Justin E. O'Donnell, 68, a justice of the peace in Arlington and a former intelligence officer who served behind enemy lines in World War II and held several important posts during the most difficult years of the Cold War, died of a brain tumor Aug. 24 at Arlington Hospital.

Mr. O'Donnell's career took him to Latin America, the Middle East, Europe and Asia. He was the station chief of the CIA in Bolivia, Holland, Thailand and Turkey. He also had several assignments in the upper regions of the intelligence community in Washington. His foreign languages included French, Turkish and Thai.

Associates described him as a man who understood the function of foreign intelligence operations and the relation of these operations to the rest of the government and the principles of the Constitution. A case in point, they said, was his testimony in 1974 before a congressional committee chaired by Sen. Frank Church (D-Idaho) that investigated CIA plots to assassinate unfriendly foreign leaders.

He was asked about agency operations in the Congo, now Zaire, in the turbulent years after it gained independence from Belgium in 1960. The CIA considered killing Premier Patrice Lumumba. Mr. O'Donnell said he opposed the operation and had told Richard Helms, then deputy director of the CIA, that the U.S. government could not condone political murder. Lumumba later was killed by other Congolese who acted without U.S. involvement.

Mr. O'Donnell, who lived in McLean, was born in Wilkes-Barre, Pa. He graduated from Bucknell University and the Dickinson School of Law. He began his government career as an Army private in World War II. He was commissioned when he was assigned to the Counter-Intelligence Corps, with which he served in Panama.

Later, he was transferred to the Office of Strategic Services, a predecessor of the CIA, and was sent behind enemy lines in Europe. He retired from the Army as a captain and in 1947 joined the Central Intelligence Group. Later that year, the CIG became the CIA.

Mr. O'Donnell was station chief in La Paz, Bolivia, in 1947 and 1948. From 1949 to 1952, he was a consultant to the Turkish government. From 1952 to 1956, he was station chief in Holland and Thailand. From 1957 to 1961, he held the same job in Turkey. These were the years when U.S. missiles were stationed in Turkey and the country was being used as a base for U-2 spy plane flights over the Soviet Union.

From 1962 to 1964, Mr. O'Donnell was project director of the Special Operations Division in the Office of the Secretary of Defense and the International Security Agency. From 1965 to 1967, when he retired from the government, he was the senior Defense Department faculty adviser at the National Intelligence Defense Seminar at the Foreign Service Institute.

Mr. O'Donnell then became a justice of the peace in Arlington and continued that work until his death.

He was a member of St. John's Catholic Church in McLean.

Survivors include his wife, Jill O'Donnell of McLean; two brothers, Roger, of Chicago, and Edmond, of Wilkes-Barre, and two sisters, Geraldine Corcoran of Chicago and Ruth Woehrle of Plains, Pa.