In some professions people are supervised by externals. This is a good thing as it means they can be much more honest and less guarded instead of fearing that their managers will use info against them. It is a much more healthy environment for clinical supervision to take place IMO/E. The relationship between practitioner and superviser is an important one and unnecessary hierarchies and fear of repercussion can get in the way. Performance reviews are a different thing and simply calling it supervision isn't enough, unfortunately I think there is a tendancy for some organisations to try to keep supervision inhouse and in doing so they don't create the cynamic for people to be properly supervised.