If you have received a cease-and-desist letter asserting a design patent, or if you are already a defendant in a design patent infringement lawsuit, your first instinct may be to wonder whether the patent is even valid.  It is a fair question.  Design patents i

ssue relatively quickly – the Rocket Docket program can get a design patent to grant in under a year – and they generally receive more limited examination compared to utility patents.  They are sometimes granted on designs that, on reflection, look a lot like things that existed long before the patent was filed.  So can you invalidate one?

Yes, you can.  Several paths exist, and the right one depends on where you are in the dispute, how much you want to invest, and how strong your invalidity arguments are.

What Makes a Design Patent Invalid?

Before choosing a route to invalidation, it helps to understand the grounds.  As noted in prior posts, the drawings in a design patent define the scope of protection — both what the patent covers and what it does not.  That drawing-centric nature shapes the invalidity analysis.  A design patent is invalid if:

• The design is not new or anticipated.  If the same or a substantially similar ornamental design appeared in a prior publication, product, patent, or public use before the filing date of the challenged patent, the patent should never have issued.  A good patent search uncovers this kind of prior art.  This is can be the most powerful invalidity ground.
• The design is obvious.  Even if no single prior art reference discloses the exact design, a combination of references can render the design obvious to a designer of ordinary skill.  The standard for this analysis has recently shifted significantly, and has made obviousness easier to establish.
• The design is functional, not ornamental.  Design patents protect the ornamental appearance of an article, not its function.  If the elements of the claimed design are dictated by function rather than aesthetic choice, the design falls outside the scope of design patent protection.
• The drawing disclosure is inadequate.  As the Patent Office’s own manual puts it, an insufficient drawing may be fatal to validity.  Poor drawing quality, something I have written about before, can become a validity issue after the patent grants, just as it is during prosecution.

Route 1: Invalidity as a Defense and Counterclaim in Litigation

The most common setting in which invalidity comes up is a lawsuit.  When a patent owner sues for infringement, the defendant can and typically does assert invalidity as an affirmative defense.  The defendant can also assert a counterclaim for a declaration that the patent is invalid.

The burden in litigation is a demanding one.  Patents are presumed valid under 35 U.S.C. § 282, and a defendant must prove invalidity by clear and convincing evidence.  This is a higher standard than the preponderance of the evidence standard that applies in most civil litigation.

Still, the presumption of validity is not insurmountable, particularly for design patents.  Design patent examiners work quickly.  Prior art searches for design patents are narrower in scope than those for utility patents.  There can be a not unreasonable chance that strong prior art exists that the examiner never considered.

One additional defense worth knowing about in design patent litigation is prosecution history estoppel.  This allows a defendant to argue that the patent owner surrendered some scope of protection during prosecution and cannot now assert that surrendered scope against the defendant’s product.  For example, canceling one of multiple design embodiments can estop the patent owner from claiming that the one embodiment is covered.  Courts have confirmed that prosecution history estoppel applies in design patent cases just as it does in utility patent cases.

Practical takeaway: litigation is expensive, and invalidity in court is difficult to establish.  But a credible invalidity defense can be a powerful settlement lever, and asserting it is a baseline move for any defendant.

Route 2: Declaratory Judgment Action

If you have not yet been sued but a patent owner has put you on notice, such as with a cease-and-desist letter, licensing demand, or pattern of threatening conduct, you may be able to bring a proactive lawsuit seeking a declaration that the patent is invalid and/or not infringed.

This is called a declaratory judgment action.  To file one, you need to establish that there is a “case or controversy,” meaning that the threat of suit must be real and immediate, not speculative.  A well-worded cease-and-desist letter generally satisfies this requirement.

Declaratory judgment actions give you control over timing and venue.  Rather than waiting to be forced into a court of the patent owner’s choosing, you can file in a jurisdiction that is convenient for you and move the dispute forward on your own schedule.

The same standards apply as in a defensive invalidity claim — clear and convincing evidence, and the presumption of validity.  And, since a DJ action is a federal court action, there are significant costs involved in such a suit.

Route 3: Inter Partes Review (IPR) — Available, But Difficult

Inter Partes Review is a trial proceeding at the Patent Trial and Appeal Board (PTAB) of the USPTO in which a petitioner challenges the validity of an issued patent based on prior art.  An IPR is technically available for design patents.  However, there are difficulties involved in an IPR.

