He had dark hair and striking blue eyes, once likened to the eyes of a Mesmerist. "The eyes are very big and wide open," a physician named John L. Capen later observed. "They are blue. Great murderers, like great men in other walks of activity, have blue eyes." Capen also noted thin lips, tented by a full dark mustache. What he found most striking, however, were Holmes's ears.
p. 35 of The Devil in the White City by Erik Larson