Patents

The Submarine Surfaces: Symbol Technologies v. Lemelson and the Revival of Prosecution Laches

The Federal Circuit affirmed that decades of unreasonable, unexplained delay in prosecuting continuation applications can render the resulting patents unenforceable.

September 3, 2025
Barcode scanner reading a product label on a warehouse conveyor
Lemelson's bar-code and machine-vision claims issued decades after their 1950s parent applications, triggering the modern prosecution-laches defense. Shutterstock
Educational content, not legal advice. This article explains general legal concepts. It does not create an attorney–client relationship. For your specific situation, consult a licensed attorney.

In Symbol Technologies, Inc. v. Lemelson Medical, Education & Research Foundation, LP, No. 04-1451 (Fed. Cir. Sept. 9, 2005), the U.S. Court of Appeals for the Federal Circuit confirmed that a once-dormant equitable doctrine—prosecution laches—has real teeth. The court affirmed a judgment from the U.S. District Court for the District of Nevada (Judge Philip M. Pro) holding fourteen of Jerome Lemelson’s bar-code and machine-vision patents unenforceable because the inventor had delayed eighteen to thirty-nine years in filing and prosecuting the asserted claims. The decision is the modern cornerstone of prosecution laches: it establishes that unreasonable and unexplained delay during prosecution—even delay achieved through technically lawful continuation practice—can forfeit a patent.

At a glance

  • Parties: Symbol Technologies and Cognex Corporation (declaratory-judgment plaintiffs and manufacturers of bar-code and machine-vision equipment) versus the Lemelson Foundation, which had licensed Lemelson’s patents to hundreds of companies.
  • The patents: Fourteen patents-in-suit covering machine-vision and automatic-identification (bar-code) technology, claiming priority to applications Lemelson first filed in 1954 and 1956.
  • The delay: The asserted claims issued only after delays of 18 to 39 years, achieved through a long chain of continuation and divisional applications that kept the inventions pending while the underlying technology became commercially ubiquitous.
  • District court: After a 27-day bench trial, Judge Pro held the asserted claims unenforceable under prosecution laches (and also found non-infringement and invalidity).
  • Holding (Fed. Cir.): Affirmed. Prosecution laches is a valid defense that renders a patent unenforceable when it issues after an unreasonable and unexplained delay in prosecution, judged on the totality of the circumstances.

The “submarine patent” problem

Lemelson’s patents are the textbook example of the submarine patent. Under the law in force when he filed, patent term ran seventeen years from the issue date, and applications were kept secret until they issued. An applicant could file a broad disclosure, then keep it submerged for decades through serial continuations—amending claims along the way to read on technologies that competitors independently developed and commercialized in the interim. When the patent finally surfaced and issued, its seventeen-year clock started fresh, and the patentee could demand royalties from an entire mature industry that had built itself in reliance on the apparent absence of any patent.

That is precisely the dynamic the district court found. Lemelson’s 1950s applications were the nominal source of the claims, but the specific claims asserted against Symbol and Cognex were prosecuted and allowed many years—sometimes decades—later, after machine vision and bar coding had become foundational to retail, manufacturing, and logistics. The doctrine of prosecution laches exists to police exactly this kind of strategic delay.

Reviving a dormant doctrine

Prosecution laches was not invented in Symbol Technologies; it traces to early twentieth-century Supreme Court decisions (notably Woodbridge v. United States and Webster Electric Co. v. Splitdorf Electrical Co.) recognizing that a patentee who unreasonably delays issuance can forfeit rights. But the doctrine had lain largely unused for generations, and many assumed it had been superseded by the detailed timing rules of the Patent Act. In an earlier appeal in this same litigation, the Federal Circuit held that prosecution laches remained available as a defense in actions involving patents prosecuted under the pre-URAA regime. The 2005 decision is where that revived doctrine was actually applied to invalidate—functionally—an entire patent family.

Crucially, the court rejected the argument that compliance with the PTO’s procedural rules immunizes an applicant. Filing continuations is lawful; the Patent Act and PTO rules permit them. But the court held that legitimate use of the continuation system does not foreclose a laches defense when the pattern and duration of the prosecution become unreasonable. In other words, an applicant can follow every rule and still lose the patent if the cumulative delay is egregious and unexplained.

No bright line—an equitable, totality inquiry

The opinion is notable for what it declines to do: it sets no firm time limit. The court expressly refused to adopt a rule that any fixed number of years of delay automatically constitutes laches, or that any period is automatically safe. Instead, prosecution laches is an equitable doctrine assessed on the totality of the circumstances. Relevant considerations include the length of the delay, the reasons offered (or not offered) for it, the number and nature of the continuation filings, and—importantly—the prejudice to others, such as intervening private and public rights that accrued while the application stayed pending.

This equitable, fact-bound character is both the doctrine’s strength and its limitation. It lets courts reach the worst abuses without disturbing routine, good-faith continuation practice, but it gives prosecutors and litigants little ex ante certainty about where the line falls. The court accepted that trade-off deliberately, trusting district courts to weigh the equities case by case—as Judge Pro had done over a 27-day trial and hundreds of pages of post-trial briefing.

Open questions

Symbol Technologies left the contours of the doctrine intentionally soft. The first open question is how the analysis applies to post-URAA patents. Because term now runs twenty years from the earliest filing date, the classic submarine incentive is largely gone—delay no longer extends the monopoly the way it once did. Whether prosecution laches retains the same force, or any force, against modern continuation chains is a live issue that later cases have begun to probe. Second, the prejudice element remains under-theorized: the court spoke of intervening rights, but how much reliance by competitors or the public a defendant must show, and whether prejudice is strictly required, continues to vary. Third, the relationship between prosecution laches and other tools—double patenting, written description, and the PTO’s own continuation limits—remains unsettled, leaving overlapping doctrines that courts must coordinate.

Implications

  • Lawful continuation practice is not a safe harbor. Following every PTO rule will not save a patent if the overall pattern of delay is unreasonable and unexplained.
  • Delay must be justified on the record. Applicants who keep families pending for many years should be able to articulate legitimate, good-faith reasons; “unexplained” delay is what the doctrine punishes.
  • Prejudice to the public matters. Intervening rights—an industry built in reliance on the apparent absence of a patent—strengthen a laches defense.
  • The defense is equitable and fact-intensive. There is no magic number of years; expect totality-of-the-circumstances litigation, often requiring a full trial record.
  • The submarine incentive has waned, but the doctrine survives. Post-URAA term rules blunt the classic abuse, yet Symbol Technologies remains the controlling framework whenever delay is at issue.

Frequently asked questions

What is prosecution laches? Prosecution laches is an equitable doctrine under which a patent may be held unenforceable if it issued after an unreasonable and unexplained delay in prosecution that prejudiced others. Symbol Technologies confirmed the doctrine is alive and applied it to patents whose claims issued decades after their 1950s parent applications.

If continuation applications are legal, how can using them cost you the patent? Filing continuations is permitted, but Symbol Technologies held that lawful use of the continuation system does not immunize an applicant from laches. When the cumulative duration and pattern of delay become unreasonable and unexplained—and others are prejudiced—the resulting claims can be forfeited even though no individual filing broke any rule.

Is there a fixed number of years that triggers prosecution laches? No. The Federal Circuit expressly declined to set a bright-line period. Prosecution laches is judged on the totality of the circumstances, weighing the length and reasons for the delay, the prosecution conduct, and the prejudice to intervening public and private interests.

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