In Pennsylvania, those who are accused of certain crimes may be prosecuted in federal court. The federal court system can initiate prosecutions against people accused of violating federal laws. Crimes that violate state law but do not involve the federal government are prosecuted in state courts.
When a federal agency is notified of a crime they believe may involve a violation of federal law, an investigator will be assigned to try to determine whether a crime was committed and, if so, who they believe was involved in its commission. During this stage, the investigator may conduct interviews of the suspect as well as potential witnesses. The case may then be assigned to the federal grand jury, which would then meet to hear the evidence presented by the U.S. attorney tasked with prosecuting the case. The jury will determine whether the accused person will be indicted or if they should return a no true bill. At this stage, the person may be arrested.
The prosecutor will then file the charges in federal court, and a first appearance will be set. If the person was indicted, the defendant will be advised of his or her charges as well as the rights he or she has. If the person was arrested but not indicted, the court will make a probable cause determination. In either case, the judge will decide whether bail is appropriate or if the person is to remain in custody.
At the arraignment, the person will be formally advised and enter a plea to the charged crimes, whether the plea is guilty or not guilty. Following this, their attorney and the U.S. attorney will engage in discovery disclosures and negotiations for possible plea bargaining. The case will then proceed to the entry of a plea and sentencing or to motions hearings and trial.
Source: FBI.gov, "A Brief Description of the Federal Criminal Justice Process", December 08, 2014