PATENTS - Canons of Construction

20 canons, which must be read in context of each other.  By then Judge, future Chief Judge, Michel.

(1) The intrinsic evidence comes first. (2) The most important intrinsic evidence is the words of the claims, both asserted and nonasserted. (3) The ordinary meaning usually applies. (4) However, the inventor can use terms in ways other than their ordinary meaning. (5) Technical terms are to be understood from the vantage point of the experienced worker in the field. (6) The specification must be consulted to see if words are being used other than with their ordinary meanings. (7) The specification acts as a dictionary if it defines terms expressly or by implication. (8) The specification is usually dispositive on claim construction issues. (9) Prosecution history may also be considered to construe claims. (10) Courts should not rely on extrinsic evidence to resolve ambiguities if intrinsic evidence will resolve them. (11) The public is entitled to design around an invention by determining its scope from the public record. (12) An interpretation that excludes the preferred embodiment is rarely correct and would require very strong evidence. (13) Resort to extrinsic evidence is proper when there is still an ambiguity after all of the intrinsic evidence has been considered. (14) Expert testimony that contradicts the intrinsic evidence is not entitled to any weight. (15) Extrinsic evidence means expert and inventor testimony, dictionaries, technical writings, and anything else that is outside the patent or its file history. (16) Extrinsic evidence may be used to help the court understand the claims but not change their meaning. (17) Expert testimony about the meaning of unambiguous claims is entitled to no weight. (18) Even when the patent is silent about meaning, the inventor's subjective intent about the meaning of the claims is entitled to no weight. (19) Technical treatises and dictionaries are a special case: the court may always consult them to understand the technology and to construe the claims, so long as no definition in the intrinsic documents is contradicted. (20) The prior art can be used to show how terms are understood by persons skilled in the art, except when that meaning is already clear from the intrinsic evidence.

 Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 39 U.S.P.Q.2d 1573 (Fed. Cir. 1996).