Induced and contributory infringement
Indirect infringement reaches actors who do not perform the patented invention themselves but who are responsible for inducing or contributing to the direct infringement of another. Liability under § 271(b) and (c) requires actual or willfully blind knowledge of the patent, and § 271(c) is further constrained by a staple-article-of-commerce limitation that excludes products with substantial non-infringing uses.
The rule
The Patent Act provides two independent forms of indirect infringement. Section 271(b) imposes liability on whoever "actively induces infringement of a patent." Section 271(c) imposes liability on whoever sells, offers to sell, or imports a "component of a patented machine, manufacture, combination, or composition, or a material or apparatus for use in practicing a patented process," constituting a material part of the invention, knowing the same to be especially made or especially adapted for use in an infringement and not a staple article or commodity of commerce suitable for substantial non-infringing use.
Both forms of indirect infringement require an underlying act of direct infringement by some party. Both require the defendant to have known of the patent. Section 271(c) additionally requires that the component lack a substantial non-infringing use.
Statutory and constitutional source
Section 271(b) provides simply: "Whoever actively induces infringement of a patent shall be liable as an infringer." Section 271(c) provides:
Whoever offers to sell or sells within the United States or imports into the United States a component of a patented machine, manufacture, combination or composition, or a material or apparatus for use in practicing a patented process, constituting a material part of the invention, knowing the same to be especially made or especially adapted for use in an infringement of such patent, and not a staple article or commodity of commerce suitable for substantial noninfringing use, shall be liable as a contributory infringer.
Both subsections were added to the Patent Act in 1952 to codify and reform the common-law doctrine of contributory infringement that had grown up around Wallace v. Holmes, 29 F. Cas. 74 (C.C.D. Conn. 1871), and that the Supreme Court had partially curtailed in Mercoid Corp. v. Mid-Continent Investment Co., 320 U.S. 661 (1944). Indirect infringement remains a creature of statute, with constitutional foundation in the Patent and Copyright Clause, U.S. Const. art. I, § 8, cl. 8.
The framework the courts apply
Predicate act of direct infringement
Both § 271(b) and § 271(c) require an underlying act of direct infringement. The Supreme Court reaffirmed this requirement in Limelight Networks, Inc. v. Akamai Technologies, Inc., 572 U.S. 915, 921 (2014): "[O]ur case law leaves no doubt that inducement liability may arise if, but only if, [there is] direct infringement." The same applies to contributory infringement under § 271(c). See Aro Manufacturing Co. v. Convertible Top Replacement Co., 365 U.S. 336, 341 (1961) (Aro I).
The direct act may be performed by any party — the customer, the end user, a third-party service provider — and may be proved literally or under the doctrine of equivalents. The patentee must identify a specific direct infringer or, in some cases, a class of direct infringers, and must prove direct infringement by a preponderance of the evidence.
Knowledge of the patent
Both forms of indirect infringement require that the accused inducer or contributor knew of the patent and knew that the induced or contributed acts constituted infringement. The Supreme Court resolved this question definitively in Global-Tech Appliances, Inc. v. SEB S.A., 563 U.S. 754 (2011), holding that induced infringement under § 271(b) requires knowledge that the induced acts infringe, and that "willful blindness" satisfies the knowledge requirement. Id. at 766–70.
Willful blindness, as the Court defined it, requires both (1) a subjective belief that there is a high probability that a fact exists and (2) deliberate actions to avoid learning of that fact. Global-Tech, 563 U.S. at 769. Mere negligence or recklessness is insufficient. Id. at 770.
The Court extended Global-Tech's knowledge framework in Commil USA, LLC v. Cisco Systems, Inc., 575 U.S. 632 (2015), confirming that an induced-infringement claim requires proof that the defendant knew the induced acts constituted patent infringement. The Court also held in Commil that a defendant's good-faith belief that the patent was invalid is not a defense to inducement: invalidity and infringement are separate questions, and a belief that the patent is invalid does not negate the requisite knowledge that the induced acts, if the patent is valid, would infringe. Id. at 642–46.
Specific intent (induced infringement)
Beyond knowledge, induced infringement requires specific intent — affirmative intent to cause the direct infringement. The Federal Circuit articulated this requirement in DSU Medical Corp. v. JMS Co., 471 F.3d 1293 (Fed. Cir. 2006) (en banc in relevant part), holding that inducement requires "more than just intent to cause the acts that produce direct infringement"; it requires "knowledge that the induced acts constitute patent infringement." Id. at 1304–06. The DSU Medical standard was expressly endorsed by Global-Tech.
Specific intent may be proved by circumstantial evidence. Common evidence includes instructions, advertising, technical support, training materials, and product documentation that direct customers to perform infringing acts. See Vita-Mix Corp. v. Basic Holding, Inc., 581 F.3d 1317, 1328–29 (Fed. Cir. 2009) (instructions and advertising).
Material part and "especially made" (contributory infringement)
Section 271(c) requires that the component constitute a "material part of the invention" and be "especially made or especially adapted for use in an infringement." A component is "especially made" for infringement when its intended and actual use is to be incorporated into the patented combination. See Aro Manufacturing Co. v. Convertible Top Replacement Co., 377 U.S. 476, 488 (1964) (Aro II) (knowledge of the patent and of the infringing use is required).
