This is the more necessary inasmuch as we may be easily deceived through apparent motives. “Inasmuch as in most capital crimes two or more motives work together, an ostensible and a concealed one,” says Kraus,[88] “each criminal has at his command apparent motives which encourage the crime.” We know well enough how frequently the thief excuses himself on the ground of his need, how the criminal wants to appear as merely acting in self-defense during robberies, and how often the sensualist, even when he has misbehaved with a little child, still asserts that the child had seduced him. In murder cases even, when the murderer has confessed, we frequently find that he tries to excuse himself. The woman who poisons her husband, really because she wants to marry another, tells her story in such a way as to make it appear that she killed him because he was extraordinarily bad and that her deed simply freed the world of a disgusting object. As a rule the psychological aspect of such cases is made more difficult, by the reason that the subject has in a greater or lesser degree convinced himself of the truth of his statements and finally believes his reasons for excuse altogether or in part. And if a man believes what he says, the proof that the story is false is much harder to make, because psychological arguments that might be used to prove falsehood are then of no use. This is an important fact which compels us to draw a sharp line between a person who is obviously lying and one who does believe what he says. We have to discover the difference, inasmuch as the self-developed conviction of the truth of a story is never so deep rooted as the real conviction of truth. For that reason, the person who has convinced himself of his truth artificially, watches all doubts and objections with much greater care than a man who has no doubt whatever in what he says. The former, moreover, does not have a good conscience, and the proverb says truly, “a bad conscience has a fine ear.” The man knows that he is not dealing correctly with the thing and hence he observes all objections, and the fact that he does so observe, can not be easily overlooked by the examining officer.