He graduated from the McGeorge School of Law of the University of the Pacific with honors in 1974 and was admitted to the California bar in 1974 and the Hawaii bar the next year.
Lilly was a Hawaii Deputy Attorney General from 1975 to 1979 and practiced in San Jose, California from 1979 to 1981.
In 1981 he was named First Deputy Attorney General in Hawaii.
Lilly was appointed Hawaii Attorney General by Governor George Ariyoshi in June 1984.
[1] Lilly returned to private practice in 1985, and was succeeded by First Deputy Attorney General Corinne Watanabe.