Beginning in 1955, when he came to Washington, Mr. Barrett was one of the first civil rights lawyers in the government. He was part of the Justice Department’s Civil Rights Division when it was created in 1957 and had a major role in many celebrated legal landmarks, including the desegregation of Little Rock’s Central High School in the 1950s, James Meredith’s enrollment as the first African American student at the University of Mississippi and the integration of interstate buses by the Freedom Riders of the early 1960s.
Mr. Barrett, who was 89 when he died May 28 at Howard County General Hospital of pneumonia, seldom made headlines on his own. But for more than a decade, he was at the forefront of perhaps the most momentous movement for social change in the nation’s history.
“He made an enormous impact as a government lawyer in enforcing the civil rights laws,” John Doar, the top lawyer in the Civil Rights Division in the 1960s and recipient of the Presidential Medal of Freedom last month, said in an interview. “I had such confidence in him. I felt he had a much better grasp of civil rights law than I did.”
Mr. Barrett was an assistant district attorney in Oakland, Calif., when a former colleague invited him to join the Justice Department. Civil rights law was still in its infancy.
In 1957, Mr. Barrett worked alongside Thurgood Marshall — who later became the first African American justice of the U.S. Supreme Court — on the case in Little Rock, in which the governor used the National Guard to prevent the school from integrating.
Often, however, Mr. Barrett was on his own, exploring a new legal field with few precedents. Armed with little more than the force of law and sheer moral courage, he performed much of his work in the face of intimidation, anger and fear.
At home in Chevy Chase, Mr. Barrett’s children knew little about their father’s contributions to civil rights.
“He didn’t talk about that,” his son David Barrett said. “That’s something he would downplay.”
St. John Barrett was born May 21, 1923, in Santa Rosa, Calif., where his father was a lawyer. The younger Mr. Barrett — whose first name derived from his mother’s maiden name — grew to be a lanky 6-foot-4 and was known from an early age as “Slim.”
He graduated from Pomona College in Claremont, Calif., in 1943. He contracted meningitis, which kept him out of the military during World War II, and he worked as an engineer at an aircraft plant in Santa Monica, Calif. He graduated from law school at the University of California at Berkeley in 1948.
When he traveled overseas in 1951, Mr. Barrett carried with him a letter of introduction from Earl Warren, the governor of California, who became chief justice of the Supreme Court in 1953. Both men were Republicans and had worked as prosecutors in Alameda County, Calif.
At the Justice Department, Mr. Barrett handled voting rights and school desegregation cases — including a famous episode in Virginia in which Prince Edward County officials closed the public schools for five years rather than comply with an order to desegregate.
Although he said he never felt in personal danger, Mr. Barrett was a firsthand witness to how the racial order of the South was enforced by violence.
In 1962, he accompanied Meredith as he tried to enroll at the all-white University of Mississippi
. State troopers formed a cordon through which Meredith and Mr. Barrett had to pass.
When Gov. Ross R. Barnett (D) refused to admit Meredith to the university, Mr. Barrett told the governor that he was violating a federal court order. As they left the campus in a car, Mr. Barrett was seated next to Meredith in the back seat.
“A pretty coed stood a couple of feet from my closed car window,” Mr. Barrett recalled in a 2009 memoir. “She was looking directly at me shouting something I could not distinguish, her face contorted with rage as she shook her middle finger at me.”
Later, two people were killed in riots on the campus, and Barnett was found guilty of contempt of court. Troops were dispatched to restore order before Meredith was able to attend class.
In 1963, Mr. Barrett handled the case of Fannie Lou Hamer, a 45-year-old civil rights worker who had been arrested with another black woman in Winona, Miss. In jail, the women were forced to lie on their stomachs, raise their dresses and endure a savage beating with a lead pipe wrapped in leather.
Days later, they appeared at Mr. Barrett’s office in Washington.
“They could barely walk,” he wrote in his memoir. They brought their blood-soaked underclothes with them in plastic bags.
Mr. Barrett arranged with the FBI to have the women’s injuries photographed. He included the pictures and the underwear as evidence when he drafted a complaint charging the sheriff with depriving the women of due process of law.
In another case, Mr. Barrett brought charges against Lester Maddox, a Georgia restaurant owner who later became governor, for refusing to serve black customers.
Mr. Barrett also investigated the 1965 murder of Viola Liuzzo, a mother of five from Michigan who had driven to the South to help in the civil rights movement. After she gave a black civil rights worker a ride, she was followed for 20 miles down an Alabama highway by a car carrying four members of the Ku Klux Klan. One of them fired a sawed-off shotgun through the driver’s window of Liuzzo’s car, leaving her dead.
One of the Klansmen was an FBI informant. Mr. Barrett interviewed him about the killing, but Alabama juries exonerated his companions of murder. Three Klansmen ultimately went to federal prison for 10 years for conspiracy. The fourth man in the car — the federal informant — entered the witness-protection program.
“Dad felt zero fear going into those situations in the South,” James Barrett said of his father. “It just didn’t bother him.”
During his 10 years in the Civil Rights Division, Mr. Barrett worked for three attorneys general, including Robert F. Kennedy. On the day Kennedy resigned in 1964, he sent a note to Mr. Barrett, crossing out “Dear St. John” to write “Slim.”
“When we look back four years and see how much was needed to be done, and now how much has been accomplished,” Kennedy wrote, “you can take great satisfaction in having made an important contribution to the country in a time of maximum need. President Kennedy would have wished to thank you for that — and for your loyalty.”
Mr. Barrett left the Justice Department in 1967 to become deputy general counsel at the old Department of Health, Education and Welfare. He went into private practice in 1977 and retired in 2002. He moved from Chevy Chase to Silver Spring and, last year, to Ellicott City.
Survivors include his wife of 52 years, Elisabeth Fuchs Barrett of Ellicott City; five children, Susan Borchers of Ellicott City, David Barrett of Bethesda, James Barrett of Garrett Park, Robert Barrett of San Francisco and Anna Hodgson of Washington; a sister; and 13 grandchildren.
In the late 1990s, Mr. Barrett received a lifetime achievement award for his work in civil rights. A decade later, when he wrote his memoirs, called “The Drive for Equality,” he said he felt a “warm satisfaction” about his early accomplishments.
It was, he wrote, “the best job a lawyer could possibly have.”