Professor Mahon is a former law clerk to Justice Tom C. Clark, Supreme Court of the United States. After practicing law in New York City, he taught at Fordham Law School, served as chief counsel to the New York State Governor's Special Committee on Criminal Offenders, and then as the founding Dean of the Hofstra School of Law from 1968 to 1973. He taught at the University of Texas Law School as the Wright C. Morrow Visiting Professor, and was executive director and special assistant attorney general for the 1975 Meyer Investigation of the Attica Prosecutor's Office. From 1983 to 1996, he served as member or chairman of the Nassau County Board of Ethics. Written for a special committee of the Association of the Bar of the City of New York, his book Mental Illness, Due Process and the Criminal Defendant has been widely cited and quoted by federal and state courts, including the U.S. Supreme Court. In addition, he has written a monthly column on developments in commercial law for the New York Law Journal, and is a member of the American Law Institute. He is a member of the Uniform Commercial Code Committee of the American Bar Association's Section of Banking, Business and Corporation Law.