Thorndyke smiled a little drily. “If you are able,” said he, “to diagnose at sight a potential murderer, your powers are a good deal beyond mine. I should have said that every man has the makings of a murderer, given the appropriate conditions.”
“Should you really?” I exclaimed. “Can you, for instance, imagine either of us committing a murder?”
“I think I can,” he replied. “Of course, the probabilities are very unequal in different cases. There are some men who may be said to be prone to murder. A man of low intelligence, of violent temper, deficient in ordinary self-control, may commit a murder in circumstances that would leave a man of a superior type unmoved. But still, the determining factors are motive and opportunity. Given a sufficient motive and a real opportunity, I can think of no kind of man who might not commit a homicide which would, in a legal sense, be murder.”
“But is there such a thing as a sufficient motive for murder?”
“That question can be answered only by the individual affected. If it seems to him sufficient, it is sufficient in practice.”
“Can you mention a motive that would seem to you sufficient?”
“Yes, I can. Blackmail. Let us take an imaginary case. Suppose a man to be convicted of a crime of which he is innocent. As he has been convicted, the evidence, though fallacious, is overwhelming. He is sentenced to a term of imprisonment—say penal servitude. He serves his sentence and is in due course discharged. He is now free; but the conviction stands against him. He is a discharged convict. His name is in the prison books, his photograph and his finger-prints are in the Habitual Criminals’ Register. He is a marked man for life.
“Now suppose that he manages to shed his identity and in some place where he is unknown begins life afresh. He acquires the excellent character and reputation to which he is, in fact, entitled. He marries and has a family; and he and his family prosper and enjoy the advantages that follow deservedly from his industry and excellent moral qualities.
“And now suppose that at this point his identity is discovered by a blackmailer who forthwith fastens on him, who determines to live on him in perpetuity, to devour the products of his industry, to impoverish his wife and children and to destroy his peace and security by holding over his head the constant menace of exposure. What is such a man to do? The law will help him so far as it can; but it cannot save him from exposure. He can obtain the protection of the law only on condition that he discloses the facts. But that disclosure is precisely the evil that he seeks to avoid. He is an innocent man, but his innocence is known only to himself. The fact, which must transpire if he prosecutes, is that he is a convicted criminal.
“I say, Mayfield, what can he do? What is his remedy? He has but one; and since the law cannot really help him, he is entitled to help himself. If I were in that man’s position and the opportunity presented itself, I would put away that blackmailer with no more qualms than I should have in killing a wasp.”