According to Sterne Kessler’s January 2026 review of design patents at the PTAB, inter partes activity involving design patents was low in 2025, as it was in 2024.  The PTAB rendered only two inter partes decisions involving design patents in all of 2025, and both declined to institute review.  The design patent institution rate has now slipped to 37%, compared to roughly 64% for utility patents.  Even where institution is granted, the design patent claim invalidation rate at the final written decision stage is 65%, compared to about 75% for utility patents.

Why Is the Institution Rate So Low?

The difficulty lies in proving obviousness.  For decades, design patent obviousness was assessed under the Rosen-Durling test, which required that a primary reference be “basically the same” as the claimed design before secondary references could even be considered.  In May 2024, the Federal Circuit scrapped that test in LKQ Corp. v. GM Global Tech. Operations LLC and replaced it with the more flexible factors long used for evaluating obviousness in utility patents.

That would seem to suggest good news for challengers.  But PTAB’s 2025 decisions suggest the Board is applying the new framework rigorously.  In both 2025 cases, the PTAB found that petitioners failed to adequately explain why a designer of ordinary skill would have modified the cited primary reference with elements from secondary references.  As a result, the Board denied institution in both cases.

Other IPR Considerations

IPRs have several features that distinguish it favorably from litigation: the burden of proof is preponderance of the evidence rather than clear and convincing; there is no presumption of validity; and PTAB judges have technical and legal training.  However, there are downsides:

• Estoppel risk.  If you file an IPR and the Board institutes the proceeding, you may be estopped from raising in later litigation any ground you raised or reasonably could have raised in the IPR.
• Timing constraint.  A petition must be filed within one year of being served with a complaint for infringement.  If you have been sued, that clock is ticking.
• New procedural hurdles.  In March 2025, the USPTO’s director issued a memorandum implementing interim procedural changes to the IPR and PGR institution phase.  These changes create additional procedural steps that petitioners must navigate.

The bottom line on IPR for design patents is that it remains a legitimate option, particularly when you have strong prior art patents or printed publications, but it has a lower-than-average institution rate and heightened scrutiny when it comes to obviousness arguments.

Route 4: Post-Grant Review (PGR)

Post-Grant Review is another AIA proceeding at PTAB.  Unlike IPRs, PGRs allow a broader range of invalidity arguments in addition to prior-art-based grounds, such as functionality challenges and inadequate disclosure arguments.

The catch is timing.  A PGR petition must be filed within nine months of the grant or reissuance of the patent.  After that window closes, PGR becomes unavailable.

If you learn about a problematic design patent within that nine-month window, PGR is worth serious consideration, especially if you have a functionality argument that would not be available in an IPR.

Route 5: Ex Parte Reexamination

Ex parte reexamination is an older USPTO proceeding that allows any person to ask the Patent Office to reexamine an issued patent based on prior art patents or printed publications.  Unlike IPR, it is one-sided: after the request is filed and accepted, the requestor largely steps back, and the examination is conducted between the patent owner and the examiner.

Reexamination is available for design patents.  It is generally less expensive than IPR, and because it is ex parte (without an adversary or opponent), it does not carry the same estoppel consequences.  The trade-off is that the patent owner has significant opportunity to amend claims and argue with the examiner, which can result in a narrowed rather than canceled patent.

Choosing the Right Path

No single route is right for every situation.  A few practical considerations:

• Are you already in litigation?  Asserting invalidity as a defense and counterclaim is a baseline move.  Depending on the strength of your prior art, filing an IPR petition may also make sense, but you must watch the one-year deadline and the estoppel consequences carefully.
• Have you been threatened but not yet sued?  A declaratory judgment action puts you in the driver’s seat on venue and timing.  If your prior art consists entirely of patents and printed publications, an IPR may also be worth considering, but review the institution statistics before committing.
• Is the patent recently issued?  If it has been fewer than nine months since the patent granted, Post-Grant Review opens up a broader set of arguments, including functionality.
• How strong is your prior art?  The stronger your prior art, the more attractive PTAB proceedings become, given the lower burden of proof.  If your prior art is thin, a challenge in any forum may be difficult.

A Word About the Stakes in Design Patent Litigation

Design patent litigation has become increasingly active in the US, and a well-developed invalidity strategy is important when you are on the receiving end of a design patent claim.  If you are facing a design patent dispute, understanding all of your options and the realistic prospects for each is an important early step.  It is imperative to contact competent patent counsel for advice.

I’m Tom Galvani, a patent and trademark lawyer in Phoenix, Arizona.  I help inventors, entrepreneurs, and businesses develop and protect their intellectual property.  If you have questions about design patent validity or any other patent matter, feel free to contact me.