What is Patent Infringement?

Key Facts

• Statute: 35 U.S.C. § 271 defines infringement; §§ 283 to 285 set remedies
• All-elements rule: A product infringes a claim only if it contains every element of that claim, literally or by an equivalent
• Strict liability: Direct infringement does not require intent or knowledge; knowledge matters for indirect infringement and for enhanced damages
• Damages window: Recovery is limited to infringement within the 6 years before the complaint, under § 286
• Marking: Without patent marking or actual notice, damages for a product patent begin only when the infringer is notified
• Where cases are filed: US district courts, with the International Trade Commission as an alternative for imported goods

Types of Infringement

• Direct infringement (§ 271(a)): Performing every element of a claim yourself
• Induced infringement (§ 271(b)): Knowingly encouraging another to infringe, for example through instructions or marketing
• Contributory infringement (§ 271(c)): Selling a component with no substantial non-infringing use, knowing it is made for an infringing product
• Literal infringement: The accused product matches each claim element exactly
• Doctrine of equivalents: An element is met by something that performs substantially the same function in substantially the same way to reach the same result, limited by prosecution history estoppel
• Willful infringement: Deliberate or reckless infringement of a known patent, which can support up to treble damages under § 284

The Analysis

Infringement is decided in two steps. First the court construes the claims, then the fact-finder compares the construed claims to the accused product. Both sides build claim charts that walk through each element. Method claims are infringed only when every step is performed, and, for divided infringement, only when one party directs or controls all of them.

Defenses

1. Non-infringement: At least one claim element is missing from the accused product
2. Invalidity: The claims are anticipated or obvious over prior art, lack written description or enablement, or claim ineligible subject matter; validity can also be challenged at the Patent Trial and Appeal Board through inter partes review
3. Unenforceability: Inequitable conduct during prosecution, or a broken terminal disclaimer common-ownership requirement
4. License or exhaustion: The accused party has a license, or the product was sold with the patent owner's authorization
5. Prior commercial use: Under § 273, a party that commercially used the invention more than a year before the patent's filing date
6. Expired patent or unpaid maintenance fees

Remedies

A prevailing patent owner can obtain damages adequate to compensate for the infringement, no less than a reasonable royalty, and lost profits where they can be proven. Injunctions are available but, since eBay v. MercExchange in 2006, are not automatic and are rarely granted to non-practicing entities. Attorney fees can be awarded in exceptional cases. For companies on either side, litigation intelligence on which patents are being asserted, by whom, and with what outcomes is the starting point for both risk assessment and enforcement planning.