping your own options wide open.
Dr. Angela Liu
Absolutely. That kind of control is invaluable, especially for smaller patent owners who don’t have the resources to absorb major losses upfront. Kroy effectively gives them a second chance on that battlefield.
Erick
All while fundamentally reshaping how these dual forums interact. Amazing stuff.

Chapter 3

Staggered Claim Assertion Strategies

Erick
Absolutely, Angela. That second chance you mentioned is such a lifeline for smaller patent owners. Speaking of strategy, this staggered claim approach you brought up—it’s gotten a lot of buzz lately. Can you break down why it’s proving so effective?
Dr. Angela Liu
Well, it all comes down to flexibility. By using a tiered structure for your claims, you’re able to create multiple layers of defense. Start with the broadest claims, hold back some narrower ones, and adapt as the litigation unfolds. It’s a dynamic way to stay one step ahead of your opponent.
Erick
Right. And this isn’t just about legal theory—it’s tactical as hell. Crafting your initial complaints with gaps or reserves gives you room to maneuver if the PTAB comes down hard on your primary claims. It’s like—you’re setting the stage for a second act instead of putting all your cards on the table at once.
Dr. Angela Liu
Exactly. Take a real-world example: I had a client whose Tier 1 claims got invalidated at the PTAB. But because we held back the Tier 2 claims—those immaterially different versions—we were able to assert them in district court and ultimately settle on much more favorable terms. It was, I have to say, a textbook case of this strategy in action.
Erick
Textbook, indeed. And it’s all built on the principle of maintaining leverage. But—and this is where I see the cracks sometimes—it’s critical to address the burden of proof early on. District courts require clear and convincing evidence for invalidity, which is a far cry from the PTAB’s preponderance standard.
Dr. Angela Liu
That’s true. And that difference creates opportunities. Let’s say your first set of claims didn’t make it through—I mean, the PTAB invalidated them—but the fallback claims? Those have a whole new lease on life in district court because of that higher evidentiary bar.
Erick
But it’s not just about the claims themselves, right? You’ve gotta think about how you’re setting up your case for success. Like reserving those fallback claims—not to mention crafting them so they’re strong enough to stand alone but distinct enough to avoid collective invalidation.
Dr. Angela Liu
Absolutely. It’s not just clever lawyering. It’s smart patent drafting. Differentiation at the prosecution stage lets you create this, well, safety net. And once you’re in litigation, staggered assertion means you’re controlling the pace and structure of the fight.
Erick
And it forces your opponent off balance. They don’t know what’s coming next, and they’ve gotta stretch their resources across PTAB and district court battles. That kind of disruption? It’s priceless for smaller patent holders who don’t have unlimited litigation budgets.
Dr. Angela Liu
It really is. This decision empowers those smaller players to navigate dual-track litigation without being outmaneuvered by sheer capital. Patent law is all about leverage—and Kroy just gave it back to the little guy in a huge way.
Erick
Couldn’t agree more. It’s strategic layered defenses in action, and honestly, it’s a brilliant way to stay ahead of the game.

