The patent system fosters invention, disclosure, and innovation by temporarily protecting the fruits of a patentee’s labor. As an expansion of patent rights, the doctrine of equivalents provides a patentee with the ability to recover for patent infringement by a device that is equivalent, but not identical, to a patent claim. Means-plus-function patent claims under 35 U.S.C. § 112, ¶ 6 permit a patentee to describe, in her claim, the function of an element of her invention, without specifying the structure of the element. However, the application of the doctrine of equivalents to means-plus-function claims has resulted in inconsistent and inefficient infringement analyses that may harm either the plaintiff or the defendant. This note explains the basics of patent law and the heart of the confusion about the doctrine of equivalents and means-plus-function claims. The author evaluates four approaches to the doctrine of equivalents and means-plus-function claims, concluding that the Temporal Predetermination Approach best preserves the goals of each theory of patent infringement while promoting consistency and efficiency. Ultimately, the author proposes changes in jury instructions, the use of a specified set of special jury verdicts, and changes in § 112, ¶ 6 to clear the confusion and provide consistent, efficient infringement judgments.
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