I received a couple of emails asking if the federal system only deals with felonies and why do the Feds prosecute a case instead of the State.
Well, the first question is easy. Federal crimes are grouped into four classifications: Felonies; Misdemeanors; Infractions; and Petty offenses. Within these four classifications, offenses are further organized into classes designated by letter, depending on the length of imprisonment that the court may impose. Since statutes determine the length of the prison term the court will impose, the breakdown of felonies and misdemeanors into classes designated by letter is significant only in application of the sentencing guidelines in determining the length of supervised release after imprisonment. More importantly, the classification of an offense as a felony, misdemeanor, infraction or petty offense affects procedural rights and the sentence the court may impose as well. For instance, the federal government must initiate prosecution of a felony by filing an indictment, unless the defendant waives indictment and elects to proceed by information. The federal government may initiate a prosecution of a misdemeanor by filing an indictment, information or complaint. A petty offense can begin with a citation or violation notice.
As far as the why the Feds take some cases and not others…I don't know. It depends on the specific case. Sometimes it's based on what agency (i.e. DEA, FBI, ATF) is investigating the crime. However, I'm seeing a lot of "multi-jurisdictional" task forces now. Other times it may be as simple as politics and/or resources. Hope this helps.