Chapter 4

Recommendations

Erick
Angela, speaking of those layered defenses you masterfully outlined earlier, let’s zoom in on one of their core principles—tiering your claim portfolio. It’s a straightforward idea in theory but a game-changer when executed well. What’s your perspective on why this approach is so impactful?
Dr. Angela Liu
It really comes down to maximizing flexibility. You start with those Tier 1 claims—broad, strong, foundational claims that set the tone for your case and attract early attention. But Tier 2 claims? Those are your safety net. They’re immaterially different but strategically held back for later phases of litigation.
Erick
And that’s where the genius lies. It’s like a two-pronged attack. The Tier 1 claims draw all the fire early on, and then, if needed, you pivot to the Tier 2 claims. Holding those back essentially gives you options if the PTAB comes for the big guns first.
Dr. Angela Liu
Exactly. And the beauty of it is, you don’t lose momentum. Pair this with staggered complaints, and you’ve got a multi-phase strategy that keeps opponents guessing. It transforms litigation into a moving target.
Erick
Right, which brings us to the next point—drafting complaints with intentional gaps. Sounds counterintuitive at first, but believe me, it’s a game changer. Strategically leaving something in reserve forces your opponent to prep for contingencies they may not even see coming.
Dr. Angela Liu
That’s such a good point. When you reserve claims in your initial filing, you’re retaining the flexibility to amend after the PTAB decision. Plus, a well-crafted reservation-of-rights clause sets the stage for this. It’s methodical and, honestly, essential if you want to stay ahead of the procedural game.
Erick
And timing’s everything, isn’t it? Monitoring district court scheduling orders ensures you’re filing amendments and disclosures at just the right moment. Miss those deadlines, and your whole strategy falls apart.
Dr. Angela Liu
Absolutely. Take Rule 15 as an example—it’s your friend here for late-stage amendments. As long as your timing aligns with procedural windows, you’re avoiding those “trial by ambush” objections while keeping your fallback claims alive and well.
Erick
And this isn’t just about courtroom finesse. PTAB practice considerations—the way you approach IPRs really matters. You need to think strategically about which claims to challenge—or not challenge—right from the get-go.
Dr. Angela Liu
Exactly. If you’re defending, you want to focus only on Tier 1 claims initially asserted to avoid wasting time and resources. But offensively? You’ve gotta throw the book at the other side—challenge everything plausible, including immaterial variants, to make sure there are no loose ends left for district court.
Erick
And when not challenging immaterially different claims? It's risky. They can come back to haunt you. I’ve seen defendants absolutely blindsided by fallback claims they didn’t take seriously during IPR petitions.
Dr. Angela Liu
It all comes back to leverage, doesn’t it? PTAB invalidation of Tier 1 claims can be used strategically in settlement negotiations, while saving Tier 2 claims as your final trump card. That dual-layered approach is what makes this whole strategy so damn effective.
Erick
Agreed. It’s not just legal chess—it’s chess while simultaneously stacking your deck. Patent holders who integrate this level of planning aren’t just surviving—they’re turning the tables.

Chapter 5

Risk Mitigation Checklist

Erick
Now that we’ve broken down the dual-layered approach and its numerous advantages, let’s shift gears to risk mitigation—another cornerstone of strategic litigation. We’ve got this simple but critical checklist patent holders need to follow to maximize their results. First up, Angela—why is identifying your Tier 1 and Tier 2 claims such a foundational step?
Dr. Angela Liu
Because it’s the foundation of everything else. Separating your broad foundational claims from the narrower fallback ones early on ensures you’re setting up a flexible strategy. You’re building your case to pivot if things go south at any stage.
Erick
Exactly. Next, file that initial complaint focusing just on those Tier 1 claims. That gets the ball rolling without putting all your cards on the table. It’s strategic, controlled, precise.
Dr. Angela Liu
And here’s the nuance—when you file, you’ve gotta plan for the long game. Include a reservation-of-rights clause in your complaint. That way, you leave yourself room to amend and bring in those Tier 2 claims later if needed. Timing’s everything.
Erick
Speaking of timing, that brings us to preparing for IPR challenges. Know the deadlines, anticipate the arguments, and make sure your team is on the same page with PTAB counsel early on. No surprises.
Dr. Angela Liu
Right. And don’t just react—use this phase to evaluate your fallback claims again. Could they withstand a higher standard of proof in district court? If the answer’s yes, you’re in a strong position no matter what happens at the PTAB.
Erick
Which leads us straight to amending your complaint post-PTAB. If your Tier 1 claims don’t make it? No problem. You’ve got those Tier 2s ready to deploy. But play it smart. File those amendments at the right time before you miss scheduling deadlines.
Dr. Angela Liu
Exactly. Courts don’t like surprises, so stick to Rule 15 and the procedural rules in your district. These amendments should feel seamless—not contentious. Make them part of your overarching strategy, not a desperate pivot.
Erick
And finally, keep your patent portfolio updated. Reflect the PTAB outcomes, refine your filing approach, and build smarter strategies for the future. It’s not just about winning the current battle; it’s about setting up for the next one.
Dr. Angela Liu
Couldn’t agree more. Patent litigation isn’t static—it evolves. The more proactive you are about maintaining and managing your portfolio, the stronger your leverage becomes across all fronts.
Erick
And that’s what this checklist ensures. It’s proactive, strategic, and most importantly, it keeps you in control.

