His doctoral dissertation ("John Fitzgibbon, Earl of Clare") was prepared under Professor Ross J. S. Hoffman.
[2] He was married to Julia Ortiz Griffin, a professor of Spanish language and literature at Queensborough Community College, with whom he collaborated on two books.
Griffin authored chapters in several essay collections, including "The Bavarian Protectorate in Greece, 1833-1843" in Studies in Modern History (1968), "Religion and the Expansion of Europe" in Religion in the Making of Western Man (1974), "In Search of the Ultimate Weapon: Military Technology in the Twentieth Century" in Technology in the Twentieth Century (1983), "Voltaire's Soldier of Ill-Fortune: The Lally Affair and the Fate of the Franco-Irish Community" in Voltaire et ses combats: actes du congrès international, Oxford-Paris, 1994 (1997), and a chapter in a Festschrift for his mentor, Ross J. S. Hoffman - "The Forces of the Crown in Ireland, 1798" in Crisis in the "Great Republic": Essays Presented to Ross J. S. Hoffman (1969).
Griffin also contributed articles to the Dictionary of Modern Italian History (1985), both editions of the Encyclopedia of New York City (1995, 2010), and was a member of the editorial advisory board for The New York Irish (1996).
He was a Fellow of the Royal Society of Antiquaries of Ireland, the chairman of the Middle Atlantic Region of the American Committee on Irish Studies, and held memberships in the International Society for Studies of the Eighteenth Century, the North American Conference on British Studies, the American Historical Association, the American Society for Eighteenth-Century Studies, the Military History Society of Ireland, the Canadian Association for Irish Studies, and the Association of Multi-Ethnic Programs (in which he served as Vice President).