Patent Infringement Under 35 U.S.C. § 271: Direct, Induced and Contributory

Sources: 35 U.S.C. § 271; Global-Tech Appliances, Inc. v. SEB S.A., 563 U.S. 754 (2011); Commil USA, LLC v. Cisco Systems, Inc., 575 U.S. 632 (2015). Each row is explained below.

Section 271(a) lists five acts (making, using, offering to sell, selling and importing), each without authority and during the patent term. An offer to sell counts only if the sale would occur before the patent expires (§ 271(i)), and "whoever" includes States (§ 271(h)).

Infringement is measured against the claims, one element at a time. The Supreme Court framed "the essential inquiry" in Warner-Jenkinson v. Hilton Davis (1997) this way: "Does the accused product or process contain elements identical or equivalent to each claimed element of the patented invention?" An accused product with an element identical to each claimed element infringes literally. One that matches some elements only by an equivalent may infringe under the doctrine of equivalents, which the Court reaffirmed in that case, with these limits:

• Element by element. "Each element contained in a patent claim is deemed material to defining the scope of the patented invention, and thus the doctrine of equivalents must be applied to individual elements of the claim, not to the invention as a whole." It may not be applied so broadly that it effectively eliminates an element.
• Function, way and result, or insubstantial differences. The Court declined to pick one test. It said the analysis of each element’s role "will thus inform the inquiry as to whether a substitute element matches the function, way, and result of the claimed element, or whether the substitute element plays a role substantially different from the claimed element."
• Timing. Equivalence is judged "at the time of infringement, not at the time the patent was issued."
• Prosecution history estoppel remains a defense. If an amendment required during prosecution had a purpose unrelated to patentability, the court must consider that purpose in deciding whether an estoppel applies.

Sources: 35 U.S.C. § 271(a), (h), (i); Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997).

A method claim is often performed partly by one company and partly by its customers. The en banc Federal Circuit set the rule in Akamai Technologies v. Limelight Networks (2015): "Direct infringement under § 271(a) occurs where all steps of a claimed method are performed by or attributable to a single entity." Another party’s steps are attributed to an accused infringer in two situations:

1. Direction or control. This includes acting through an agent, contracting with another to perform steps, and, the court added, where the accused infringer "conditions participation in an activity or receipt of a benefit upon performance of a step or steps of a patented method and establishes the manner or timing of that performance."
2. Joint enterprise. This requires an agreement among the group, a common purpose, a community of pecuniary interest in that purpose, and an equal right to a voice in the direction of the enterprise.

Both are questions of fact. The rule matters for inducement too: the Supreme Court held in Limelight v. Akamai (2014) that "liability for inducement must be predicated on direct infringement," so if no single entity performs or is responsible for every step, there is no one whose infringement could have been induced.

Sources: Akamai Technologies, Inc. v. Limelight Networks, Inc., No. 2009-1372 (Fed. Cir. Aug. 13, 2015) (en banc); Limelight Networks, Inc. v. Akamai Technologies, Inc., 572 U.S. 915 (2014).

Section 271(b) has one sentence: "Whoever actively induces infringement of a patent shall be liable as an infringer." The Supreme Court summarized the elements in Hikma Pharmaceuticals v. Amarin Pharma (June 4, 2026), drawing on three earlier decisions:

1. Direct infringement by a third party (Limelight, 2014).
2. Knowledge that "the induced acts constitute patent infringement" (Global-Tech, 2011). Commil v. Cisco (2015) reaffirmed that the defendant must know of the patent and know the induced acts infringe. Willful blindness satisfies this element only if the defendant subjectively believed there was a high probability that a fact existed and took deliberate actions to avoid learning it; deliberate indifference to a known risk that a patent exists is not enough.
3. Active steps to encourage direct infringement. Inducement "must involve the taking of affirmative," as opposed to passive, steps, and "ordinary acts incident to product distribution" do not suffice.

