Federal criminal charges are accusations filed in federal court, by a federal grand jury or federal prosecutor, asserting that a particular person or entity has violated a federal law, which carries penal sanctions. Federal criminal charges are relatively rare as the vast majority of crimes in the United States are prosecuted under state law, in state courts. Nevertheless, federal criminal charges have commanded sustained public and scholarly attention. This entry briefly surveys the history and evolution of federal criminal enforcement and highlights major debates in the field surrounding enforcement, sentencing, and the concept of mens rea (i.e., requisite mental state of the accused with regard to awareness of wrongdoing for the alleged criminal act).