I would make a brief answer to the question with respect to the chain of command.
The chain of command does not answer the important issues. A police agency that has vested resources in a particular investigation may be particularly poorly suited to make important decisions with respect to whether or not proper balances have been met. The law now requires that if the police wish to take the impression of a hand from an individual, or install a tracking device on an individual's car, both of which seem relatively innocuous, prior judicial authorization is required for both of those.
The independence of the judiciary enables them to make proper decisions about when to use and when not to use these techniques. If prior judicial authorization is needed before the police can follow a car through electronic surveillance, then presumably it should also be used before it is determined that the police are permitted to commit an assault because the demands of a particular investigation might require it.