patent infringement
Patent infringement is the unauthorized violation of an exclusive right granted by a U.S. patent. It may be direct or indirect. Under 35 U.S.C. § 271(a), direct infringement includes making, using, offering to sell, or selling a patented invention within the United States, or importing the patented invention into the United States, during the patent term. Direct infringement generally does not require proof that the defendant intended to infringe or copied the patent. In Commil USA, LLC v. Cisco Systems, Inc., 575 U.S. 632 (2015), the U.S. Supreme Court described direct infringement as a strict-liability offense.
A patent gives its owner a right to exclude others, not necessarily an affirmative right to make or use the invention. An invention may itself fall within an earlier unexpired patent. The U.S. Patent and Trademark Office (USPTO) issues patents and conducts certain post-issuance proceedings, but it does not decide whether a patent has been infringed.
Patent claims define the protected scope. In Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996), the Supreme Court held that construing claim terms is for the court. After claim construction, the accused product or process is compared with the asserted claims. Literal infringement generally requires every limitation of at least one asserted claim to be present in the accused product or process. A patent can also be infringed under the doctrine of equivalents when an accused element is equivalent to a claimed element even though the claim is not satisfied literally. Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997), requires an element-by-element inquiry and recognizes limits such as prosecution-history estoppel.
Section 271 also recognizes indirect infringement. A person who actively induces another's infringement may be liable under § 271(b). Inducement requires an underlying act of direct infringement and knowledge of the patent and that the induced acts constitute infringement. Contributory infringement under § 271(c) can arise when a person offers to sell or sells within the United States, or imports into the United States, a component constituting a material part of the patented invention, knowing that the component was especially made or adapted for an infringing use, if the component is not a staple article or commodity suitable for substantial noninfringing use. Commil USA, LLC v. Cisco Systems, Inc., 575 U.S. 632 (2015), explains the different mental-state rules for direct and induced infringement. In Hikma Pharmaceuticals USA Inc. v. Amarin Pharma, Inc., 146 S. Ct. 1391 (2026), the Supreme Court unanimously held that an inducement complaint must plausibly allege that the defendant actively encouraged infringement, not merely that others could plausibly read the defendant's statements as encouraging infringement.
An accused infringer may assert noninfringement, absence of liability, invalidity, or unenforceability under 35 U.S.C. § 282. An issued patent is presumed valid, but particular claims may be held invalid if statutory patentability requirements were not met. Other defenses and statutory exceptions may apply to particular activities.
If infringement is proven, 35 U.S.C. § 284 requires compensatory damages of at least a reasonable royalty, and the court may increase damages in appropriate cases. A court may also grant an injunction under § 283 according to equitable principles. In eBay Inc. v. MercExchange, L.L.C., 547 U.S. 388 (2006), the Supreme Court held that a permanent injunction is not automatic after infringement; the traditional four-factor equitable test applies.
[Last reviewed in August of 2026 by the Wex Definitions Team]
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