What is laches?
Laches is a Latin term meaning 'negligence' or 'unreasonable delay.' As an equitable defense in patent law, it prevented a patent holder from recovering damages when they unreasonably delayed filing suit after learning of the infringement, and that delay caused the defendant material prejudice. Courts required two elements: (1) the patent holder's unreasonable and unjustified delay in filing suit; and (2) material prejudice to the defendant — either economic prejudice (the defendant substantially invested in the infringing activity during the delay period, making it more expensive to stop) or evidentiary prejudice (key witnesses died or moved away, documents were destroyed, memories faded). Historically, courts presumed laches when the delay exceeded 6 years from when the patent holder knew or should have known of the infringement.
SCA Hygiene (2017): the Supreme Court limits laches
The Supreme Court significantly curtailed the laches defense in SCA Hygiene Products Aktiebolag v. First Quality Baby Products (2017). The Court held that laches cannot bar a patent infringement damages claim for conduct within the 6-year statutory period under 35 U.S.C. § 286. The Court reasoned that Congress already calibrated the appropriate time limit for damages in § 286, and allowing courts to further shorten that period through laches would override the legislative judgment. The decision overruled the Federal Circuit's 1992 en banc Aukerman decision and harmonized patent law with copyright law (Petrella v. MGM, 2014). After SCA Hygiene, a patent holder can always recover damages for infringement within the 6 years before suit, regardless of how long they waited to sue.
Laches after SCA Hygiene: remaining relevance
Although SCA Hygiene eliminated laches as a bar to damages within the 6-year lookback period, laches retains some relevance. For equitable relief (injunctions), courts still consider a patent holder's delay in the broader equitable analysis under eBay v. MercExchange (2006). If a patent holder watched a defendant invest heavily in infringing technology for years before suing, that delay may weigh against granting a permanent injunction even if the patent is valid and infringed. For conduct outside the 6-year limitation period (i.e., damages accruing more than 6 years before the lawsuit), § 286 itself bars recovery — so laches adds little. For prosecution laches (a separate doctrine in prosecution), laches can still render an issued patent unenforceable.
Prosecution laches: a different doctrine
Prosecution laches is an entirely separate doctrine that applies during USPTO prosecution. It can render a patent unenforceable when an applicant unreasonably and unjustifiably delayed the prosecution of a patent application in a manner that prejudices accused infringers. The classic prosecution laches scenario: an applicant files a patent in, say, 1975, keeps a continuation application pending by filing continuation after continuation, waits 25+ years for the relevant industry to develop, and then allows claims to issue in 2000 — claiming priority back to 1975 — and then asserts those claims against companies that built entire industries during the 25-year pendency. Symbol Technologies v. Lemelson Medical (Fed. Cir. 2004) confirmed prosecution laches as a valid enforceability defense. The doctrine is narrowly applied and requires showing both unreasonable delay and prejudice.
Equitable estoppel: related but distinct
Laches is often confused with equitable estoppel, which is a related but distinct equitable defense. Equitable estoppel requires: (1) the patent holder communicated (through action, inaction, or misleading conduct) that it would not enforce its patent against the defendant; (2) the defendant relied on that conduct; and (3) due to that reliance, the defendant would be materially prejudiced if the patent holder is now permitted to enforce. Unlike laches (which is about unreasonable delay alone), equitable estoppel requires an affirmative misleading communication or conduct by the patent holder. After SCA Hygiene, equitable estoppel remains a viable defense that can still bar damages claims — it requires the additional element of misleading conduct that laches alone does not require.
Statute of limitations: § 286
35 U.S.C. § 286 provides: 'No recovery shall be had for any infringement committed more than six years prior to the filing of the complaint or counterclaim for infringement in the action.' This is the statutory damages cutoff that applies regardless of equitable considerations. It runs from when the infringement occurred — not from when the patent holder learned of the infringement. The 6-year lookback period resets each day new infringing acts occur, so ongoing infringement means the patent holder can always recover for the 6 years immediately preceding the lawsuit (subject to SCA Hygiene). Patent holders should note that § 286 runs from the date of each infringing act, not from when the patent issued or when knowledge of infringement arose — meaning patent holders can sue for infringement that occurred before they were aware of it, as long as it falls within the 6-year window.
