In most cases I believe validation and verification may be necessary especially in medical devices. Verification and validation together prove that a product is safe and that it meets its requirements, specifications, and is used as intended. The purpose of validation is to make sure the product meets its business needs from which the requirements were formed. Even in cases where validation isn’t required to be performed it would be a good idea to do so anyway because it offers another possibility to bring up an issue or defect before release.