The "material part" requirement has been read to mean that the component is an important part of the patented invention, although courts rarely apply it independently. The principal contestable elements of contributory infringement are the knowledge requirement and the staple-article exclusion.
Staple article of commerce; substantial non-infringing use
Section 271(c) does not reach "a staple article or commodity of commerce suitable for substantial noninfringing use." This limitation is the central textual constraint on contributory infringement. A component that has substantial non-infringing uses cannot give rise to contributory liability, however clearly the seller knew or intended that the component would be used in an infringing combination. The Supreme Court emphasized this point in Aro II, 377 U.S. at 487–88.
The Federal Circuit has held that the relevant inquiry is whether the accused component, as actually distributed and used, has substantial non-infringing uses, not whether some hypothetical alternative could be used. See i4i Limited Partnership v. Microsoft Corp., 598 F.3d 831, 851 (Fed. Cir. 2010), aff'd on other grounds, 564 U.S. 91 (2011). "Substantial" is not the same as "any": occasional or theoretical non-infringing uses do not save the seller. Vita-Mix, 581 F.3d at 1327.
Burden and proof
The patentee bears the burden of proving each element of indirect infringement by a preponderance of the evidence. Indirect infringement, like direct infringement, is a question of fact. Knowledge of the patent and specific intent are typically proved by circumstantial evidence: notice letters, prior litigation, technical documentation, internal communications, and customer-facing materials.
Pleading. Under Bell Atlantic Corp. v. Twombly, 550 U.S. 544 (2007), and Ashcroft v. Iqbal, 556 U.S. 662 (2009), induced and contributory infringement claims must include factual allegations sufficient to give rise to a plausible inference of pre-suit knowledge of the patent. After the abrogation of Form 18 of the Federal Rules of Civil Procedure in 2015, district courts have routinely required specific allegations identifying the source and timing of pre-suit knowledge. Filing of the complaint itself can supply post-suit knowledge.
Interaction with related doctrines
Indirect infringement requires direct infringement as a predicate. The two doctrines are intertwined: many cases pursue direct infringement against the supplier and induced or contributory infringement on a fallback theory, particularly for method claims where customer participation is required. Where divided infringement is at issue, indirect infringement may not be available unless the underlying direct infringement satisfies Akamai.
Knowledge and intent under § 271(b) overlap with — but are distinct from — the subjective culpability inquiry for willfulness under Halo Electronics, Inc. v. Pulse Electronics, Inc., 579 U.S. 93 (2016). A finding of inducement does not automatically establish willfulness, but the same evidence often supports both theories.
The good-faith-belief-of-invalidity rule of Commil bears on counsel's role. Defendants commonly rely on opinions of counsel and PTAB challenges to negate the knowledge element, but Commil clarifies that an invalidity opinion does not, on its own, negate the knowledge of infringement required by § 271(b). See inter partes review; IPR estoppel.
Indirect infringement claims are also affected by exhaustion: an authorized sale exhausts the patent rights as to that article and bars subsequent inducement or contributory claims arising from the buyer's downstream conduct.
Practical notes
- Pre-suit notice letters are pivotal. They establish knowledge of the patent and start the clock on potential damages, but they also put the alleged infringer on notice and may trigger declaratory-judgment risk.
- For software and component suppliers, the staple-article defense is often the principal theory of non-liability under § 271(c). Demonstrating substantial non-infringing uses with concrete customer evidence is the goal.
- Inducement claims against service providers typically point to user manuals, installation guides, and training materials. Defendants who include warnings or instructions discouraging the infringing use can argue against specific intent, though such warnings are not dispositive.
- Post-suit conduct can supply both knowledge and intent. Continued sales and instruction after notice — particularly after a preliminary injunction or denial of summary judgment of non-infringement — can be powerful evidence.
- Indirect-infringement claims depend on the strength of the direct-infringement theory. A flawed direct-infringement theory is fatal to inducement and contributory claims regardless of how compelling the intent evidence is.
- Where the same conduct could support both inducement and contributory infringement, plaintiffs typically plead both. § 271(c) is narrower (and provides less flexible damages exposure) but is sometimes easier to prove because it does not require the affirmative-intent showing of DSU Medical.
Open questions
The exact contours of "willful blindness" remain contested at the margins. Global-Tech drew a sharp line between willful blindness and recklessness, but lower courts have applied the test inconsistently when the defendant has unread notice letters or has merely received a citation in a portfolio of patents. The Federal Circuit has addressed willful blindness several times since Global-Tech but has not yet generated a comprehensive doctrinal framework.
The treatment of post-suit knowledge for damages purposes is also unsettled. Courts agree that filing a complaint can supply post-suit knowledge sufficient for inducement, but they differ on whether pre-suit damages can be recovered absent pre-suit knowledge — and on the role of the marking statute, 35 U.S.C. § 287, in indirect-infringement cases.
See also
- Direct infringementPredicate act required for indirect liability.
- Literal infringementStandard infringement test.
- WillfulnessSubjective culpability inquiry under Halo.
- Inter partes reviewCommon venue for invalidity challenges.
- Patent exhaustionFirst-sale defense.
- Claim constructionFoundation for both direct and indirect infringement.
Last reviewed: 2026