A patent infringement case can be filed in any district in the United States that has personal jurisdiction over the defendant, which may include those states or districts where the defendant’s products are sold but where the defendant may not have offices. The likelihood of one party or the other prevailing in the litigation varies depending on the district in which the action is filed. The venue for a district court patent case impacts how quickly the case moves, the likelihood that it will be resolved prior to trial, and the jury composition at trial. Patent holders thus often choose the place of the litigation based on a belief that one forum or another is generally more favorable to patent holders. Parties accused of infringement may seek transfer of a district court patent case to their “home” district, if they can show that is the logical place to site the trial. In addition, if a patent holder has threatened a company or its customers with an infringement action, that company may be able to preemptively file suit for “declaratory judgment,” namely a judgment from the court declaring the patent invalid, unenforceable, or not infringed. Such a suit can be filed if the controversy between parties is of sufficient immediacy and reality to warrant the attention of the court. An action for declaratory judgment may be brought in any district where there is personal jurisdiction over the patent holder. Personal jurisdiction over the patent holder is not found in the district where the declaratory judgment plaintiff resides or has a principal place of business simply because the patent holder has sent a letter there about the patent. Rather, personal jurisdiction only exists where the defendant has established “minimum contacts,” which can be established by selling products or conducting business in the forum.