The red team and blue team should not share supervisors.

Nor, in the case of QA, should the audit team be engineers trained to act and think like the ones who wrote the software. A fresh perspective is useful.

But in the long run, supervisory independence is the real deal. I know of a QA manager who shut down an entire factory's output until a major safety issue (that had been kicked down the road several times) was addressed. It took chutzpah, and serious power, to do that. The Dir. of Engrg. would NEVER have allowed it.