The doctrine of equivalents is the alternative to proving a direct patent infringement. The plaintiff can use the doctrine to prove that although the product or process does not literally infringe on an existing patent, it contains identical elements to each of the elements claimed on the awarded patent. The test is whether the elements are substantially identical or equivalent so that the products or processes function the same or yield the same results. If a plaintiff can prove patent infringement, then he can seek injunctive relief, which includes removing the product from the marketplace or a court order to force the defendant to stop using a process. Compensatory damages are often also available as a legal remedy in those cases.
A patent for a product or a process consists of many claims that are shown by drawings. Individuals who own a patent are often protected by law against others who would copy those claims for use in their own products or processes. When there is lawsuit or investigation for patent infringement, the evidence reviewed are the claims filed with the awarded patent. The plaintiff’s first job is to prove that the party accused of patent infringement directly copied at least one of the claims of the approved patent. If the plaintiff cannot prove a direct infringement according to patent law, then she can show that one or more claims of the defendant’s patent are substantially identical to her patent, resulting in infringement under the doctrine of equivalents.
Determining whether claims are substantially identical is subjective and harder to prove than a direct patent infringement case. The functions, results, and the way that the process or product works is often examined to see whether the doctrine of equivalents applies. The testimony of expert witnesses is often used by both sides to argue or defend whether the claims are substantially identical or different. A jury or judge must often decide cases based on the expert witnesses and whom they believed the most. The reason being is that the claims can often involve technical and scientific matters that may exceed the knowledge base of the average juror.
One of the main objectives of the doctrine of equivalents is to stop individuals from cheating and benefiting from the work of those who file patents. There often would be no case against an infringer who tweaked the claims of awarded patents to avoid accusation of direct patent infringement. Individuals can often sue and be successful, even if there is no direct infringement, using the doctrine of equivalents in patent law.