Members of the United States military are subject to a court martial when they commit offenses that are prohibited by the Uniform Code of Military Justice (UCMJ). Offenses under the UCMJ may be offenses that are either federal crimes, such as drug offenses and theft of government property, or they may be offenses that become federal offenses because they are committed on a United States military installation.

A court martial is conducted by each particular branch of the United States military, that is, the Air Force, the Army, the Navy, or the Marine Corps. Because the particular branch is part of the Department of Defense, the court martial is considered as being conducted by the Department of Defense. The Department of Justice prosecutes federal criminal offenses.

The Department of Defense and the Department of Justice have concurrent jurisdiction over criminal offenses that involve the Department of Defense, that are committed on military installations, and that are committed outside military installations by military personnel. The Department of Defense and the Department of Justice have therefore entered into a Memorandum of Understanding with regard to the investigation and prosecution of such offenses.

The Memorandum of Understanding provides that the Department of Defense will refer all investigations to the Federal Bureau of Investigations (FBI) when an investigation involves allegations of corruption within the Department of Defense, such as bribery and conflicts of interest. The investigation may involve military personnel or civilian personnel within the Department of Defense. The FBI must promptly notify the Department of Defense if it will investigate the allegations. Once the investigation has been referred to the FBI, the Department of Defense must obtain the approval of the FBI or the Department of Justice before it may initiate an independent investigation under the UCMJ.

If a fraud has been committed against the Department of Defense, such as the theft or embezzlement of Department of Defense property, the Department of Defense has primary investigative responsibility for the offense. If the Department of Defense determines that the offense warrants federal prosecution, it will confer with the Department of Justice and the FBI. The Department of Defense and the Department of Justice will decide which department will continue with the investigation.

A criminal offense that is committed on a military installation is generally investigated by the installation's particular military branch. If the offense is committed by a person who is subject to the UCMJ, that is, by a service member who is subject to a court-martial, the military will prosecute the offense. If the offense is committed by a person who is not subject to the UCMJ and who is not subject to a court-martial, the Department of Defense will refer the offense to the Department of Justice for investigation and prosecution.

When a criminal offense is committed outside a military installation by a member of the military, which offense is subject to prosecution under the UCMJ, the Department of Defense shall investigate and prosecute the offense. If the offense is related to scheduled military activities outside the military installation, such as maneuvers, the offense shall be treated as if it were committed on the installation. The Department of Defense shall investigate and prosecute the offense. If the offense is a federal offense and is not an offense under the UCMJ, the Department of Defense shall refer the offense to the Department of Justice for investigation and prosecution.

If the Department of Defense conducts its own investigation, which investigation may lead to a prosecution in a federal district court, the Department of Defense shall conduct the investigation in accordance with the guidelines of the Department of Justice.

The Department of Defense and the Department of Justice may conduct joint investigations under certain circumstances, such as undercover operations. The joint investigations shall also be conducted in accordance with the guidelines of the Department of Justice.