Food for thought for this weighty debate.
ISO/TS 9002 published November 1st 2016. Quality Management System Guidance for the Implementation of ISO 9001:2015
Yes, it says guidance, but it was published by TC 176, The introduction starts out with "This document has been developed to assist users to apply the quality management system requirements of ISO 9001:2015 Quality management systems – Requirements."
The format follows the same numbering system as ISO 9001:2015, and here is what we find in the fourth paragraph of 9.2.2:
"When assigning persons to conduct audits, the organization should ensure objectivity and impartiality of the audit process. In some cases, specifically in smaller organizations or areas of the organization where specific job knowledge is required, it can be necessary for a person to audit their own work. In this situation, the organization might have the internal auditor work with a peer, or have the results reviewed by a peer or a manager, to ensure results are impartial. The organization could also consider obtaining resources from an external provider such as a university, external auditor, or another organization."
Now for my comments. To say that you cannot be impartial and objective and audit your own work is really arrogant. I will agree that not everyone could. I might say that two important factors would be the integrity of the individual and the culture of the company. Both are topics that an auditor would likely be hard pressed to challenge.
This guidance provides possible methods to be used to ensure impartiality and objectivity. It is also common sense.
Flame suit on.