Robert K. Carr, 71, an educator, author and authority on constitutional law and civil liberties, died of a brain tumor Wednesday in a nursing home in Elyria, Ohio.

He was president of Oberlin College in Ohio from 1960 to 1970 after 23 years of teaching at Dartmouth College in New Hampshire, from which he graduated in 1929 and where he was elected to Phi Beta Kappa.

Dr. Carr went on to earn a master's degree and doctorate from Harvard University. He also held a number of honorary degrees.

In 1947, while teaching government at Dartmouth, Dr. Carr served as executive director of President Truman's Commission on Civil Rights and was the principal author of the federal report "To Secure These Rights."

He also wrote three books, "The Supreme Court and Judicial Review," "Federal Protection of Civil Rights," and "The House Committee on Un-American Activities." He was coauthor of four others, "American Democracy in Theory and Practice," "Civil Liberties Under Attack," "Foundations of Freedom" and "Aspects of Liberty."

After he left Oberlin, Dr. Carr joined the American Council on Education as an executive associate, directing a study of the future of the academic profession. He returned to Oberlin in 1975 to teach constitutional law.

He was a former general secretary of the American Association of University Professors and a trustee of the Carnegie Foundation for the Advancement of Teaching. He served as a consultant to the Association of Governing Boards of Universities and Colleges.

Dr. Carr was active in the American Council on Education and was a member of the Advisory Committee on Higher Education of the Department of Health, Education and Welfare.

He is survived by his wife, Olive Grabill Carr, of the home in Oberlin; three sons, Norman, of Akron, Ohio, Elliott, of Pembroke Mass., and Robert, of New Canaan, Conn., and seven grandchildren.