Belief in invalidity is no defense. Commil held that a defendant’s good-faith belief that the patent is invalid does not negate the knowledge § 271(b) requires, because "infringement and validity are separate issues under the Act." Knowledge of infringement is a different matter: Commil reaffirmed that Global-Tech "requires proof the defendant knew the acts were infringing," not merely that they might infringe.

Skinny labels. Hikma involved a generic drug label that carved out a patented use. The Court held, unanimously, that the brand owner had failed to state a claim for active inducement: the question is whether the complaint plausibly alleges that the generic maker actively encouraged infringing use, not merely whether doctors could plausibly read its statements as instructions to infringe. Statements with an "obvious alternative explanation," such as compliance with the law (a generic label must by statute match the brand label except for the carved-out use) or standard industry practice (calling the drug a generic equivalent), did not count, nor did "mere omissions, inactions, or nonfeasance."

Sources: 35 U.S.C. § 271(b); Hikma Pharmaceuticals USA Inc. v. Amarin Pharma, Inc., No. 24-889 (U.S. June 4, 2026); Global-Tech Appliances, Inc. v. SEB S.A., 563 U.S. 754 (2011); Commil USA, LLC v. Cisco Systems, Inc., 575 U.S. 632 (2015); Limelight Networks, Inc. v. Akamai Technologies, Inc., 572 U.S. 915 (2014).

Contributory infringement targets suppliers of parts. A person is liable if it sells or offers to sell in the United States, or imports, a component of a patented invention, or a material or apparatus for use in a patented process, that is a material part of the invention, that it knows is especially made or adapted for use in infringing the patent, and that is not a staple article or commodity suitable for substantial noninfringing use.

The knowledge standard matches inducement: "Like induced infringement, contributory infringement requires knowledge of the patent in suit and knowledge of patent infringement" (Commil, citing Aro Mfg. Co. v. Convertible Top Replacement Co. (1964)). Section 271(d) adds that enforcing the patent or refusing to license it is not patent misuse.

Sources: 35 U.S.C. § 271(c), (d); Commil USA, LLC v. Cisco Systems, Inc., 575 U.S. 632 (2015).

Section 271(e) is the patent side of the Hatch-Waxman framework for generic drugs, extended to biosimilars.

• The research safe harbor, § 271(e)(1). It is not infringement to make, use, offer to sell, sell or import a patented invention "solely for uses reasonably related to the development and submission of information" under a federal law regulating drugs or veterinary biological products.
• The filing is the infringement, § 271(e)(2). Submitting an abbreviated new drug application under § 505(j) of the Federal Food, Drug, and Cosmetic Act, a § 505(b)(2) application, certain veterinary applications, or a covered biosimilar application is an act of infringement if its purpose is approval to commercially make, use or sell a patented drug or biologic, or one whose use is patented, before the patent expires. The patent owner can sue on the filing itself.
• Remedies, § 271(e)(4). The court orders that the FDA approval not take effect before the patent expires; may enjoin commercial manufacture, use or sale; and may award damages only if there has been commercial manufacture, use, offer, sale or importation. With a special injunction rule for biologics, these are the only remedies, apart from attorney fees under § 285.
• Declaratory judgment, § 271(e)(5). If the application includes a "paragraph IV" certification and neither the patent owner nor the brand application holder sues within 45 days after receiving notice, the applicant may seek a declaratory judgment that the patent is invalid or not infringed.

Sources: 35 U.S.C. § 271(e); Hikma Pharmaceuticals USA Inc. v. Amarin Pharma, Inc., No. 24-889 (U.S. June 4, 2026).

