Quis custodiet ipsos custodes? It might have to be Federal, but not the Justice Department. And frankly that function should not even fall under the executive

Quis custodiet ipsos custodes? It might have to be Federal, but not the Justice Department. And frankly that function should not even fall under the executive branch, or not completely. I propose a Department of Liberty, lead by a Liberator General that is set up as a check against the Attorney General. It would be tasked with prosecuting crimes committed only by police and government agents, with no power to prosecute private citizens. It would be equipped with its own force of agents who likewise can only arrest police and other agents. The department would also serve as a central voice and funding umbrella for our woefully neglected public defenders. Finally, it would be partly overseen by a Congressional 'grand jury committee', which would be presided over by a sitting SCOTUS Justice on a rotating basis. Federate that model at the state and local level, with appropriate modifications such as actual grand jury oversight.