Modern machine safety standards (eg. AS 4024.1-2019, EN ISO 13849.1, AS 62061) require that a safety system design shall be validated by a knowledgeable person not involved in the original design.
This is a logical step to verify that the designer’s solution does in fact meet the requirements of the safety specification and requires an analysis of all the design information, assumptions, fault considerations and exclusions and/or testing of final installation.