Can a lack of best mode be used to invalidate a patent claim under current law?

Under current patent law, specifically following the America Invents Act (AIA) and subsequent interpretations, the lack of best mode cannot be used as a basis for invalidating a patent claim. The best mode requirement, which mandates that an inventor disclose the preferred method of practicing the invention, is no longer enforceable in a way that can lead to invalidation. While an applicant must disclose the best mode to comply with the requirements of the Patent Act when filing a patent application, failure to do so does not provide grounds for challenging the validity of an issued patent.

This change reflects a shift in policy where the emphasis has moved away from the best mode requirement as a critical factor in evaluating patentability. As a result, even if a patent is found to lack a disclosed best mode, it remains valid and enforceable, allowing inventors to maintain their intellectual property rights without the risk of invalidation on this specific ground.