A huge chunk of legal theory is about negating conflicts of interest.
https://en.wikipedia.org/wiki/Conflict_of_interest
From Judicial Disqualification, to the very core of our adversarial judicial system (Fruit of the Poisonous tree, etc. etc.), it is definitely a well studied subject in the US.
The solution is pretty simple. If someone in power has a conflict of interest, then the law should be rewritten to resolve it. Typically, the US seems to do it by introducing an adversary of some kind. (ie: The NYPD are considered 'corrupt' behind the 'Blue Wall of Silence'. So an adversary has been introduced: the Civilian Complaint Review Board. The Civilian Complaint Review Board not only reviews complaints, but has been granted judicial power to subpoena individual officers and force them to testify before court)
In fact, our very constitution was designed around this principle.
* The President enforces laws, but is not allowed to write the laws.
* The Congress writes the laws, but cannot enforce the law. Congress is further divided into two different houses (Senate and House) with differing responsibilities, as writing the law is considered the most powerful position of this country. Only when both chambers agree do laws move forward.
* When questions of enforcement come into play, the Judicial branch resolves it by interpreting the laws.
-------
Unfortunately, large swaths of red tape and political theory dance is expensive. So even the Federal Government cuts corners sometimes... but even more so with local governments.
When some country town can only afford one Sheriff for their entire police department (which is a huge chunk of the country btw), I'm gonna bet you that the town won't be able to afford a "Civilian Complaint Review Board" like New York City can.
A good example is St. Louis County / Ferguson right now. Their Police Department has been shown to be incompetent at best. But they can't even afford Police Cameras! They tried to buy cameras this past year, and the only way they were able to afford cameras was through funds seized from the populace (either traffic fines or other sources...). Such a source of money isn't enough to handle the ongoing storage costs of police cameras. (To say nothing about the conflicts of interest involved in a Police Force with guns who rely on parking tickets, fines, and court fees to fund key parts of their department...)
So Ferguson / St. Louis County will remain in the dark, without police cameras... at least until that city / county can afford them.
Still... Ferguson and St. Louis County are learning. They are probably going to implement civilian review boards soon. http://www.stltoday.com/news/local/govt-and-politics/ferguso...
But for a county that can't even afford police cameras properly, I bet you that the rollout of this new agency will be slow at best.