Truong Dinh Hung (defendant) was a Vietnamese citizen who came to the United States in 1965 and remained active in politics surrounding U.S. involvement in Vietnam. In 1976, Truong met Vietnamese-American Dung Krall. Knowing Krall had a close relationship with the Vietnamese community in Paris, Truong asked Krall to carry packages to representatives of the Socialist Republic of Vietnam there. Inside of these packages were copies of classified documents belonging to the U.S. government related to its activities in Southeast Asia. Truong obtained these documents from Ronald Humphrey (defendant), a U.S. Information Agency employee. Unbeknownst to Truong, however, Krall was a confidential informant for the Central Intelligence Agency (CIA) and Federal Bureau of Investigation (FBI), reporting to the agencies and handing the packages over for inspection before she brought them to Paris—an arrangement that lasted from September 1976 to January 1978. When it Truong’s activities were discovered, the FBI sought Truong’s source of information. To do so, the government organized widespread surveillance of Truong through tapping his phone and bugging his apartment, which continued for over 250 days. The government never acquired any warrant or court authorization for the taps. On July 20, 1977, the Criminal Division of the Justice Department began to put together a criminal prosecution against the defendants. On January 31, 1978, Humphrey and Truong were arrested. A district court ruled that evidence obtained by surveillance after July 20, 1977, when the official criminal investigation commenced, should be excluded at trial, and that all evidence secured before that date could be rightfully introduced at trial. Humphrey and Truong were subsequently convicted. The two then challenged their convictions, arguing that the surveillance conducted violated the Fourth Amendment.