Although not intended as guidance for internal auditors, the IAF Auditing Practice Group Guidance on Auditing Competence recommended this:
When an auditor needs answer for this question:
Are competent people assigned to those workplace activities necessary to control the quality characteristics of its processes and products?
Guidance:
Verify that some form of evaluation process is in place to ensure that the competencies are appropriate to the organization's activities, and that the persons selected as competent are demonstrating these competencies. Also, the process should ensure that any deficiencies are being acted upon and the effectiveness of persons is being measured. Verify that the activities that affect quality are performed by persons selected as competent. Evidence may be obtained throughout the audit with an emphasis on those processes, activities, task and products where human intervention may have the greatest impact. The auditor may review job descriptions, testing or inspection activities, monitoring activities, records of management reviews, definition of responsibilities and authorities, nonconformity records, audit reports, customer complaints, processes validation records etc.
See this
link.