Charles J. Fanning, 71, a former federal prosecutor who retired in 1988 after 12 years as special assistant to the administrator of the Drug Enforcement Administration, died of a brain aneurysm Oct. 2 at Inova Fair Oaks Hospital.

Mr. Fanning began his career in 1958 as a law clerk for a U.S. District judge in New York City. Four years later, then-Attorney General Robert F. Kennedy appointed him an assistant U.S. attorney.

After a few years in New York City, he transferred to the U.S. attorney's office in San Diego and led a special narcotics task force that handled investigations in five states.

In 1976, he won the conviction of a drug trafficker in Guam for the murder of a DEA agent. After that case, which drew praise from Justice Department officials, he was summoned to Washington to serve as an adviser to the then-administrator of the DEA, Peter Bensinger.

Mr. Fanning, a McLean resident, was a native of New York City and a graduate of Long Island University. He served in the Army in 1946 and 1947 and received a law degree in 1958 from Fordham University.

As a Mason for the last nine years, he had volunteered with its blood donor drives and programs to provide school clothes for poor children. He sang with the Singing Capital Chorus and performed in many charity and community events.

An avid golfer, he was a member of the Kenwood Golf Club. His other interests included gourmet cooking and gardening.

His wife, Ann Patricia Carden Fanning, died in 1973. Survivors include two children, Charles J. Fanning Jr. of San Francisco and Julianne Brykczynski of Fairfax; three brothers; three sisters; and two grandchildren.