• § 271(f)(1) makes liable whoever supplies, or causes to be supplied, in or from the United States "all or a substantial portion of the components" of a patented invention, uncombined, in a way that actively induces their combination abroad in a manner that would infringe if done here. In Life Technologies v. Promega (2017) the Supreme Court held that "substantial portion" has "a quantitative, not a qualitative, meaning," and that § 271(f)(1) "does not cover the supply of a single component of a multicomponent invention."
• § 271(f)(2) covers supplying even one component that is especially made or adapted for the invention and not a staple article, knowing it is so made and intending that it be combined abroad in an infringing way.
• § 271(g) makes liable whoever, without authority, imports into the United States, or offers to sell, sells or uses in the United States, a product made by a process patented in the United States, during the process patent’s term. A product is no longer "made by" the process once it is materially changed by later processes or becomes a trivial and nonessential component of another product.

Sources: 35 U.S.C. § 271(f), (g); Life Technologies Corp. v. Promega Corp., 580 U.S. 140 (2017).

Section 282(b) lists the defenses that "shall be pleaded" in any action involving the validity or infringement of a patent:

• Noninfringement, absence of liability for infringement, or unenforceability (§ 282(b)(1)). A noninfringement defense argues that the accused product or process lacks at least one claim element, literally or by an equivalent, or that no single entity is responsible for every step of a method.
• Invalidity on any condition for patentability in Part II of the Patent Act, such as eligibility, novelty and nonobviousness (§ 282(b)(2)), or for failure to meet § 112 or § 251 (§ 282(b)(3)). Failure to disclose the best mode is not a basis for holding a claim invalid.
• Any other fact or act made a defense by the Patent Act (§ 282(b)(4)), such as the § 271(e)(1) safe harbor.

Invalidity is hard to prove in court. "A patent shall be presumed valid," each claim independently, and the burden rests on the challenger (§ 282(a)). The Supreme Court held in Microsoft v. i4i (2011) that § 282 requires an invalidity defense to be proved by clear and convincing evidence. A party relying on prior patents, publications or prior inventors must give notice of them at least 30 days before trial (§ 282(c)). Validity can also be challenged at the Patent Trial and Appeal Board; see the PTAB or district court comparison and IPR vs. PGR.

Patent exhaustion. Once the patent owner sells an item, the buyer and later owners may use or resell it without infringing. In Impression Products v. Lexmark (2017) the Supreme Court held "that a patentee’s decision to sell a product exhausts all of its patent rights in that item, regardless of any restrictions the patentee purports to impose or the location of the sale." Post-sale restrictions may still be enforceable as contracts, but not through an infringement suit.

Sources: 35 U.S.C. § 282; Microsoft Corp. v. i4i Limited Partnership, 564 U.S. 91 (2011); Impression Products, Inc. v. Lexmark International, Inc., No. 15-1189 (U.S. May 30, 2017); 35 U.S.C. § 271(e)(1).

A patent owner who proves infringement may obtain an injunction, which courts may grant "in accordance with the principles of equity" on reasonable terms (§ 283), and damages under § 284 of at least a reasonable royalty, possibly increased up to three times, plus attorney fees in exceptional cases under § 285. Damages are also limited by the six-year rule of § 286 and the marking rule of § 287. All of this is covered in our guide to patent damages. The latest infringement and remedies decisions are on our infringement and patent remedies topic pages.

Sources: 35 U.S.C. § 281; § 283; § 284; § 285; § 286; § 287.

• Comparing products instead of claims. Infringement turns on whether the accused product or process has each element of a claim, not on whether it resembles the patent owner’s product.
• Treating the doctrine of equivalents as a general "close enough" test. It applies element by element, may not erase an element, and is limited by prosecution history estoppel.
• Alleging inducement without a direct infringer. Inducement requires someone’s direct infringement; for a method split among parties, the steps must be attributable to one entity.
• Assuming awareness of the patent is enough for inducement. The defendant must know the induced acts infringe, and must take active steps to encourage them.
• Relying on a belief that the patent is invalid. It is no defense to inducement; invalidity must be proved by clear and convincing evidence in court.

Sources: Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997); Limelight Networks v. Akamai (2014); Akamai v. Limelight (Fed. Cir. 2015) (en banc); Commil v. Cisco (2015); Hikma v. Amarin (2026); Microsoft v. i4i (2011).