Mr. Truong arrives at a courthouse in Alexandria, Va., with FBI agents on Jan. 31, 1978. (Charles del Vecchio/The Washington Post)

David Truong, who was convicted in 1978 of spying for Communist Vietnam in a high-profile courtroom drama that pitted civil liberties against national security concerns in an early test of electronic government surveillance, died June 26 at a hospital in Penang, Malaysia. He was 68.

The cause was a rare form of cancer, his sister Monique Truong Miller said.

Mr. Truong came to the United States from Vietnam to study at Stanford University in the mid-1960s, leaving a country that was mired in war and entering one that would become increasingly divided over its involvement in the conflict.

Mr. Truong joined the antiwar movement in the United States and emerged as a compelling leader, particularly after his father’s unsuccessful bid for the South Vietnamese presidency in 1967. A prominent lawyer, Truong Dinh Dzu supported negotiating with the Viet Cong and subsequently was imprisoned for having “weakened the anti-Communist will of the people and the army.”

In 1968, American newspaper columnist Drew Pearson wrote that “of the several million youngsters in this country urging peace in Vietnam, probably the most effective is David Truong.”

By Mr. Truong’s account, his goals as an activist were, first, to help bring an end to the war in his native country and later, after the U.S. withdrawal from Vietnam in 1975, to improve relations between the nations.

“A Vietnamese who has any feeling for his country . . . cannot help but feel we all struggle together,” Mr. Truong told The Washington Post in 1978. “You cannot help but respect your compatriots who have sacrificed more than anybody to keep your country independent and free.”

Mr. Truong was known and respected on Capitol Hill as a source of information about events in Vietnam, The Post reported. He became engaged in an initiative to provide books, documents and other materials to Vietnamese officials, and through those activities became entangled with a double agent working for the U.S. government.

Mr. Truong was linked to Ronald L. Humphrey, a U.S. Information Agency employee who was seeking the release from Vietnam of his common-law wife and her children and who was supplying Mr. Truong with government documents. Without obtaining a warrant, top Carter administration officials approved electronic surveillance, including a wiretap of Mr. Truong’s phone and a video camera in Humphrey’s office.

In 1978, the two men became defendants in a jury trial at a federal courthouse in Alexandria, Va. — the only espionage trial to emerge from the Vietnam War. They were accused of theft of government documents and a “conspiracy to injure the national defense of the United States.”

A key witness was the double agent, who had acted as a courier. Humphrey did not deny providing government materials to Mr. Truong, and Mr. Truong did not deny having passed them on.

The defense sought to describe the materials as amounting to little more than “diplomatic chitchat,” and both defendants insisted that they intended to aid the ongoing discussions about the normalization of U.S.-Vietnamese relations.

“I’m nobody’s agent,” Mr. Truong told reporters at the time of his trial, “and nobody’s spy.”

Both defendants were convicted and sentenced to 15 years in prison by U.S. District Judge Albert V. Bryan Jr. Their appeals, drawn out over more than three years, challenged the admissibility of the evidence collected from the electronic surveillance because it was conducted without a warrant.

An appeals court upheld the conviction, arguing that “the needs of the executive are so compelling in the area of foreign intelligence, unlike the area of domestic security, that a uniform warrant requirement would . . . unduly frustrate the president in carrying out his foreign affairs responsibilities.”

Mr. Truong began his prison sentence in 1982 and was paroled in 1986. The case, which was decried by civil libertarians, was cited as an example of the need for independent review of electronic surveillance. The Foreign Intelligence Surveillance Act, enacted in 1978, created a special court for such a purpose.

“The recent prosecution against Humphrey and Truong point out the need for this legislation,” U.S. Sen. Edward M. Kennedy (D-Mass.) argued in support of the bill at the time.

David Truong Dinh Hung was born Sept. 2, 1945, in Ho Chi Minh City, formerly named Saigon. His family, he said, was the “first in Vietnam to own a Mercedes.”

Mr. Truong attended French schools before moving to Paris and later to the United States, where he studied economics at Stanford.

In 1981, amid his legal battle, he married U.S. economist Carolyn Gates, with whom he lived in the Netherlands before moving to Penang. He taught economics and worked as an economic development consultant for the European Commission, his sister said. Besides his wife, survivors include several siblings and half-siblings.

“My mind is totally at peace,” Mr. Truong told the judge at the time of his sentencing, “and I’m ready to climb the highest mountain and go down to the lowest peaks no matter how long it takes.”