I am persuaded, after many years' close observation and many years' friendship with criminals, that disease, mental or physical, is a tremendous factor in the causation of crime. The "criminal class" is often spoken of, and it might be supposed that there is a distinct class of people to whom the appellation applies. My experience teaches me that there is no "criminal class," but there are plenty of criminals. The low forehead and the square jaw, the scowling eye and the stubbly beard, do not denote criminality; the receding forehead, the weak eye, and the almost absence of chin, do not indicate criminal instincts. Nothing of the sort. All these things are consistent with decent living, a fair amount of intelligence, and some moral purpose. On the other hand, a well-built body, a well-shaped head, a handsome face, a clean skin, and a bright eye are consistent with the basest criminality. Some of the worst criminals I have met--real and dangerous criminals--were handsome as Apollo. But there does exist a class--and, unfortunately, a very large class--who have very limited intelligence, who appear to be retrogressing physically, mentally, and morally, of whom a large proportion commit various kinds of offences--not from criminal instincts, but from stunted or undeveloped intelligence and lack of reasoning power.
But I am digressing, for it is not my purpose in this chapter to speak of criminals in general, but rather of those whom I have personally met charged with murder, and who were convicted, some paying the full penalty. These I want to consider more fully. From this list I must eliminate man-slayers who had killed in the heat of passion or in a drunken quarrel, for they were not murderers at heart. Their mental condition was understandable, and their bearing while undergoing trial is beside the question. Neither do I wish to include married or single women who had killed their offspring at childbirth or soon after, for they are outside my consideration. But I want to speak plainly about those who had committed prearranged murders, and carried them out with considerable skill.
In refreshing my memory about these, I find that they held several characteristics in common: