What is absolutely essential for the federal government to prosecute a crime is a federal statute in the United States Code (U.S.C.) under which the individuals conduct is a crime. Some of the crimes the federal government tends to prosecute are drug offenses, organized crimes, financial crimes, frauds and crimes against the United States such as health care fraud. There are also some crimes that only the federal government has jurisdiction to prosecute these include customs and tax offenses, espionage and treason.
Federal offenses are typically prosecuted by Assistant United States Attorneys who work for United States Attorney's offices whose offices are under the authority of the Department of Justice. There are exceptions such as special proscectors in special cases but that is also beyond the scope of this article.
Federal agencies must be delegated specific authority in order to investigate federal crimes in violation of the USC. Most agencies have investigative elements but do not focus on investigations. There are four primary investigative agencies in the federal government: Secret Service, Federal Bureau of Investigation, Internal Revenue Service Criminal Investigations and Immigrations and Customs Enforcement offices. In some cases, multiple agencies will be responsible for investigating a specific federal crime. It is also important to note, that state investigators can be cross designated as federal agent for investiative purposes. Task Force, which include both state and federal investigators, can also be the designated investigators in a federal criminal case.