Im currently in the last year of Law School, not in the US. I got accepted on a public tender last year for precinct chief but I have been working on the judiciary police since I was 18(21 now), here in my country the precinct chief is responsable for the first "phase" of the criminal accusation, wich is the investigation of the crime, then this investigation is sent to the district attorney so he can press accuse the indicted. We pretty much conduct investigations on crimes that happened and ongoing crime. We are a essential branch of the criminal justice here and we work closely to the district attorney/state attorney. Kinda different from the US, so it might be hard to understand.