Doar prosecuted the federal case for civil rights violations against the people who were accused of murdering Andrew Goodman, James Chaney and Michael Schwerner, young civil rights workers in Mississippi. He had earlier contributed to drafting the Civil Rights Act of 1964, which Lyndon Johnson signed to try to enforce constitutional rights for all citizens. In March 1965, Doar was the first to arrive in Montgomery, Alabama, during the third of the Selma to Montgomery marches. He walked into Montgomery half a block ahead of the march in his capacity as Assistant Attorney General.