“Then why are you accusing me of it?”
“I’m not accusing you of it,” Mason said. “I’m simply telling you that you knew he was dead prior to Tuesday noon, that you covered up that death, and then started getting yourself an alibi. But you’ll find a jury isn’t going to be as charitable as I am.”
“You must be crazy!”
Mason said, “I’m willing to believe that you’re not a murderer, that you shrewdly manipulated things so you could close the sale of that Western Prospecting stock. When you found Tidings was dead, you realized you had to keep his death covered up until you could put through that deal. But what you overlooked, Carl, was that once you started tampering with the facts, a jury would conclude you were guilty of murder.”
Mattern blinked his eyes rapidly. “They couldn’t,” he said.
“Oh, yes, they could, Carl. Let’s suppose, for instance, that you had reason to believe Tidings was going to be at that bungalow on Tuesday morning. Suppose you went out with a brief case filled with mail and documents to get instructions, and suppose you found Tidings lying dead on the bed. You slipped quietly out of the house without anyone seeing you. You knew that the news of his death would put a stop to that stock deal, and so you decided to have it appear that he had died shortly after noon on Tuesday. Fortunately, my telephone call gave you an opportunity for a second string to your bow. I had never heard the voice of Albert Tidings. By a bit of vocal manipulation you were able to leave me with the impression that I had talked with Tidings over the telephone.
“You’re a very clever young man, Mattern, but you must give me credit for knowing something about the psychology of a juror. I’m telling you, Mattern, plainly and frankly, that a jury probably would convict you of Tidings’ murder purely on circumstantial evidence once that chain of facts had been brought to light. The jury would consider that you’d killed him on Tuesday morning… And that would coincide with the findings of the autopsy surgeons.”
Mason devoted his attention to watching the smoke drift up from one end of his cigarette, seeming to dismiss Mattern entirely from his mind.
After a few seconds, Mattern said, “But those things can’t be proven.”
Mason smiled. “Oh, yes, they can,” he said. “I can prove them.”