Doctrine

The substantive rules that decide patent cases — how claims are read, what counts as infringement, what makes a patent valid, what defenses are available, and what a patentee can recover. Each entry traces the rule to its statutory source and the decisions that gave it shape.

Infringement

What the accused product or method must do — or be made to do — to fall within the patent's reach.

• Claim construction (Markman)The court's threshold task. Phillips v. AWH governs the hierarchy of intrinsic over extrinsic evidence.
• Literal infringement35 U.S.C. § 271(a). Every limitation of the construed claim must read on the accused product.
• Doctrine of equivalentsFunction-way-result; insubstantial differences. Bounded by Festo and the all-elements rule.
• Direct infringementStrict liability under § 271(a). Divided infringement after Akamai v. Limelight (2015).
• Induced and contributory infringement§ 271(b)–(c). Knowledge required after Global-Tech and Commil.

Validity

The grounds on which an issued patent can be set aside, and the burdens that govern the inquiry.

• Subject matter eligibility under § 101The Alice/Mayo two-step. Abstract ideas, laws of nature, and the unsettled post-Alice landscape.
• Anticipation under § 102A single prior-art reference disclosing every limitation. Pre- and post-AIA differences.
• Obviousness under § 103Graham factors with secondary considerations. KSR rejected the rigid TSM test.
• Written description and enablement§ 112(a). Possession test (Ariad) and the Wands enablement factors. Amgen v. Sanofi reshaped genus-claim enablement.
• Definiteness under § 112(b)Reasonable certainty after Nautilus. Means-plus-function under § 112(f) post-Williamson.

Defenses

Equitable bars and prosecution-related limits on enforcement.

• Inequitable conductTherasense raised the bar to but-for materiality plus specific intent. Egregious-misconduct exception remains.
• Prosecution history estoppelFesto's presumption of surrender; tangential, unforeseeable, and other-reason rebuttals.
• On-sale barPfaff's two-prong test. Helsinn confirmed AIA on-sale bar reaches confidential sales.
• Public use barEgbert v. Lippmann's "in public use" still controls. Experimental-use exception narrow.
• Patent exhaustionImpression Products extended exhaustion to international authorized sales.

Damages and remedies

What a successful patentee can recover, and what conduct triggers enhancement, fees, or an injunction.

• Reasonable royalty§ 284's statutory floor. Georgia-Pacific factors and the hypothetical negotiation. Apportionment and SSPPU.
• Lost profitsPanduit's four-factor test; price erosion; convoyed sales after Rite-Hite.
• Willfulness and enhanced damagesHalo replaced Seagate. Subjective recklessness; preponderance; up to treble damages.
• Attorneys' fees under § 285Octane's totality test. Highmark's abuse-of-discretion review on appeal.
• Permanent injunctionseBay's four-factor equitable test ended the categorical injunction rule.