Chief of Police/Sheriff
The Attorney works for the Sheriff and the Attorney that becomes State Police works for the City/State and has a higher degree of understanding of Civil/Criminal Law.
The Federal Police are State Police that know the Civil/Criminal Law of several City/State.
The F.B.I. know Civil/Criminal Law at the City/County Level of several City/County and are assigned to work in the Federal District and must have a permisson slip or writ or warrant from a United States Marshal Police Officer to Enforce the Law outside of the Federal District unless the Crime is in Progress.
The United States Marshal Police Officer is the City/State and County/Federal Authority and an expert at Civil/Criminal Law which is referred to as the Common Law or Constitutional Law because there are many types of Civil and Criminal Law by another Title that must be observed while trying to determine whether a Civil or Criminal Violation has occurred or both have taken place and an arrest and detainment of a suspect is warranted and an apprehension or advisement is made and the Miranda Law should be observed if a suspect is taken into custody.