"Isn't morphine a very unusual poison?"
"Very; and most inconvenient except in a single, fatal dose, by reason of the rapidity with which tolerance of the drug is established. But we must not forget that slow morphine poisoning might be eminently suitable in certain cases. The manner in which it enfeebles the will, confuses the judgment and debilitates the body might make it very useful to a poisoner whose aim was to get some instrument or document executed, such as a will, deed or assignment. And death could be produced afterwards by other means. You see the important bearing of this?"
"You mean in respect of a death certificate?"
"Yes. Suppose Mr. Weiss to have given a large dose of morphine. He then sends for you and throws out a suggestion of sleeping sickness. If you accept the suggestion he is pretty safe. He can repeat the process until he kills his victim and then get a certificate from you which will cover the murder. It was quite an ingenious scheme—which, by the way, is characteristic of intricate crimes; your subtle criminal often plans his crime like a genius, but he generally executes it like a fool—as this man seems to have done, if we are not doing him an injustice."
"How has he acted like a fool?"
"In several respects. In the first place, he should have chosen his doctor. A good, brisk, confident man who 'knows his own mind' is the sort of person who would have suited him; a man who would have jumped at a diagnosis and stuck
