Determining whether a patent is infringed is a question of fact1 for a jury and frequently a difficult one. juries are generally asked to determine, first, whether there is literal infringement, and second, whether there is infringement under the doctrine of equivalents. A finding of either type of infringement is sufficient to render the accused party liable. juries frequently become confused in patent cases involving "means-plus-function" claims. The confusion stems from the fact that under 35 U.S.C. § 112, determining literal infringement of a means-plus-function claim requires the jury to determine whether the accused product is equivalent to the subject matter disclosed in the patent. The subsequent determination of infringement under the doctrine of equivalents also requires the jury to determine whether the accused product is an equivalent. The question that arises, then, is whether an "equivalent" under § 112 is the same thing as an "equivalent" under the doctrine of equivalents. In other words, is there one type of equivalence or two?
According to the Federal Circuit, the expert court in patent law, the general rule is that there is only one type of equivalence. There are, however, two exceptions2 under which an accused product may be an "equivalent" for doctrine of equivalents purposes (resulting in infringement by equivalence) and yet not be a § 112 "equivalent" (resulting in no literal infringement). In cases involving one of those two exceptions, the accused product cannot be equivalent under § 112, but the jury must still determine whether the accused product is nevertheless equivalent under the doctrine of equivalents. In cases involving neither exception, a finding of equivalence requires evidence of both literal infringement under § 112 and infringement under the doctrine of equivalents, while a finding of no equivalence should result in no infringement at all. Outside of the two exceptions, therefore, a jury should never say "no" to literal infringement and "yes" to infringement under the doctrine of equivalents.
And yet, juries return verdicts finding exactly that. Recent verdicts indicate the problem is current and ongoing.3 These verdicts demonstrate juries' misunderstanding of the law. Sometimes the erroneous verdict is corrected by the district court, and sometimes the Federal Circuit has to set things right on appeal. Regardless of whether the jury alone was confused, or whether the district court was also mistaken, there exists a common failure to communicate to juries a statement of the law that is both clear and correct. This failure has the potential to seriously harm defendants in patent infringement cases involving means-plus-function claims because, as this Comment will demonstrate, where a jury's confusion regarding the notion of equivalence leads to simultaneous findings of no literal infringement but infringement under the doctrine of equivalents, that second finding may be incorrect as a matter of law, and the defendant may be wrongly held liable for infringement.
This Comment proposes jury instructions designed to clearly and correctly state the law and lead a jury to reach a correct verdict based on its determinations of fact. The instructions allow a jury the discretion to which it is entitled in determining questions of fact, while at the same time precluding the jury from returning a verdict that is incorrect as a matter of law once the jury has made its factual determinations. Following this Introduction, Part II explains several patent law fundamentals, including the legal standards for finding literal infringement and infringement under the doctrine of equivalents. Part II also explains the meanings of means-plus-function claims and the standards for infringement. Part III demonstrates how jury confusion regarding equivalence can lead to verdicts that are incorrect as a matter of law and harmful to both defendants and plaintiffs. Part III also provides two examples of recent cases in which juries reached incorrect verdicts due to confusion about the term "equivalence" in connection with literal infringement under § 112 and infringement under the doctrine of equivalents. …