In the 1998 case of Wayne K. Pfaff v. Wells Electronics, Inc., the U.S Supreme Court ruled on an issue related to patent law and its "on-sale" bar provision. The court held that a product could be considered "on sale," even if it had not yet been manufactured or fully detailed in writing, as long as there was evidence that it was more than just a concept at the time of sale. This ruling came about after Wayne Pfaff attempted to sue Wells Electronics for patent infringement over his invention of a new type of computer chip socket two years after he sold blueprints for its design but before he applied for a patent. The court found against Pfaff because his invention was already on sale more than one year prior to his application date, thus violating Section 102(b)’s “on-sale” bar rule under US Patent Law.

In the dissenting opinion for Wayne K. Pfaff v. Wells Electronics, Inc., Justice Stevens argued that the majority's decision to invalidate Pfaff's patent because of a sale made before he applied for it was inconsistent with previous court rulings and could potentially harm inventors who need time to perfect their inventions before applying for patents. He believed that an invention is not "on sale" until it has been reduced to practice, meaning it works for its intended purpose. In this case, although Pfaff had sold his invention prior to filing a patent application, he hadn't yet built or tested a prototype at the time of sale - hence according to Justice Stevens' interpretation of 'reduced-to-practice', the on-sale bar should not apply here. The dissent further criticized the new rule established by majority as being too rigid and failing in providing clear guidance about when an inventor must file a patent application after making sales related to their invention.