In a patent infringement claim is one of the most common tactics taken is to assert that the patent is invalid. A patent can be considered invalid for a range of reasons for example lack of utility, incorrect inventorship, and fraud. In the 2011 court case, Microsoft v. i4i Limited Partnership, the Supreme Court addressed the issue of when a patent could be proved to be invalid. In this case the Supreme Court had to decide the type of burden of proof to claim the patent invalid. The Supreme Court found that patent invalidity standard is “clear and convincing evidence.” The Court also affirmed the Federal Circuit Court’s finding that “as for the finding of validity, Microsoft fails to establish that plaintiff’s invention would have been obvious to one of skill in the art, and there was sufficient evidence for a reasonable jury to find that it was not anticipated by another software program.” This case is important within the patent world because it sets for the standard of proof for invalidity.
 
Most patent lawsuits are won or lost on two defenses: invalidity or non-infringement. The reasons for invalidity. “An invalidity defense asserts that the patent holder did not satisfy the basic requirements to obtain a patent, usually because the claimed invention was not novel or would have been obvious when it was invented.” On the other hand, a non-infringement defense asserts that the defendant’s accused products or methods are not within the scope for the invention claimed within the patent. An invalidity defense asserts that even thought the USPTO granted the patent, it is invalid because the inventor failed to comply with the basic patentability requirements. The invalidity decision is based on the state of the world at the time the patent was granted. At the core of most invalidity challenges is whether the inventor has created something meaningfully new, novel, and nonobviousness meeting the 35 USC 102, and 103 requirements. These requirements ensure that patent is good for society, because society generally does not gain anything from something that already exists.
 
The other requirement inventors must meet is a fully disclosed invention so that someone skilled in the art can make the invention through the written description. The inventor must also give the best-mode, meaning the best way to create or build the invention. If these things are not met and the patent is issued there could be a invalidity claim brought against the patent. When writing a patent application, or when your patent attorney/agent is writing your application make sure you fully disclose the invention so that you meet all the requirements so that the possibility of someone raising an invalidity defense is less likely.
 
A non-infringement defense argues that even if a patent is valid, it does not cover what the accused infringer makes or does.” This scope is determined by the patent claims, which must point out and distinctly state what the invention is within the claims. A patent claim generally has two pieces: a preamble that sets forth the general description of the invention and a listing of the limitations of the invention which states the elements, steps, and/or relationships between the different pieces of the invention. “The accused product or process must satisfy every limitation of the claimed invention either literally or under the doctrine of equivalents to fall within the scope of the patent claim; if any limitation is not satisfied, there is no infringement.” Once a patent is issued, an inventor may not ever know if the patent will ever be challenged that is why it is important to mitigate the risk by making sure that you are following the rules laid out in 35 USC 101, 102, 103, and 112.