Frequently Asked Questions
What is laches in patent law?
Laches is an equitable defense to patent infringement that may bar a patent holder's claims for damages when: (1) the patent holder unreasonably and inexcusably delayed filing suit after knowing of the alleged infringement; and (2) the defendant was materially prejudiced by that delay (either by economic prejudice — investing in the infringing product line during the period of delay — or evidentiary prejudice — key witnesses unavailable or evidence lost). Historically, courts applied a presumption of laches when the patent holder delayed filing suit for more than 6 years after knowing of the infringement. However, SCA Hygiene Products Aktiebolag v. First Quality Baby Products (U.S. Supreme Court 2017) significantly limited the laches defense by holding that laches cannot bar a claim for damages within the patent statute's 6-year limitations period under 35 U.S.C. § 286.
What did SCA Hygiene v. First Quality Baby Products hold about laches?
In SCA Hygiene Products v. First Quality Baby Products (U.S. Supreme Court 2017), the Supreme Court held that the equitable defense of laches cannot bar a claim for damages for patent infringement that occurred within the 6-year statutory period under 35 U.S.C. § 286. The decision resolved a circuit split and overruled the Federal Circuit's en banc decision in Aukerman Co. v. R.L. Chaides Construction (1992), which had allowed laches to bar damages within the limitations period. After SCA Hygiene, laches can no longer prevent a patent holder from recovering damages that accrued within 6 years before the lawsuit was filed. However, laches may still be relevant to equitable relief (injunctions) and in some circumstances as a defense to willfulness. The case followed the Court's similar ruling in Petrella v. Metro-Goldwyn-Mayer (2014), which limited laches in copyright law.
What is prosecution laches?
Prosecution laches is a separate doctrine from litigation laches — it operates during patent prosecution to prevent a patent from issuing (or to render it unenforceable after issuance) when the applicant has unreasonably and unjustifiably delayed the issuance of a patent in a way that prejudices the public or accused infringers. Unlike litigation laches (which is a defense in court), prosecution laches is a patent validity/enforceability doctrine. It typically arises when an applicant has kept continuation applications pending for an extremely long period (sometimes decades) by filing a series of continuation applications, then asserts the eventually-issued patent against products/practices that became established during the long pendency period. In Symbol Technologies v. Lemelson Medical (Fed. Cir. 2004), the Federal Circuit confirmed that prosecution laches is a valid basis for rendering a patent unenforceable if there was an unreasonable and unexplained delay in prosecution that prejudiced accused infringers.
How is laches different from the statute of limitations?
The patent statute of limitations under 35 U.S.C. § 286 bars recovery of damages for infringement that occurred more than 6 years before the suit was filed. This is a statutory time limit, not an equitable defense — it applies automatically regardless of prejudice or unreasonable delay. Laches, by contrast, is an equitable defense that required showing both unreasonable delay AND material prejudice to the defendant. The key difference after SCA Hygiene (2017): laches can no longer shorten the 6-year lookback period for damages. The statute of limitations is a hard cutoff; laches is now primarily relevant only for conduct outside the limitations period or for equitable relief (injunctions). Before SCA Hygiene, laches could theoretically bar damages for conduct within the 6-year period if the delay was particularly egregious — that is no longer the case.
Can laches still affect injunctions after SCA Hygiene?
Yes. SCA Hygiene limited laches as a defense to damages claims. For equitable relief — including permanent injunctions and preliminary injunctions — laches (or its more general equivalent, 'equitable considerations') may still be relevant. Under eBay v. MercExchange (S.Ct. 2006), courts apply a four-factor test for permanent injunctions in patent cases: (1) irreparable injury; (2) inadequate remedy at law; (3) balance of hardships; (4) public interest. A patent holder's unreasonable delay in filing suit — even if it doesn't bar damages under SCA Hygiene — may weigh against granting injunctive relief if the defendant has substantially invested in the infringing product during the period of delay, because denying the injunction is less harsh when the patent holder could have acted sooner to prevent the investment.