Criminal prosecutions typically begin with an investigation conducted by an executive investigative agency. In a federal case, the investigative agency is generally the Federal Bureau of Investigation (FBI) or an executive agency, such as the Environmental Protection Agency (EPA). In a state prosecution, the investigative agency is normally the state or local police.
The investigative entity will examine the facts and circumstances and make a determination if some criminal activity has occurred. During this process, the agency will gather evidence by interviewing witness, reviewing records, and conducting forensic testing. If the investigative agency determines that sufficient evidence exists of criminal activity, the agency will refer the matter to the appropriate prosecutor. If the suspected criminal activity involves the violation of a federal criminal statute, the appropriate prosecutor will be the United States Department of Justice. If the suspected conduct contravenes a state criminal statue, then the police will refer the matter to the state, county, or local prosecutor’s office.