He entered the private practice of law, first as a solo practitioner, and this in partnership with C. Robert Satti. Entering public service, he served as an assistant prosecuting attorney in the New London Police Court for four years, and was then appointed Circuit Court judge in 1966, and judge of Common Pleas in 1971. In 1973, he was elevated to a seat as a Superior Court Judge, and in 1985, Governor
William A. O'Neill elevated Santaniello to a seat on the state supreme court. Santaniello served until he reached the mandatory retirement age of 70 in 1994, after which he served as a State Trial Judge Referee until his retirement in 2010. ==Personal life and death==