John Ritchie III (Jack) was born in Norfolk, Virginia. He studied at the University of Virginia, and he earned a B.S. in 1925. In 1927, Ritchie graduated from the University of Virginia Law School with an LL.B. degree. Jack Ritchie began and ended his long, outstanding career in legal education at the University of Virginia. A member of "The Celebrated Class of '27," he was Book Review Editor of the Virginia Law Review and member of Order of the Coif, Phi Beta Kappa, the Raven Society, the Jefferson Literary Society, Alpha Kappa Psi, and Omicron Delta Kappa. In 1931, he earned a J.S.D. from Yale University. After practicing law briefly in 1927 and 1928, Ritchie taught law at Furman University, Washington University in St. Louis, and University of Maryland before returning to teach at his alma mater in 1937. During World War II he served as Colonel in the Judge Advocate General's Corp, and Ritchie was awarded several military honor decorations.

In 1952, Ritchie left Virginia to serve as Dean at Washington University in St. Louis and later, he was Dean at the University of Wisconsin. In 1957, he became Dean at Northwestern University Law School where he remained until 1972. He became the first John Henry Wigmore Professor of Law at Northwestern in 1966. Jack Ritchie was a well-loved dean at Northwestern. According to The Northwestern Reporter, he possessed "an unusually happy blend of wisdom, patience, and warmth." During his deanship, the Northwestern University faculty grew in size and reputation, and new facilities were constructed. "His years at Northwestern will be remembered particularly for his devotion to students and for the strengthening of the School's relationship with alumni . . ." In addition to his administrative duties, Ritchie taught trusts and estates, and along with co-authors Neill Alford and Richard Effland, wrote the casebook, Decedents' Estates and Trusts, which appeared in 7 editions from 1955 until just after his death in 1988. He was President of the Association of American Law Schools, national President of the Order of the Coif, member of the American Law Institute, and Life Fellow of the American Bar Foundation. At the age of 68, Ritchie had to retire from the deanship at Northwestern. Ritchie returned to the UVA Law School and he taught full-time for 2 more years. Afterwards, he became the UVA Law School Scholar-in-Residence. In addition to Trusts and Estates, Ritchie’s courses included Future Interests, Wills & Administration, and Fiduciary Administration. An extraordinarily active man, Ritchie was not entirely "in residence" because in the next 3 years he visited at the University of Tennessee, the University of Oklahoma, and the College of William and Mary. In the mid-1970s, he worked on a history of the University of Virginia Law School, The First Hundred Years, which was published in 1978. For the rest of his life, Ritchie remained active in the American Bar Association and the Virginia Bar Association, worked occasionally as a consultant in trusts matters, and served on the board of The Foundation Press.