Constitutional objective “to promote the progress of science and useful arts.” Patent litigation is among the most complex areas of commercial litigation and is under the exclusive purview of the federal courts. It concerns the infringement of an invention, which is defined in the claims of a patent, which is granted by the US Patent & Trademark Office (USPTO) after examination by a patent examiner to determine the appropriate scope of the invention to define over that which came before the invention. Patent claims are crafted – often in what has been considered arcane and cryptic language – to describe the bounds of an invention over the prior art. Claim language is thus subject to difficult interpretation challenges. Despite the apparent strength of a patent claim, each patent infringement action is subject to defences; mostly noninfringement of the claims or invalidity of the claims. A patent litigation requires judges, juries and the lawyers to have or gain an understanding, at least to some level, of the subject technology and the federal patent laws. The technology may be quite complex and the laws are grounded in complex principles and procedures that in most jurisdictions require their own set of rules beyond the Federal Rules of Civil Procedure. The patent laws are so complex that Congress established a single appeals court – the Federal Circuit Court of Appeals – to bring consistency and a strong voice to the underlying principles. Thus, as companies develop products, some may exercise diligence by seeking a ‘freedom to operate’ opinion, also known as a ‘right to use’ opinion, from a competent patent attorney. An opinion may result from the knowledge of certain third-party patents. Ideally, however, an opinion should result from diligence investigations undertaken to locate previously unknown patents that may create an obstacle to the introduction of a product, process, pharmaceutical formulation or software. Freedom to operate investigations constitute diligence to measure and address the risk of an infringement action. Patent attorneys experienced in the technology and the law conduct research in the patent arts, focusing on the invention-defining claims of third-party patents. If the investigation reveals a patent with a scope that may cover the product, further investigation is undertaken to determine if a noninfringement defence exists. While a solid defence of noninfringement is enough to carry the day for an accused infringer, an investigation can continue to determine if the claims can be proven overly broad in light of the prior art and are thus invalid. Significantly, invalidity must be proven by clear and convincing evidence, which complicates the opinion and any ensuing litigation. Interestingly, an opinion of invalidity can prove useful in a post-grant proceeding put in place by Congress a decade ago – e.g. an inter partes review (IPR). While an IPR can be brought at any time, it is a tool most often employed by accused infringers as an adjunct to a patent 56 LAWYER MONTHLY SEPTEMBER 2023 Forced to creatively solve the problem of infringement, designers often find solutions that improve upon the original design.