Literal Infringement

Literal infringement occurs when an accused product or process contains every element of a patent claim, as those elements are construed by the court. The analysis is textual — does the accused product literally (directly) satisfy each claim limitation? Literal infringement does not require intent; making, using, selling, offering to sell, or importing an infringing product constitutes infringement under 35 U.S.C. § 271(a) regardless of whether the infringer knew about the patent. Literal infringement requires NO approximation — the accused product must exactly satisfy each limitation as construed. If even one claim element is absent, there is no literal infringement of that claim, though doctrine of equivalents may still apply.

The all-elements rule (also called the all-limitations rule) requires that for a patent claim to be infringed — literally or under the doctrine of equivalents — every element (limitation) of the claim must be found in the accused device or method. The rule applies to BOTH literal infringement (every element must be literally present) and the doctrine of equivalents (every element must be literally present OR present by equivalence). Consequences: (1) a defendant can defeat infringement by showing even one claim element is absent; (2) the patent owner cannot prove infringement by showing the accused product is 'similar' overall — similarity is irrelevant; the element-by-element comparison controls; (3) a single, cleverly missing element can design around a patent even when the accused product is substantively identical in purpose. The all-elements rule prevents the doctrine of equivalents from eliminating all claim limitations.

Claim construction — how the court interprets each claim term's meaning — determines whether the accused product satisfies each limitation and is therefore the threshold question in every infringement analysis. The process: (1) The court construes each claim term through a Markman hearing (claim construction hearing), using intrinsic evidence: the claims themselves, the specification, and prosecution history; (2) Extrinsic evidence (expert testimony, dictionaries) is consulted only if the intrinsic record is ambiguous; (3) The construed claim is then compared to the accused product element by element. Practical significance: a narrow construction (limiting a claim term to a specific embodiment) makes literal infringement harder to prove; a broad construction makes it easier. Claim construction is reviewed de novo by the Federal Circuit (Teva Pharmaceuticals v. Sandoz, S.Ct. 2015: underlying factual findings are reviewed for clear error, but legal conclusions de novo).

LITERAL INFRINGEMENT: the accused product contains the exact element required by the claim, as construed. No approximation, no functional equivalence — the element is literally present. DOCTRINE OF EQUIVALENTS (DOE): the accused product does not literally satisfy a claim element, but the element performs substantially the same function, in substantially the same way, to achieve substantially the same result (function-way-result test from Graver Tank). Key differences: (1) PROSECUTION HISTORY ESTOPPEL limits DOE — if the applicant narrowed a claim limitation by amendment or argument, DOE cannot recapture the surrendered scope for that element (Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., S.Ct. 2002); (2) LITERAL INFRINGEMENT is not subject to prosecution history estoppel; (3) DOE is an equitable doctrine — courts balance the protection it provides with the notice function of claims; (4) DOE analysis is applied element by element, not to the claim as a whole.

Yes — this is fundamental to patent claim structure. An accused product may infringe an independent claim (broader) but not a dependent claim (narrower) that adds a limitation the accused product lacks. Example: if Independent Claim 1 requires 'a device with A and B,' and Dependent Claim 2 requires 'the device of Claim 1, further comprising C,' a product with A and B but not C infringes Claim 1 but not Claim 2. Strategically, this means: (1) patent owners benefit from having broad independent claims that cover core technology plus narrow dependent claims that cover specific valuable embodiments; (2) defendants often design around by avoiding just the additional element of a specific claim; (3) invalidity of a dependent claim does not automatically invalidate the independent claim from which it depends (though invalidity of an independent claim renders all claims depending from it invalid). The doctrine of claim differentiation supports broad readings of independent claims by assuming dependent claims add meaningful limitations.