Types of Patent Infringement

Common situations.

• A company is told its product infringes a patent it has never seen.
• A software provider is accused because its customers run the claimed method.
• A generic drug maker is accused of inducing doctors to prescribe for a patented use.
• A parts supplier is accused because its component goes into an infringing machine.

Direct infringement: literal.

Whoever, without authority, makes, uses, offers to sell, sells, or imports a patented invention in the United States during the patent term infringes (35 U.S.C. § 271(a)). The test has two steps: the court decides what the claims mean, then the fact-finder compares the accused product with the claims as construed.

A product infringes literally only if it contains every element of at least one claim. Missing one element defeats literal infringement of that claim, no matter how similar the products are otherwise. Adding extra features does not avoid infringement.

Direct infringement is strict liability. Good faith, independent development, and ignorance of the patent are not defenses to liability, though they matter to willfulness and damages.

Direct infringement: the doctrine of equivalents.

A product that does not meet a claim element literally can still infringe if it has an equivalent of that element. The usual tests ask whether the difference is insubstantial, or whether the substitute performs substantially the same function in substantially the same way to reach substantially the same result (Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17 (1997)). The comparison is made element by element, not for the product as a whole.

Three rules limit the doctrine:

• All-elements rule. An equivalent cannot erase a claim element entirely (Warner-Jenkinson).
• Prosecution history estoppel. A patent owner who narrowed a claim to win the patent is presumed to have surrendered the territory between the original and the narrowed claim (Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002)).
• Dedication-disclosure. Subject matter disclosed in the specification but not claimed is dedicated to the public and cannot be recaptured through equivalents (Johnson & Johnston Assocs. v. R.E. Serv. Co., 285 F.3d 1046 (Fed. Cir. 2002) (en banc)).

An equivalents theory also cannot cover what was already in the prior art.

Method claims and divided infringement.

A method claim is infringed only when every step is performed. When different parties perform different steps, the steps of others count against one party only if it directs or controls their performance, or if the parties form a joint enterprise (Akamai Techs., Inc. v. Limelight Networks, Inc., 797 F.3d 1020 (Fed. Cir. 2015) (en banc)). Directing or controlling can be shown where a party conditions a benefit on performing the steps and sets their manner or timing. There is no inducement unless someone is liable for direct infringement (Limelight Networks, Inc. v. Akamai Techs., Inc., 572 U.S. 915 (2014)).

This matters most for software and internet services, where the provider and its users each perform part of a method.

Induced infringement.

Whoever actively induces infringement is liable as an infringer (§ 271(b)). The patent owner must prove:

1. Someone directly infringed.
2. The accused party took active steps to encourage that infringement, such as instructions, advertising, or product design.
3. The accused party knew of the patent and knew the induced acts infringe. Willful blindness can satisfy this (Global-Tech Appliances, Inc. v. SEB S.A., 563 U.S. 754 (2011)).

A good-faith belief that the patent is invalid is not a defense to inducement, though a good-faith belief of noninfringement can be (Commil USA, LLC v. Cisco Sys., Inc., 575 U.S. 632 (2015)).

The 2026 pleading standard. In Hikma Pharmaceuticals USA Inc. v. Amarin Pharma, Inc., No. 24-889 (U.S. June 4, 2026), a unanimous Supreme Court held that an inducement complaint must plausibly allege that the defendant took active steps to encourage the infringing use. A generic drug label that omitted the patented use, combined with statements that the product was a "generic version" of the brand drug, was not enough. The decision arose under the Hatch-Waxman scheme but applies the general § 271(b) standard, so defendants in other industries now cite it in motions to dismiss. See Pleadings and Early Motions.

Contributory infringement.

Whoever sells, offers to sell, or imports a component of a patented invention, knowing it is especially made or adapted for use in infringement and is not a staple article suitable for substantial noninfringing use, is liable as a contributory infringer (§ 271(c)). As with inducement, there must be a direct infringement and knowledge of the patent (Aro Mfg. Co. v. Convertible Top Replacement Co., 377 U.S. 476 (1964)).

The key fight is usually whether the component has a substantial noninfringing use. If it does, contributory infringement fails, though inducement may still apply.

Infringement that crosses borders.

Patents are territorial, but three provisions reach conduct tied to other countries:

• Importation of an infringing product is direct infringement (§ 271(a)).
• Products made abroad by a patented process infringe when imported, sold, or used here, unless materially changed or a trivial part of another product (§ 271(g)).
• Components shipped abroad for assembly into an invention can infringe (§ 271(f)). Supplying a single component of a multicomponent invention does not violate § 271(f)(1) (Life Techs. Corp. v. Promega Corp., 580 U.S. 140 (2017)). A patent owner who proves a § 271(f)(2) violation can recover foreign lost profits (WesternGeco LLC v. ION Geophysical Corp., 585 U.S. 407 (2018)).

Generic drugs and biosimilars.

Filing an application with the FDA to market a generic drug or biosimilar before a patent expires is an act of infringement, even though nothing has been sold (§ 271(e)(2)). This creates a lawsuit before launch. See Hatch-Waxman and Biosimilar Litigation.

Design patents.

A design patent is infringed if an ordinary observer, familiar with the prior art, would be deceived into thinking the accused design is the same as the patented design (Egyptian Goddess, Inc. v. Swisa, Inc., 543 F.3d 665 (Fed. Cir. 2008) (en banc)). A design patent owner may recover the infringer's total profit on the "article of manufacture" (35 U.S.C. § 289), which may be a component rather than the whole product (Samsung Elecs. Co. v. Apple Inc., 580 U.S. 53 (2016)).

Texas notes.

• Most Texas patent suits are filed in the Eastern and Western Districts of Texas, which have local patent rules setting early deadlines for infringement contentions. Those contentions must chart each accused product against each asserted claim. See Local Patent Rules.
• Infringement is decided only in federal court (28 U.S.C. § 1338(a)). Texas state courts may decide contract and ownership disputes that touch patents.

Sources.

• 35 U.S.C. §§ 271, 289.
• Hikma Pharms. USA Inc. v. Amarin Pharma, Inc., No. 24-889 (U.S. June 4, 2026).
• Akamai Techs., Inc. v. Limelight Networks, Inc., 797 F.3d 1020 (Fed. Cir. 2015) (en banc).
• Limelight Networks, Inc. v. Akamai Techs., Inc., 572 U.S. 915 (2014).
• Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17 (1997).
• Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002).
• Johnson & Johnston Assocs. v. R.E. Serv. Co., 285 F.3d 1046 (Fed. Cir. 2002) (en banc).
• Global-Tech Appliances, Inc. v. SEB S.A., 563 U.S. 754 (2011).
• Commil USA, LLC v. Cisco Sys., Inc., 575 U.S. 632 (2015).
• Aro Mfg. Co. v. Convertible Top Replacement Co., 377 U.S. 476 (1964).
• Life Techs. Corp. v. Promega Corp., 580 U.S. 140 (2017).
• WesternGeco LLC v. ION Geophysical Corp., 585 U.S. 407 (2018).
• Egyptian Goddess, Inc. v. Swisa, Inc., 543 F.3d 665 (Fed. Cir. 2008) (en banc).
• Samsung Elecs. Co. v. Apple Inc., 580 U.S. 53 (2016).

This guide is general information, not legal advice. Law checked through October 20, 2026. See the Disclaimer.