I have found many NC's are written not for lack of evidence but rather the people being interviewed did not know the answer. A short story..... I once was a recipient of a customer audit that the previous QM received 48 CA on. After reviewing the report I was able to get the customer to rewrite the report voiding 41 of the 48. While the customer was glad things were actually in place they were not that the QM did not know the system nor bothered to ask those that did.