He earned a B.Sc. and M.Sc. from University College Dublin, in his native Ireland, and then a PhD from Cornell University. He's Professor of Mathematics at Spelman College, in Atlanta, Georgia, where he's been teaching since 1988.
His mathematical interests are broad, and he is a recipient of the Mathematical Association of America's Allendoerfer Award for excellence in expository writing. He published original mathematical card trick principles bi-monthly at MAA.org from 2004 to 2014, and other puzzles of his have appeared in the New York Times. He also blogs as "Maths Colm" at Aperiodical and tweets as @CardColm.