Most federal criminal cases are tried in US District Court.
Federal.
Generally, federal criminal cases are tried in US District Court.
Federal trial courts almost always have original jurisdiction in the federal system.
Circuit splits -- where two of the federal Circuit Courts of Appeal have decided the same issue of law in contradictory ways. Most cases involve US Constitutional issues.
The US District Court
Most federal cases begin in the district courts.
Federal appellate cases
Most cases reach the US Supreme Court via the US Court of Appeals Circuit Courts, which are part of the federal court system.
State courts, by far, hear more cases per year than all of the Federal Circuits combined.
Cases the US Supreme Court reviews under its appellate jurisdiction usually involve unresolved or unclear constitutional matters that may have resulted in a Circuit split (different decisions on substantially the same question by two different US Court of Appeals Circuit Courts) or a decision from any lower appellate court that is in opposition to the Supreme Court's constitutional interpretation or to established precedents.
The Federal Courts system will only handle specific cases. They handle them if the United States is a party, cases involving violations of federal laws, bankruptcy, copyright issues, patent issues, and maritime law cases.