Chapter 6

Practical Risk Mitigation Tips for Legal Practitioners

Erick
Angela, as we wrap up the risk mitigation checklist, I’m curious—how do you see coalescing all these steps into an actionable strategy? Especially now, post-Kroy, when the stakes have never been higher?
Dr. Angela Liu
Absolutely, Erick. One of the most critical shifts is timing—monitoring claim schedules and planning amendments with surgical precision. If you don’t, you’re leaving your case vulnerable to unnecessary missteps. It’s not only about doing the right thing, it’s about doing it at precisely the right moment.
Erick
But the devil’s in the details, isn’t it? Think about the tactical challenges—like defending claims that are too broad and risking invalidation, rather than strategically asserting narrower claims in backup rounds.
Dr. Angela Liu
Right, and that’s where structure makes or breaks litigation. Patent portfolio management must account for fallback claims as assets—not afterthoughts. Organize them in tiers, distinguish them carefully, but don’t lose sight of their value in later stages of prosecution or litigation.
Erick
And—I mean, this matters most in adapting for sector-specific nuances. AI-driven patent disputes, for example, require even more foresight. As someone deep in that world, Angela, how do you see Kroy affecting those tech-heavy cases?
Dr. Angela Liu
Well, it’s a game changer for sure. AI patents often involve layered dependencies and iterative frameworks, which makes the staggered strategy all the more relevant. It’s not just a matter of “what claims to assert,” but how to structure them so fallback options retain value if other layers are peeled away through PTAB decisions.
Erick
Layers, I like that. It’s like working with concentric circles—
Dr. Angela Liu
Exactly. And beyond that, owning the narrative is vital. If you’re asserting sequentially, use each phase to reinforce expertise. Adapt defensively but pivot aggressively when the strategy calls for it.
Erick
Couldn’t agree more. A proactive, risk-mitigated strategy not only saves resources but keeps you in control throughout. That’s the crux of thriving post-Kroy.

Chapter 7

Practical Risk Mitigation Tips for Legal Practitioners

Erick
Angela, we’ve covered so much ground around post-Kroy strategies. Before we dive deeper, let’s crystallize what this all means for patent owners. How does this decision redefine strategic priorities?
Dr. Angela Liu
Honestly? It’s the mindset shift this decision demands. You can’t just be reactive anymore. You’ve got to treat your claim portfolio like a chessboard—thinking several moves ahead and layering your strategies to adapt as things unfold, whether you’re at the PTAB or in district court.
Erick
Exactly. And the key word there is layering. A solid strategy starts way before any complaint is filed. It’s about building that foundation—structuring your claims so you’ve always got a fallback. Like, you’re prepping for every contingency, just in case.
Dr. Angela Liu
Right, and that’s why this staggered approach makes so much sense. Assert your strongest claims first to anchor your case, but keep those narrower, immaterially different claims in your back pocket. If the PTAB knocks out the big ones, those fallbacks can still pack a punch in district court.
Erick
It’s kind of poetic, really—turning what looks like a loss into leverage. And timing’s everything here. Be proactive about when and where you assert, so you’re not caught off guard mid-litigation. That precision can make or break a case.
Dr. Angela Liu
That’s so true. And let’s not overlook how this impacts smaller patent owners. I mean, they’re often outgunned resource-wise, but Kroy gives them a way to stay in the fight—by staying flexible and keeping control over their options.
Erick
Couldn’t have said it better myself. And here’s the thing—this isn’t just theory. Post-Kroy, you’ve got a real path forward as long as you plan ahead and take these risk mitigation steps seriously.
Dr. Angela Liu
Exactly. Because at the end of the day, Erick, it’s not about how many claims you can assert or how aggressive your litigation looks on paper. It’s about being smart—about creating pathways to win, even if you stumble along the way.
Erick
And patent owners who adapt to this new reality? They’re not just surviving the system—they’re thriving in it. Angela, talking this through with you has been, well, seriously invaluable.
Dr. Angela Liu
Likewise, Erick. These moments—when the law shifts and we break it down to rebuild better strategies—they’re what make these discussions worthwhile.
Erick
Absolutely agree. And that’s all the time we’ve got for today. Thanks for joining us, everyone. Until next time, keep thinking strategically, and remember, the strongest cases are the ones built step by step.
Dr. Angela Liu
And on that note, we’ll see you next time. Take care!
Erick
Until next time, this is Erick and Angela signing off!

About the podcast

The PTAB Blog by Erick Robinson serves as a vital resource for navigating the Patent Trial and Appeal Board (PTAB). Offering in-depth analyses of decisions, procedural updates, and insights into evolving legal trends, the blog caters to attorneys, inventors, and stakeholders involved in patent disputes. With practical guidance, strategic advice, and focused coverage of landmark rulings and rule changes, it’s an indispensable tool for those handling PTAB matters or post-grant proceedings.