In order to be held as a direct infringer of a United States patent under 35 USC § 271(a), it is necessary during the life of the patent to have made, used, offered to sell [182] or sold what is claimed in the patent within the United States or to have imported the patented invention into the United States. Under this test one can be liable for patent infringement even though one was unaware of the patent or that the acts one is carrying out are tortious. [183] Furthermore it has long been the law that one does not have to sell the product one produces to be an infringer of a patent, mere manufacture, at least if for a commercial purpose will suffice. The possibility of suit against someone offering a product for sale was added to the statute as part of the Uruguay Round Amendments Act, taking effect on January 1, 1996. If the offer for sale originates from the United States there may be an infringement even if the physical embodiment never enters the United Sates as was the case in Halmar Robicon Group v. Texas Instruments [184] where a letter making an offer for sale originated in Texas but the goods in question were made in Japan and shipped direct to a customer in Canada. It appears that the term “offer for sale” in this context may have a broader meaning than is normal in contract law and may include acts that a contract lawyer would find to be merely an invitation to make an offer. [185] It seems clear, however, that an uncompleted offer to donate an alleged infringing article is not an infringement. [186]

Limited use of an invention for non-commercial experimental purposes may, however, be permissible without being an infringement. To succeed with such a defense, it is however, necessary that the use be of an entirely non-commercial nature. [187]