Corcoran started his legal career at Reid & Priest in New York City. Corcoran moved to Phoenix and joined the law firm of Lewis & Roca in 1959. A few years later, Corcoran joined the Maricopa County Attorney's Office as a criminal prosecutor, where he worked from 1962 to 1964. He later joined the firm of Dushoff & Sacks, which eventually became Dushoff, Sacks & Corcoran. While a partner there, Corcoran served as Arizona Counsel to the American Civil Liberties Union. In 1965, Corcoran was an initial attorney on the landmark constitutional law case Miranda vs. Arizona. As a result of his efforts in the Miranda case, Corcoran received the ACLU Civil Libertarian of the Year Award. Corcoran joined the firm Powers, Boutell, Fannin & Kurn in 1973. He left private practice in 1976 and was appointed to the Maricopa County Superior Court under Arizona's recently enacted Merit Selection System. He served on Superior Court for five years, until he was appointed to the Arizona Court of Appeals in 1981, where he served for seven years.
