A patent is a right granted by the federal government to an inventor to exclude others from making, using, or selling the patented invention. Patent litigation typically involves enforcement of the patent owner’s “right to exclude” against an accused infringer. In some cases, a person who feels threatened by a patent owner will file a lawsuit against the patent owner seeking a declaration that the patent is not infringed or that the patent is invalid.

Infringement and validity are the two primary issues at stake in patent litigation and both issues are determined by the “claims” of the patent – short paragraphs which specifically define the limits of patent coverage. The patent owner bears the burden of proving infringement. A patent is infringed if the accused infringer’s product or activities fulfill all elements of at least one claim of the patent. Patents are assumed to be valid, thus the accused infringer bears the burden of proving that the patent is invalid (or unenforceable). A patent is invalid if the invention described in the claims is shown by “prior art” to be neither new nor “unobvious.” Prior art is the entire body of knowledge in the field of the invention existing as of the date of the invention.

An important stage unique to patent litigation is the “claim construction” phase. Since the claims are all-important in patent litigation, the judge is charged with interpreting the claims, putting the often stilted, formalistic claim language into words more understandable to a lay jury. The claims as construed by the judge thereafter govern infringement and validity. Patent owners often seek a broad claim construction so as to cover the accused infringer’s activities. However, a broad construction of the claims make them more susceptible to being found invalid over prior art ferreted out by the accused infringer. Interpretation of the claims can be determinative of the lawsuit, and cases are often settled at this stage.

If the patent is found to be infringed, the owner of an infringed patent is entitled to compensatory damages (no less than a reasonable royalty) and the infringer is often enjoined from further infringing activities. However, by bringing suit the patent owner risks that the patent will be found to be invalid.

Patent litigation is high-stakes, complex litigation and can be quite expensive. According to the 2009 Economic Survey conducted by the American Intellectual Property Law Association, the total cost of a patent lawsuit can range between a median low of $650,000 to a median high of $5.5 million. Use of expert witnesses is very common. Patent litigators, or litigation teams, combine excellent litigation skills and a keen understanding of patent law.

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