Prosecution Laches

Prosecution laches is an equitable defense to patent infringement that bars enforcement of a patent when the patent owner unreasonably and inexcusably delayed in filing or prosecuting the patent application, and that delay prejudiced the accused infringer. DISTINCTION FROM EQUITABLE LACHES: ordinary equitable laches in patent law (laches in asserting infringement claims) was significantly limited by SCA Hygiene Products v. First Quality Baby Products (S.Ct. 2017), which held that laches cannot bar a claim for damages within the Patent Act's six-year limitations period under § 286; prosecution laches is DIFFERENT — it applies to delay during the prosecution process itself, not delay in suing for infringement. ORIGINS — SUBMARINE PATENTS: prosecution laches developed primarily in response to so-called 'submarine patents' — a pre-GATT (pre-1995) strategy where applicants could file patents, divide them into long chains of continuing applications, and maintain them in secret for decades (patents were not published until grant under the old 17-year-from-grant term); meanwhile, an entire industry would develop around the technology; when the patent eventually issued, the patentee could sue all industry participants; the 1995 GATT implementation changing patent term to 20 years from filing largely eliminated this strategy for new filings. WHY IT STILL MATTERS: prosecution laches applies not only to pre-GATT submarine patents but also to modern continuation chains — if a patent owner files a series of continuation applications that keep claims pending for a decade or more without any adequate explanation, prosecution laches may bar enforcement even under the 20-year term regime.

The Federal Circuit articulated the prosecution laches standard in Symbol Technologies, Inc. v. Lemelson Medical (Fed. Cir. 2004). THE TWO ELEMENTS: (1) UNREASONABLE AND INEXCUSABLE DELAY — the patentee delayed prosecution of the patent for an unreasonable and inexcusable length of time from when the patent owner had the opportunity to seek patent claims; 'unreasonable' is a high bar — not merely deliberate delay, but delay that, in light of the surrounding circumstances, is unjustifiably long; the relevant period is measured from when the patentee could have sought the specific claims at issue to when the claims actually issued; (2) PREJUDICE TO THE ACCUSED INFRINGER — the accused infringer suffered material prejudice attributable to the delay; prejudice can be evidentiary (loss of evidence, witnesses, documents) or economic (investment in a particular technology, industry reliance on the unpatented state of the technology). BALANCING OF EQUITIES: prosecution laches is ultimately an equitable doctrine — even if both elements are met, courts balance the equities; a patentee who actively pursued prosecution (even slowly) is treated differently from one who deliberately kept claims pending to capture a developing industry; the stronger the prejudice to the accused, the lower the bar for unreasonableness. WHAT IS NOT SUFFICIENT: mere long prosecution (e.g., 5 years without extraordinary circumstances) may not alone constitute prosecution laches; the applicant must have had the OPPORTUNITY to seek the claims earlier and unreasonably chose not to.

Continuation applications are the primary modern vehicle for prosecution laches claims, particularly in the post-GATT era: THE CONTINUATION CHAIN STRATEGY: a patent applicant may file a chain of continuation applications — each claiming priority to the original application's filing date — and keep claims pending for years or decades; unlike the pre-GATT submarine patent (which could issue with a 17-year term running from grant), post-GATT continuations are subject to the 20-year term from original filing; but even within that term, a patent issuing 15 years after the original filing can capture 20 years of industry development in just 5 years of patent coverage — still a potentially distorting outcome if the applicant deliberately delayed to capture a developed industry; WHEN LACHES APPLIES TO CONTINUATIONS: courts look at whether the patentee could have sought the same (or substantially similar) claims in earlier-filed applications; if the technology and industry were mature when the claims issued, and the applicant's delay was not driven by legitimate prosecution back-and-forth with the examiner but instead by deliberate claim-holding strategy, laches may apply; KEY FACTORS: (1) how many continuation applications and over what timespan? (2) did the applicant file new claims substantially similar to what was pending all along, or did the claims evolve in response to examiner rejections? (3) was the applicant aware of the allegedly infringing activity during the delay? (4) did the accused infringer invest in the allegedly infringing technology during the delay, relying on the absence of issued claims? DISTINCTION: a long prosecution driven by complex technical issues and genuine back-and-forth with the examiner is far less likely to constitute prosecution laches than one driven by deliberate deferral of allowable subject matter.

Symbol Technologies, Inc. v. Lemelson Medical, Education & Research Foundation (Fed. Cir. 2004) is the leading Federal Circuit case on prosecution laches. THE LEMELSON PATENTS: Jerome Lemelson was a prolific inventor who filed over 500 patents, many through continuation chains that stretched from the 1950s through the 1990s — the classic pre-GATT submarine patent strategy; Lemelson's machine vision and bar code patents, in particular, issued decades after they were filed, by which time entire industries had developed around bar code scanning technology; when Lemelson's estate (and later Lemelson Medical) sued Symbol Technologies and others for infringement, the patents appeared to cover core industrial bar code and machine vision technology. THE HOLDING: the Federal Circuit affirmed the district court's finding of prosecution laches; the court held that prosecution laches was a viable equitable defense that could render patents unenforceable; the relevant inquiry was whether the patentee's delay in pursuing claims was unreasonable and inexcusable AND whether the accused infringer suffered prejudice from the delay; SIGNIFICANCE FOR MODERN CASES: Symbol Technologies confirmed that prosecution laches survives post-GATT and applies not only to extreme pre-GATT submarine patents but potentially to modern continuation strategies as well; any patent issuing from a very long continuation chain is potentially vulnerable to a prosecution laches defense; patent litigants regularly assert prosecution laches against patents with long prosecution histories, particularly those in high-tech or software fields where continuation chains are common.

Patent owners with pending continuation chains should be mindful of prosecution laches risk: (1) DO NOT DELIBERATELY HOLD CLAIMS: the most dangerous conduct is knowingly deferring allowable claims while an industry develops around the technology; actively prosecute claims to allowance as promptly as possible given the examiner's prior art positions; (2) DOCUMENT THE PROSECUTION HISTORY: ensure the prosecution history reflects legitimate back-and-forth with the examiner — rejections, responses, amendments — rather than unexplained long delays; (3) FILE CONTINUATIONS WITH PURPOSE: continuation applications should be filed for legitimate reasons (broader claims to capture additional infringers, continuation of prosecution after abandonment of one line of claims, etc.) — not merely to keep claims pending; (4) MONITOR THE INDUSTRY: be aware of when the industry has developed around the core technology and ensure that prosecution is completed before substantial reliance-based prejudice accumulates; (5) IF PROSECUTION IS NECESSARILY SLOW: document why (technical complexity, interference proceedings, inter partes reexamination, appeals) — legitimate reasons for slow prosecution are a defense to the 'unreasonable' element; (6) CLAIM DIFFERENTIATION WITHIN CONTINUATION CHAINS: don't file continuations with claims nearly identical to what could have been claimed in earlier applications — each continuation should have a clear differentiated purpose.