Fred M. Vinson Jr., 57, a Washington lawyer and former assistant attorney general of the United States, died Nov. 21 at Sibley Memorial Hospital after a heart attack. He lived in the Westmoreland Hills section of Bethesda.

He was assistant attorney general, in charge of the Justice Department's criminal division, from 1965 to 1969. During those years, he successfully argued before the U.S. Supreme Court the jury-tampering conviction of former Teamster President James R. Hoffa.

Mr. Vinson also supported the Johnson administration in its opposition to such matters as antiriot legislation, the use of draft reclassification to punish Vietnam war protesters, and the so-called "get-tough" crime legislation for the District of Columbia.

Since leaving Justice, he had been a senior partner in the firm of Reasoner, Davis & Vinson, which he had first joined in 1954. Mr. Vinson also was chairman of the board of trustees of the D.C. Public Defenders Service from 1976 to 1978. Also during the 1970s, he had chaired the committee on admissions and grievances, and served on the board of professional responsibility of the U.S. Circuit Court for the District of Columbia.

He was president of the D.C. Bar Association from 1971 to 1972, and served in the American Bar Association's House of Delegates from 1971 to 1974. He was a fellow of the American Bar Foundation and member of the American College of Trial Lawyers.

Mr. Vinson also had been active in civic and historical organizations, including the Board of Trade. He was general counsel of the 1961 Inaugural Committee, and had served as chairman of the board of the Supreme Court Historial Society. His father, the late Fred M. Vinson Sr., was chief justice of the United States from 1946 to 1953.

Fred Moore Vinson Jr. was born in Louisa, Ky., on Apr. 3, 1925, and was a graduate of Wilson High School in Washington. He attended Washington and Lee University, where he earned undergraduate and law degrees, was a star baseball player, and was elected to Phi Beta Kappa and the Order of the Coif. He served in the Army Air Forces during World War II. He was admitted to the District Bar in 1951.

He was a past president of Burning Tree Club, and had belonged to the Metropolitan and Chevy Chase clubs.

Survivors include his wife, the former Nell P. Morrison, a son, Fred M. III, and a daughter, Carolyn P. Vinson, all of Bethesda, and his mother, Roberta Vinson of Washington.