Marvin W. Humphreys, 44, a Foreign Service officer who shot himself to death at his home at Lake Barcroft on Sept. 17, was the State Department's director of nuclear policy and operations.

Fairfax County police said Mr. Humphreys took his own life after fatally shooting his wife, Lynda H. Spering Humphreys.

Mr. Humphreys, who was born in Washington, graduated from Haverford College in 1958 and earned a master's degree in international relations from the Fletcher School of Law and Diplomacy at Tufts University in 1959. He joined the Foreign Service in the same year.

In 1970, he earned a master's degree in international relations from the Johns Hopkins School for Advanced International Studies in Washington.

In 1978, Mr. Humphreys was assigned to the Arms Control and Disarmament Agency and became director of the nuclear policy and operations office in the State Department's bureau of politico-military affairs. He recently returned from Geneva, where he was State's senior representative on the U.S. delegation to the Non-Proliferation Treaty Review Conference. His foreign languages were French and Italian. Colleagues regarded him as an expert in political military affairs.

Survivors include two sons, David, a student at the Massachusetts Institute of Technology in Cambridge, Mass., and Steven, a student at Yale University in New Haven, Conn.; his mother, Elizabeth of Washington, and a brother, Dr. Charles Humphreys, a physician, of Chevy Chase.

The family suggests that expressions of sympathy be in the form of contributions to the Foreign Service Scholaarship Fund, c/o The Association of American Foreign Service Women, Department of State, Washington, D.C., to the Dean's Fund, Yale University, New Haven, Conn., or to the MIT Scholarship Fund, Cambridge, Mass.