Why is the "Professional Standards division" a division of the force? In New Zealand the equivalent organisation is very specifically NOT part of any police fo

Why is the "Professional Standards division" a division of the force? In New Zealand the equivalent organisation is very specifically NOT part of any police force. In fact, it's in their name: "Independent Police Conduct Authority". Maybe that's one reason why New Zealand is usually in the top five "least corrupt countries in the world". The USA isn't. This is one reason why.